How Does Propolis Work
We have seen that propolis fulﬁls a comprehensive and important role in maintaining the health of the bee colony. We have also seen in our panoramic sketch of the history of its traditional use by man as a medicine that it has had a wide range of powerful and medicinal uses. It’s time now to ask how it works. What is it in propolis that does the business?
In modern pharmacology we are used to asking this question and getting a reasonably straightforward answer. It is the complex action of a limited number of active ingredients or elements within the product, sometimes even just the one. Modern medicine has been dominated by our search for so-called active ingredients— those speciﬁc, unique and hopefully patentable biochemicals which hold the key to the destruction of a particular microbe, virus or fungus. Modern drug-based medicine invokes a reductionist mind- set which believes it can pin every element down as having a speciﬁc identiﬁable function rather than a belief in and under standing of the way whole products operate synergistically. By understanding the separate parts it is believed we can replicate them, take out the bits we want and throw away those we don’t need. Rudolf Steiner,1 a natural scientist at the turn of the century, grasped the way modern science was going at an early stage of its development.
A pupil of the famous Bunge, the Professor of Physiology, made experiments in feeding mice with milk. The mice had a good time of it; they throve extremely well when they were fed on milk. So now he made the experiment in another way. He said to himself: the mice throve splendidly on milk; milk consists of casein, fat, sugar and salts. Consequently I shall give some mice casein, fat, sugar and salts; . . . And behold! When he gave the mice casein, fat, sugar and salt they died within a few days. They got the same things but they all died.
Dr Peter Mansﬁeld,2 the founder of Good Health Keeping, has worked most of his life as a general practitioner in England. Disenchanted with what he sees as an obsession with negative health, i.e. concern only with dealing with ill-health, he now runs a natural alternative to the National Health Service, in Louth in Lincolnshire. Seventy years after Rudolf Steiner’s observation he makes a similar observation.
‘The fact is Western therapeutics is driven by the need to discover more and more patentable new chemicals, each of which gives its inventor a head start over its rivals. Natural medicines are out, however cheap and effective they are, they cannot be patented. So companies are driven to dissect natural products looking for an ingredient for a puriﬁcation method they can make their own.’
Referring speciﬁcally to propolis he says:
It is unlikely that such an analytical approach will ever prove successful . . . analysis of this material yields a plethora of aromatic organic compounds and bioﬂavonoids in varying concentrations, none of which individually appears to be the essential ingredient (my emphasis). To the altruistic scientist this does not much matter; he is happy to work with a crude alcoholic extract of the whole propolis material. But it frustrates the hunt for patents.
Some of its properties defy not just chemical analysis but the very principles of chemistry. The interior of the beehive is a remarkably clean, sterile place—far more so than the surgical departments of hospitals. Yet this is achieved not by dosing all the bees individually, nor by lining the entire honey comb, but by an outer skin of propolis alone.
What is in propolis?
Personal research at the International Bee Research Institute in Cardiff, turned up 52 research papers produced between 1973 and 1994 exploring the chemical constituents of propolis and a further 600+ exploring the many-sided properties of propolis. Propolis contains some 150 different biochemical entities and more are being discovered every year. The chemical composition of propolis will vary according to the local ﬂora, the climatic zone, and the type of bees collecting it, the season it is collected in and even the time of day it is collected. I am not a scientist, let alone a pharmacologist, but it is clear to me reading these papers that we have only just begun to understand the operation of some of the principal groups of elements in the propolis collected in mainly temperate climatic zones. Propolis collected in tropical zones contains sometimes radically different concentrations of biochemicals and yet still has a range of similar pharmacological properties.
If we are still not sure what is in propolis, how can we expect to understand what some 150 individual biochemicals are doing, let alone how those biochemicals are acting synergistically? This is not an argument for not doing the science; rather, it is an argument for humility and for not rejecting something because we do not know exactly how it works. It is in this context that we turn to exploring those groups of elements and single elements, which have emerged as playing a crucial pharmacological role in relation to particular medicinal properties of propolis. Broadly speaking these fall into four groups.3
These are principally esters of fatty acids and long chain hydrocarbon alcohols which are largely inactive chemically although extensively used in cosmetics. However, where propolis is used medicinally it is often in an extract from which the beeswax has been removed.
The characteristic aroma of propolis is due mainly to these substances, mainly terpenes, although propolis found in temperate zones contains comparatively small amounts of them and very little is known about their biological activity. Propolis in tropical zones however contains far more and are known to have signiﬁcant biological activity.
These include caffeic acid phenylethylester or CAPE which research has shown to produce some of the medicinal properties.4
These are found in nearly all ﬂowering plant species. Dozens of these have been isolated in propolis, of which pinocembrin and galangin are thought to be most important. It is interesting to note, however, that ﬂavonoids in plants show subtle biochemical changes when they appear in propolis, which is thought to be as a result of the enzymic action of the bee’s salivary glands. Flavonoid content in propolis can range from 10–20 per cent and form the largest single biochemical group within propolis. It is the ﬂavonoid content of propolis, which has given rise to the most concerted interest on the part of researchers.
