Propolis, is the generic name for the resinous substance that collected by bees from different plant sources -like poplar, birch, pine, alder, willow and palm or sometimes from wounds in several other plants. Bees than mix these resins with their own waxes and β-glucosidase to use in the defense by coating and strengthening the inside walls of the hive. It is also used to cover holes and cracks and to repair combs, avoid insect invasions by shortening the entrance and to reduce the microbial growth on the walls of the hive, preventing wind and water from entering as well as to help maintain hive’s inner temperature to optimal degree.
The chemical composition of propolis is quite complex. Nearly 300 different compounds have been identified in propolis samples of diverse origins. Among these compounds, flavonoids are main active propolis constituents that are responsible for a large part of its biological activities. Flavonoids in propolis are classified into flavones, flavonols, flavanones, flavanonols, chalcones, dihydrochalcones, isoflavones, isodihydroflavones, flavans, isoflavans and neoflavonoids. Total flavonoid content has often been used as an index for evaluating the quality of propolis. The flavonoid content of propolis with less than 11% is considered as low quality, whereas 11-17% and the higher percentages are referred as good quality and high quality, respectively. Propolis is composed of resin (flavonoidaglycones, phenolic acids and their esters), waxes (mixture of long-chain a polar compounds), essential oils, pollen and other substances. Minor constituents of propolis are pollen, and other substances such as vitamins, minerals, amino acids and fatty acids.
Over the last 30 years, the pharmacological and chemical properties of propolis became the aim of intensive studies (nearly 4000 papers in journals and 2884 patents in which nearly half of them owned by China, Japan and Russia). Since the end of the 20th century, the paradigm related to the chemistry of propolis has changed drastically. By the 1960s, it was known that propolis is chemically complex, but stable. But lately now it is known that the chemical composition of propolis varies considerably, depending on the honeybee species, botanical source and extraction method, which greatly influence its properties. The quality of the propolis also depends on the beekeeper’ experience and knowledge, storage conditions with also regarding to the transport from the production area, the collecting season, day and time of collecting, the method of collecting and the place of propolis in the hive. The effect of the propolis to the human health also can vary due to the patient’s age, gender, physiology and sometimes life style
Local eco-flora have a very strong effect on the chemical composition of propolis. In order to produce propolis, the bees use material from several parts of plants and in different stages of development. Hence, the complexity and the chemical variety of propolis are deeply related to the eco-flora of the geographical region, which the bees commonly visit. This caused classifying propolis into different “types” (in Brasil there are 14 types). The characteristic constituents in temperate region propolis are flavonoids without B-ring substituents, such as chrysin, galangin, pinocembrin, pinobanksin which gives the characteristic color. Caffeic acid phenethyl ester (CAPE) is a major constituent of temperate propolis with broad biological activities, including inhibition of nuclear factor κ-B; inhibition of cell proliferation; induction of cell cycle arrest and apoptosis. In tropical region propolis, especially Brazilian green propolis (CAS: 9009-62-5), the dominating chemical components are prenylated phenylpropanoids (e.g., artepillin C) and diterpenes. For propolis produced in the Pacific region, geranyl flavanones are the characteristic compounds which are also found in propolis from the African region. Some flavonoids such as luteolin is rich in propolis of Portugal and Solomon