Flavonoids in European propolis can comprise up to 20 per cent of its weight. There is a major difference between the ﬂavonoids found in plants and those found in propolis. Those found in propolis are not glycosides, that is. They do not have sugars attached to their biochemical structure as those found in plants do. The difference may well be due to the way the bee ‘process’ these ﬂavonoids through the secretion of enzymes. The fact is, they are changed, and this may well explain some of the unique therapeutic qualities of propolis.
There has been some debate concerning the presence of ﬂavonoids in other products from the beehive i.e. in the pollen and honey. Sabatier and others conducted some research at the University of Coimbra, Portugal, in 1995 and found that the total ﬂavonoid content in pollen was 0.5 per cent, honey 0.006 per cent and in propolis 10 per cent.
Bioﬂavonoids have created considerable interest worldwide over the last twenty years. In 1974 naturopathic physician Paavo Airola,5 was able to claim that ‘over ﬁve hundred scientiﬁc papers on bioﬂavonoids have been published in reputable medical journals around the world. Clinical reports have shown that bioﬂavonoid therapy is effective in such diversiﬁed conditions as rheumatic fever, spontaneous abortions and miscarriages, high blood pressure, respiratory infections, haemorrhoids, cirrhosis of the liver.’6 By the 1990s scientiﬁc interest had increased dramatically.
Carlson Wade, in his excellent introduction to propolis, Propolis: Nature’s Energizer published the details of a personal interview with Bent Havsteen MD of Kiel University, who has published extensively on the importance of ﬂavonoids in propolis. This interview provides some clear and dramatic insight into the role of bioﬂavonoids and through it the dynamic role of propolis as a whole.
Bioﬂavonoids in propolis have a protective effect on virus infections. Let me explain. Viruses are enclosed in a protein coat. As long as it remains unbroken, the infectious and dangerous material remains imprisoned and is harmless to the organism. We have found that an enzyme, which normally removes the protein coat, is being inhibited; thus, dangerous viral material is kept locked in. The protein coating around the virus is maintained by the bioﬂavonoids in propolis; these ﬂavonoids keep the virus inactive. It is the same as being immune to the virus but only with the presence of bioﬂavonoids as in the propolis.
This provides us with a fascinating and graphic illustration of the role of ﬂavonoids in propolis. When I ﬁrst read it in 1992 it reminded me vividly of the way in the bees themselves deal with intruders into the hive. They surround and seal up the source of infection with propolis in just the same way as the bioﬂavonoids seal in the virus, preventing it from entering into the body. In this way we see that the virus, rather than being destroyed, is disabled, a process which also strikes me as a metaphor for the difference between natural and allopathic medicine. Natural (whole) medicine is about working with and maintaining the ecology and balance of the body, rather than destroying diseases. A strong immune system is one where the creative and destructive forces are kept in balance, not where one element must defeat the other.
Dr Havsteen continues: ‘The action of propolis bioﬂavonoids is almost identical with that of aspirin. They block the same enzyme. But propolis has an advantage over aspirin because it has no side effects.’ For example, in the case of sore throats caused by inﬂamed and infected mucous membrane, ‘the bioﬂavonoids in propolis actually block the building of prostaglandins (which cause the pain). It is like building immunity to sore throats and related winter ailments.’8 Sticking with the theme of immunity, Dr Havsteen tells us that bioﬂavonoids stimulate the white bloods cells and lymphocytes into producing interferon the natural protein substance now recognised as central to a healthy immune system.
Bioﬂavonoids work the same way in preventing allergies.
Histamine and serotonin are tissue hormones. They remain in the master cells. But when an allergen binds itself to the outside of the cell, these two substances leak out and cause an allergic reaction. The trick is to block the leakage of these substances. We have found that this can be done with the use of bioﬂavonoids in propolis. They block the acids that would break into the cells and cause the release of the allergy- causing substances. Again we see that propolis can create this form of built-in immunity.
Once again the image is of a substance strengthening a natural balance rather than destroying or removing any single element.
Finally, Havsteen provides us with some insight into an area we will look at later, that is the role of propolis in treating dental problems, in particular those caused by inﬂammation of the gums, mouth ulcers and erosion and infectious bleeding of the gums and tissues that line the mouth. As we have seen, the bioﬂavonoids in propolis block the production of prostaglandins which cause decomposition. ‘But there is another beneﬁt. The bioﬂavonoids stimulated enzyme formation to fortify the walls of the blood vessels in the gums. In this way, we have a two-pronged or multi- pronged attack on the diseased area of the mouth.’
The key words here are blocking, sealing in, locking in, fortifying and building up. Bioﬂavonoids appear to have a general protective function within the body. Perhaps more than any other factor this explains the incredible range of properties possessed by propolis, properties we have come to recognise only as single speciﬁc pharmacological effects: antibiotic, anti-inﬂammatory, anti-fungal, etc. Our imaginations rebel against the idea of a single product, which wraps all these functions into one. But should it? Perhaps what we have done with ‘active ingredient medicine’ is to identify only the ﬁghting force against disease, the armed element, and forget the diplomats, the ﬁeld surgeons, and the myriad of other hidden elements that go into ﬁnding a long-lasting and whole solution.
The following pharmacological properties have been attributed to propolis in research carried out over the last 30 years.
- antioxidant and preservative
- antiviral and immuno-stimulant effects.
This is one of the most intriguing and least understood properties of propolis. Anyone who chews good quality raw propolis for any period will soon recognise the numbing effect it produces in the mouth; it even has an anaesthetic-like smell. Propolis has traditionally been used to reduce pain externally in wounds, burns and especially mouth ulcers. Awareness of this characteristic no doubt encouraged researchers to explore its use as an anaesthetic.
In 1957 the Russian researcher, Prokopovich9 and others found that an alcoholic extract of propolis produced an anaesthetic effect on rabbit cornea that they believed to be stronger than that of cocaine or procaine. Similar experiments were repeated at the Veterinary Institute of Bulgaria by Tsakov10 in 1973. These conﬁrmed a similar anaesthetic effect using ethanolic and aqueous extracts of propolis but much weaker—30 per cent weaker than 50 per cent novocaine— than that claimed by the Russians. Two years later the same researcher11 found that a 30 per cent ethanolic extract of propolis introduced orally produced a good anaesthetic reaction in dogs and sheep within 15–20 minutes. Tsakov claims he ‘saw no difference between the anaesthetic effect and that of novocaine.’
In 1979 German researchers12 found that ethanolic extracts of propolis and, in particular, of some of the ﬂavonoids in propolis, notably pinocembrin, pinostrobin and caffeic acid esters each produced local anaesthetic effects on rabbit and mouse cornea. The three ﬂavonoids, when applied alone, were found to be nearly three times as potent as the total extract. In particular, the local anaesthetic activity of pinocembrin or caffeic acid ester mixture was about one tenth of that of lidocaine.
In our earlier discussion on the role of bioﬂavonoids, Havsteen showed how bioﬂavonoids operate to block an allergic reaction caused by the release of histamine and serotonin from the master cells once allergens have attached themselves. They do this by inhibiting the operation of the acids which break into the cells. However, the only known side effect of any consequence experienced by propolis users is that of allergic response. This usually manifests itself as a mild rash on contact with propolis and affects about one in 1000.
Russian researchers in 1973 noted that an ethyl alcohol extract of propolis was able to reduce the acid content in pork fat.
The antibiotic properties of propolis are perhaps best known and most widely researched. Sixty-seven research papers in this area alone were published between 1973 and 1994.15 But research into the anti-microbial properties of propolis began even earlier, back in
1947 at the Kazan Veterinary Institute in the USSR. Russian work dominates the early research, illustrating why propolis came to be known as ‘Russian penicillin’. What follows is a chronological cross-section of the research exploring this important property.
At the 1958 International Beekeeping Congress, Feuereisl and others16 reported on the effectiveness of propolis against the tuberculosis bacilli (Mycobacterium). Tuberculosis was a serious problem in the USSR earlier in the century. Many thought it to be one of the diseases banished by modern antibiotic drugs. The re-emergence of tuberculosis worldwide, including in the UK, has revealed a strain untreatable by virtually all known antibiotics. It may be that propolis has a role to play here.
In 1960 French researchers demonstrated the bacteriostatic effect of propolis on Bacillus subtilis, Proteus vulgaris and Bacillus alvei. The effect was less marked for Salmonella and E.coli. Still in France, at the Institute Pasteur in 1964,18 the ﬂavonoids galangin and pinocembrin were identiﬁed as having the strongest anti bacterial effects.
In 1973 two Russians at the Kazan Veterinary Institute published a remarkable piece of work. In earlier research, Kivalkina had illustrated the anti-microbial properties of propolis and now wanted to ﬁnd out what effect the addition of propolis would have on the effectiveness of antibiotics against Staphylococcus aureus and E.coli. The results were startling. Propolis increased the bacteriostatic activity of three antibiotics, tetracycline, neomycin and polymyxin, against Staphylococcus aureus by between ten and
100 times. The effectiveness of a further range of antibiotics including penicillin against E.coli was similarly improved. They then tested the effectiveness of two antibiotic ointments when propolis was added. With propolis the ointments’ bacteriostatic action commenced within 15–30 minutes whereas without propolis bacteriostatic activity took between two and 12 hours to engage. This is an area that must be worth further investigation. There is a clear potential here for both reducing the dosage of traditional antibiotics and perhaps reducing the side effects of antibiotics.
Polish scientists in 197720 found that the anti-bacterial effect of propolis against Staphylococcus aureus was only present when propolis was delivered in the whole product rather than via speciﬁc ‘active’ elements, i.e. particular ﬂavonoids. In later research they found that propolis was active against only some of the Staphylo- coccus strains when isolated from pathological material. Norwegian research in 197721 found that propolis was not as effective against gram-positive bacteria like Listeria monocytogenes.
In a comprehensive study carried out in West Germany in 197922 propolis was compared to a range of conventional antibiotics. Propolis showed good results against some organisms but was less effective than traditional antibiotics against Bacillus subtilis, Staphylococcus aureus and Candida albicans.
Research was commissioned by the Russian Ministry of Health (Drugs Standards Control) in 198123 to test propolis against 106 different strains of Staphylococcus aureus. Strains resistant to some antibiotics were found to be sensitive to propolis and propolis was found to have a synergistic effect with all the antibiotics used.
Yugoslavian research conducted in 198524 tested 38 samples of propolis collected from all over the former Yugoslavia. Where high concentrations of the ﬂavonoid pinocembrin were found, and less so with galangin, the greatest activity against Bacillus subtilis was demonstrated.
In 1986 Polish researchers25 tested a mixture of 10 per cent ethanolic extract of propolis and 13 typical antibiotics against Staphylococcus aureus isolated from abscesses showing resistance to antibiotics. A compound effect was shown in 69 per cent whilst 11 per cent showed a synergistic effect.
In the same year, across the border in Czechoslovakia, researchers were demonstrating how propolis appeared to inhibit the syntheses of proteins by bacteria, suggesting that this may account for its anti-microbial action. We are reminded here of Dr Bent Havsteen’s research in Germany which showed how ﬂavonoids prevent the breakdown of the protein coating of viruses by inhibiting enzymatic action thus preventing them leaking into, and ‘infecting’ the organism.
1987 saw American researcher Lindenfelser show that propolis was active against 25 of 39 bacterial species.
Professor Scheller,28 of the Silesian School of Medicine in Poland, has explored many aspects of propolis. In 1988 he found that an ethanolic extract of propolis (EEP) was capable of increasing the number of plaque-forming cells in the spleen cells of immunised male mice, demonstrating their ability to produce anti-bodies. The effect of the propolis was three times greater than in the controls. This effect increased if the dose was repeated and if the dose was increased.
In 1989, Cora Rosenthal,29 an Israeli researcher, found whilst an aqueous extract of propolis had no anti-microbial effect, an ethanolic extract had an inhibitory effect on a range of bacteria including Staphylococcus aureus.
In 1990 Grange and Davey at the National Heart and Lung Institute, London30 published what has turned out to be a landmark piece of research for propolis in the West. They found that in dilutions of 1:20, propolis completely inhibited the growth of Staphylococcus aureus including the MRSA [Methicillin Resistant Staphylococcus Aureus] strains. It partially inhibited growth of others but had no effect on still other strains. This research was important for two reasons. Firstly, it ﬁnally gave some credibility in the West to the work which had been going on in Eastern Europe for decades. Secondly, by demonstrating that propolis could inhibit MRSA it showed that propolis may have a role in helping to solve a serious and urgent problem in UK hospitals. In 1990 perhaps 50 per cent of UK hospitals were infected with MRSA. Today it is nearer 70 per cent and we still have no solution.
Back in Russia, in 1991, researchers found that propolis was effective against a further range of bacteria—Staphylococcus viridians and S. pyogenes, Diplococcus pneumonia and the gram- negative organisms E.coli, Salmonella spp. and Shigella ﬂexneri.
Research at the University of Ferrara, in Italy, tested a range of commercial extracts of propolis for their anti-microbial and antifungal properties. The research showed that 30 per cent extracts of propolis in oil, ethanol, propylene glycol and glycerine had differing anti-microbial effects. The extracts prepared in glycerine inhibited microbial development for only a few days, whereas the other preparations maintained an inhibition for up to two weeks.
In 1996 I commissioned research at the University of Oxford. Using a commercially available alcohol propolis tincture. Dr Philip Calder and others33 (including O. K. Mirzoeva, from the University of Moscow) explored its effect on the growth and motility of bacteria. They found that propolis was effective against gram- positive and some gram-negative bacteria. More interestingly, they found that some of the components of propolis—cinnammic acids and ﬂavonoids in particular—had the effect of ‘uncoupling’ the energy ﬁeld of the bacteria, inhibiting their ability to move around. They believed that this change in the bioenergetic status of the bacteria could be responsible for the anti-microbial action as well as for the way propolis works synergistically with antibiotics.
The 25 research projects listed above span a period of 40 years. Western interest has appeared in the last ten years with ﬁve out of the seven most recent studies coming from the West. Whilst some new developments have emerged from this work, in the main they conﬁrm the ﬁndings of earlier Eastern European studies. Inevitably, results from these studies are not always consistent. Some studies emphasise the importance of the type of extract used and the amount used, others the area from which it is collected or the season in which it is collected. What we must continually bear in mind is the absence of any single standard material. Grange, in his paper, refers to propolis as an unstable substance. Perhaps complex and unpredictable would be a more appropriate description. Certainly it is impossible to truly compare research ﬁndings unless we are ﬁrst and foremost clear about what material we are comparing.
Fungal problems have grown exponentially over the last ten years. Treatment with chemical drugs is increasingly difﬁcult. The same thing has happened with anti-fungal drugs as happened with anti biotics—the fungi have learnt to adapt to and resist increasingly sophisticated and stronger chemical drugs. The new drugs are themselves now causing complex adverse reactions in the body, particularly in relation to our immune response mechanisms.
In 1973 Czechoslovak researchers34 found that propolis was as effective against 12 micro-organisms as 12 units of penicillium or 25 units of fungicidin. Again, Czech researchers in 197535 showed that an ethanolic extract of propolis inhibited the growth of 60 strains of yeast tested. One year later, the same researchers36 found that propolis had a similarly inhibitory effect on 38 strains of fungi including Candida albicans as well as those fungal organisms responsible for ringworm and tinea.
In 1977 Polish researchers37 found that an ethanolic extract of propolis was lethal against the protozoa Trichomonas vaginalis and Toxoplasma gondii. This research supports research illustrating the effectiveness of propolis in treating purulent vaginal infections.
In 1979 researchers in the Federal German Republic38 found that the ﬂavonoid pinocembrin, present in propolis, was particularly effective against fungal infections externally, but it was not effective when injected into infected mice. Too much of the pinocembrin was excreted, leaving insufﬁcient in the blood serum to destroy the fungi.
Research at the University of Zagreb39 in 1982 showed that high concentrations of propolis inhibited the growth of the respiratory tract fungus Aspergillus sulphureus and reduced the toxins produced by it for up to ten days.
Polish researchers as the Institute of Medicinal Plants in 1987 tested the effect of a mixture of 10 per cent EEP and ten anti-fungal preparations on nine strains of Candida albicans isolated from human skin or the mucous membrane. They found that propolis improved the effectiveness of all the preparations but worked most effectively when combined with natamycin and ﬂucytosine.
In 1987 Cuban researchers tested aqueous and alcoholic extracts of propolis against two strains of Candida albicans. The aqueous extract had no effect and the alcoholic extract had only a weak effect. French research in the same year42 compared the effectiveness of propolis with nine anti-fungal drugs on four fungi that cause infections in humans. Propolis was as effective or more effective than most of the other preparations against three of the fungi. The most effective results were achieved against Scopulariopsis brevicaulis using a combination of propolis with propylene glycol. Propylene glycol appeared to enhance the effectiveness of propolis all round.
Finally, in 1989 Czech researchers tested a 10 per cent ethanolic extract of propolis against 17 fungal pathogens. Propolis was found to be active against them all. Of seven components of propolis separately tested, benzoic acid, salicyclic acid and vanillin were identiﬁed as strongly fungistatic.
The inﬂammatory response occurs when cell membranes are ruptured and fatty acids are produced, which in turn produce arachidonic acid, triggering the creation of prostaglandins and leukotrienes. The prostaglandins and leukotrienes cause leakage from blood capillaries—reddening of skin tissue, release of histamine, pain and a collection of ﬂuid in the area.
Ruptured cell membranes
LEAD TO Release of fatty acids LEAD TO
Production of arachidonic acid
Production of prostaglandins and leukotrienes
WHICH CAUSE Leakage from blood capillaries Reddening of the skin
Release of histamine
Pain and collection of ﬂuid
Diagram 1: The inﬂamatory process
The inﬂammatory process is a key factor in a variety of debilitating diseases including asthma, psoriasis, adult respiratory distress syndrome, allergic rhinitis, gout, rheumatoid arthritis, migraines, inﬂammatory bowel disease, gingivitis and mouth ulceration.
In a study of propolis consumers carried out in 1995 nearly 70 per cent were using it to treat health problems caused by inﬂammation. Thirty-nine per cent used it for arthritis, rheumatism and muscular pain, 18 per cent used it for asthma and bronchitis, and ten per cent used it for skin problems like eczema and psoriasis.
We have already examined Dr Bent Havsteen’s research at the University of Keil in 1978. In that work he showed how he believed that ﬂavonoids blocked the enzymes seeking to rupture the cell membrane thus, preventing the inﬂammatory process from starting.
In 1979 a Romanian patent was registered for a product containing propolis and described as having anti-inﬂammatory and antiseptic properties. The product was to be delivered as a gel for application to inﬂamed mucosal conditions. Researchers in Romania in 198446 induced rheumatic fever in rats and then fed them propolis extract daily. The treatment led to a remission of the symptoms of the fever including a softening of the cartilage around the joints and a reduction of lesions.
Hungarian researchers reporting to the International Congress of Apiculture in Japan in 198647 showed how certain fractions and isolated compounds of propolis and a commercially available product reduced inﬂammation when fed to rats with induced inﬂammatory conditions.
In 1996 a unique collaborative research venture between the Silesian Medical School, the National Institute of Health in Japan and the Hebrew University, Jerusalem,48 reported its ﬁndings. Various isolated phenolic components of propolis were tested for their degree of anti-inﬂammatory activity. CAPE (caffeic acid phenylethyl ester) was found to be 100 per cent effective using the method chosen whilst the three ﬂavonoids (galangin, kaempferol and kaempferid) were 73–93 per cent effective.
In the same year research commissioned by the author took place at the University of Oxford. Propolis and various components of propolis, notably CAPE, were tested for their anti inﬂammatory effect on acute peritoneal inﬂammation in vivo (mice). Dietary propolis signiﬁcantly suppressed the creation of arachidonic acid which leads on to creation of prostaglandins. However, CAPE was most effective in blocking the development of prostaglandins.
The last two pieces of research provide powerful evidence of the ability of propolis, and in particular of certain components of propolis, to inhibit the inﬂammatory process. Problems in the West with anti-inﬂammatory drugs reﬂect the nature and scale of prob lems with antibiotics and anti-fungal drugs. In particular, the tend ency of some commonly used drugs to cause serious damage to the stomach has caused alarm amongst users. The prospect of developing a natural alternative in this huge market has no doubt encouraged researchers.
Strictly speaking, the remarkable piece of research discussed below belongs to the above section. Radiation is a signiﬁcant stimulant for free radicals. In a nuclear age we are surrounded not only by the dangerous potential of nuclear power and nuclear weapons but also are continually over-exposed to low-level radiation through X-rays and other forms.
In 198950 researchers at Silesian School of Medicine in Poland,
and the University of Southern California, collaborated in a project designed to test the extent to which propolis could protect mice exposed to gamma radiation. One group of mice was injected with a propolis preparation both before and after the gamma irradiation. The second group was not treated at all. The non-treated mice died within 12 weeks whereas the mice treated with propolis survived. In the surviving group the leucocyte count as well as their spleen plaque formation activity returned to normal. The authors suggest that an antioxidant and free radical scavenger in the propolis was responsible for the protective effect. Protection is greatest if the propolis is delivered prior to or shortly after the irradiation.
Antioxidant and preservative
The natural process of breakdown that goes on continually in the body leads to the production of so-called free radicals. These free oxygen molecules would, if not mopped up and balanced by the production of antioxidants, lead inevitably to the complete break down of the organism through cancer, heart disease, arthritis and a variety of other degenerative diseases. Stress, infections, X-rays, pollution and poor diet all contribute to the creation of free radicals. Interest in understanding and managing antioxidant activity has been very high over recent years. The review of research which follows looks at the role of propolis as a preservative as well as ways in which propolis can assist living organisms to maintain the free radical–antioxidant balance.
In 1976 researchers at the Russian National Bee Keeping Institute, Ryazan,51 found that an extract of propolis had more than twice the antioxidant activity of synthetic preservatives when applied to ground white ﬁsh stored in a refrigerator.
Similar research was conducted by the Egyptian Ministry of Agriculture in 1980.52 Five natural substances, including an ethanolic extract of propolis, were tested as antioxidants in frozen meat. The aqueous extract was found to have less effect than the ethanolic extract, which was found to have the greatest effect of all the compounds tested. Interestingly, bearing in mind the powerful taste and smell of propolis, the ﬂavour of the meat was unaffected.
In 1980 the Institute of Veterinary Medicine, Belgrade,53 tested
six different propolis extracts on fresh lard at 10°C (50°F). Propolis and all its extracts had strong antioxidant effects, though there were some differences between the extracts. Similar research was undertaken at the Department of Veterinary Medicine in Belgrade in 1981.54 The antioxidant/preservative properties of 0.1 per cent propolis solution were compared with chemical preservatives on pigs’ back fat and lard samples. The propolis products were found to be equally as effective as the synthetic products.
In 1982 Veterinary researchers in Belgrade55 again used propolis dissolved in 96 per cent ethanol to preserve anatomical specimens of muscle, liver, kidney and other tissues. After six months the samples were still in good condition.
Bulgarian researchers in 198456 chose to test the extent to which 1–5 per cent concentrations of propolis would prevent oxidation in lard (chosen as a model lipid system). They looked at both the effect of propolis as a whole and at the action of individual ﬂavonoids. They found that best results were achieved using the whole propolis extract and that individual ﬂavonoids were not as effective.
The commercial potential of using propolis as a preservative for food is recognised by two Japanese patents, one for a propolis product that can be applied to the food itself 57 and another where propolis is integrated into food packaging.
Russian researchers at the Alma Ata Medical Institute in 1986 found that propolis fed to mice with salmonella stabilised the lipid peroxidation caused by the disease. Propolis acted as an antioxidant and subsequent dissection showed that the extent of pathological changes usual in salmonella was much reduced. The researchers believed that propolis could provide a natural treatment for salmonella.
Two years later, in 1988, the same researchers compared propolis and vitamin E as natural antioxidants. Polyunsaturated fatty acids included in animal feed increased the rate of lipid peroxidation in the animals fed. Both vitamin E and propolis stabilised this process but the increase in body weight of the animals taking propolis indicated that propolis had a stronger antioxidant effect.
In 1990 the ﬁrst research in this area in the West was undertaken at the University of Southern California.61 Their ﬁndings linked the antioxidant properties in propolis to the high quantities of ﬂavonoids present in the extract. The propolis extract inhibited luminol H2O2 chemiluminescence in vitro.
Romanian research in 199162 showed that a puriﬁed water- soluble extract of propolis had an antioxidant effect on a range of chemical reactions which produce hydrogen peroxide.
Research at the Institute of Experimental Apiculture in Cuba in 1993 indicated that extracts of Cuban propolis had antioxidant properties and this could be attributed to their free radical scavenging activity against alkoxy radicals and, to a lesser degree, against superoxide.
Water-extracted propolis was compared with an ethanol extract in research at the University of Munich, 1993.64 The aqueous extract of propolis was found to exhibit a higher antioxidant property and inhibitory activity than the ethanolic extracts.
In 1997, Lithuanian researchers65 reported on their work to further test the antioxidant and pro-oxidant activity of propolis on blood lipoproteins. They found that propolis acted as an antioxidant at lower concentrations whilst at higher concentrations propolis became a pro-oxidant. Finally, work undertaken at the University of Moscow in 1994 showed how certain extracted compounds of propolis, notably CAPE, could block the formation of reactive oxygen species in human neutrophils.
Degenerative diseases are increasing. As we enter a new millennium four out of ten people are expected to suffer from cancer at some point in their lives and this ﬁgure is increasing. Environmental pollution and poor nutrition all make us more vulnerable. The fact that propolis operates as an antioxidant adds still greater value to it for maintaining positive health. Research illustrating the preservative properties of propolis may also begin to attract commercial interest as the public turns away from chemical and irradiation preservation systems.
The effect of propolis in the hive is often referred to as antiseptic although this probably oversimpliﬁes the effect. The most interesting research in this area was carried out in Italy in 1989. Panizzi67 prepared a solution of two per cent propolis and 0.4 per cent essential oils in propylene glycol. He then sprayed this solution in aerosol form into three enclosed public areas—a school hall, analytical laboratory and a library. This propolis spray was found to reduce the number of microorganisms in the air by 93 per cent. Further tests would need to be done but there would seem to be a potential here for use in hospitals, particularly as part of the ﬁght against the airborne transmission of antibiotic-resistant bacteria.
Earlier we saw anecdotal evidence of successful treatment of cancer with propolis. The pharmacological research available is modest but relatively recent. In 1988, at the Institute of Cancer Research, University of New York, USA, Grunberger68 and his colleagues looked at the effectiveness of CAPE in an extract isolated from Israeli propolis. CAPE showed cytostatic effects on all type of cells but showed particular sensitivity to human cells. This research has created excitement amongst cancer researchers because CAPE is an easily extractable and replicable compound based on propolis.
In the same year, in the Federal Republic of Germany, Konig69
and others reviewed the anti-cancer and antiviral properties of CAPE. They conﬁrmed the cytostatic activity of the compound and put forward an explanation of the mechanism for its activity.
In 1989 a joint University of California-Silesian School of Medicine study70 compared the effectiveness of EEP with the cancer drug bleomycin on mice infected with Erlich Carcinoma. It was found that the survival rate of the mice after 55 days was
50 per cent for the group treated with propolis and 44 per cent for those treated with bleomycin. The research concluded that ‘the anti-tumoral property of EEP in the tumoured animal model studies is signiﬁcant and lasting.’
In 1990, at the University of Cardiff, Peter Ross71 tested various
aqueous and alcoholic extracts of propolis against cancer cells and against various bacteria and fungi. All extracts were found to have limited in vitro cytotoxic and cytostatic effects against certain cancer cells. Propolis extracts also slowed down the development of tumours in cancer-infected mice.
Japanese research in 1992 at the National Institute of Health, Tokyo,72 found that extracts and fractions of Brazilian propolis had a limited cytotoxic effect on cancer cells, arresting tumour development at certain stages, but had little effect on human diploid cells.
Basic and others73 in Croatia reported their ﬁndings on the use of some propolis derivatives (CAPE) in the proceedings of the International Congress of Apiculture, 1997. The number of infected tumours in the lungs of infected mice were reduced both by preventative and curative therapy with CAPE but less so with caffeic acid only.
Much of this anti-cancer research has focused on an attempt to utilise a narrow range of components in propolis (CAPE). Under standably, this is an area where the world is looking for new life-saving drugs—drugs that make an immediate and dramatic difference. Again and again, however, we have observed that propolis is as much as a preventative as a pure treatment of disease. CAPE is perhaps the nearest candidate so far for a traditional licensed drug. It has a level of effectiveness and it can be synthesised. Unfortunately, its effect is not sufﬁciently dramatic to warrant the cost involved in converting it into a traditional licensed medicine.
Antiviral and immuno-stimulant effects
Viral diseases are the most difﬁcult to control as antibiotics are not effective against them and they show a remarkable ability to change and adapt to drugs used against them.
An early study carried out by Kivalkina74 in 1969 at the Kazan
Veterinary Institute, showed that propolis had immune stimulant properties in guinea pigs infected with inﬂuenza. In 1971, Dunya vin75 in the USSR, tested propolis and copper cobalt IKP separately in combination with a paratyphoid antigen by injection in bulls. The results showed that both propolis and copper cobalt activated production of antibodies and phagacytosis, improving immunogenesis.
In 1971 Shevchenko and others76 in the USSR, gave a ﬁve per
cent alcoholic extract of propolis solution intra-nasally or as an aerosol, to mice just two hours before they were infected with inﬂuenza. The propolis preparation completely inhibited inﬂuenza virus proliferation. Interestingly, the preparation had no effect when given to mice already infected.
In 1976 research at the Kazan Veterinary Institute using aqueous and alcoholic extracts of propolis found that propolis inhibited the multiplication of the virus responsible for Aujeszky’s disease, which causes paralysis in cattle, horses and pigs. Propolis was more effective with mild infections. Similar research the following year at the Institute78 tested live Aujeszky’s disease vaccine with and without propolis. Those treated with the vaccine increased their antibody formation by two–three times. The propolis treatment also enhanced production of plasmacytes in the lymphoidal tissue of the spleen and lymph nodes.
Romanian research in 198179 tested propolis on mice both before and after they had been infected with inﬂuenza. Unlike the earlier study, the mice fed propolis after infection lived longer than those treated prior to infection.
Another Romanian study in 198380 showed that rats fed with a mixture of standardized propolis extract and E.coli antigen showed a marked increase in the formation of antibodies compared with the group not fed on propolis.
In 1985 Konig and others81 in the German Federal Republic, examined the role of propolis and some of its derivatives against the avian herpes virus. They tested a variety of separate compounds in propolis, including a range of ﬂavonoids and cinnamic acid compounds. Several of the compounds related to caffeic acid produced antiviral activity, whilst several other separate cinnamic acid derivatives and ﬂavonoids did not. In 1986 the same researchers tested a variety of extracts from tropical and non tropical propolis samples against avian herpes and Aujeszky’s virus.82 All the samples of non-tropical propolis showed inhibition of several herpes and Aujeszky’s viruses. Several caffeolic compounds showed high antiviral activity. The results indicate that the mechanism of inhibition may be related to virus-speciﬁc nucleic acid or protein synthesis. Various fractions of propolis were found to have a pronounced stimulating effect on the cell-mediated immune response in mice. In an immunobiological test there was an increase in the number of antigen-reacting cells.
In 1988 Neychev, a Bulgarian researcher produced a water-soluble fraction of propolis—mainly phenol derivatives. This was found to have immunostimulant activity in mice infected with inﬂuenza type A. Mortality in the untreated mice was 100 per cent whereas in the treated mice it was 60 per cent for those treated orally, but only 40 per cent for those injected.
In 1988 Scheller and his colleagues at the Silesian Medical School, tested the effect of a propolis extract administered to mice prior to immunisation. He found that the number of plague-forming cells (cells producing antibodies) in the spleen increased to three times greater than in the controls. Researchers concluded that immunisation should be carried out within 48 hours of EEP injections.
Italian researchers in 1990 tested a range of speciﬁc ﬂavonoids on a range of viruses—herpes, adenocrona and rotavirus. Whilst quercetin showed some inhibitory effect, this was only at very high doses. The other ﬂavonoids showed only a poor inhibitory effect.85
However, research undertaken by Amoros at the Faculty of Pharmacy in Rennes, France, in 1992 contradicts the above ﬁndings. Propolis, as well as a range of speciﬁc ﬂavonoids and ﬂavones, was clearly shown to inhibit the development of a range of viruses including poliovirus and herpes simplex viruses. Flavonols were found to have a greater effect than ﬂavones in the following order of importance: galangin, kaempferol and quercetin. In addition to its effect on virus multiplication, propolis was also found to exert a viricidal action on the enveloped viruses HSV and VSV. The synergy demonstrated by all combinations could explain why propolis is more active than its individual compounds.
In 1992 Serkedjieva, a Bulgarian researcher, tested propolis and some of its fractions on cultures infected with the Hong Kong inﬂuenza virus. The greatest effect was achieved when the propolis was applied both before and after infection. In this test phenolic acid derivatives found in propolis also showed activity but no greater than that of whole propolis extract.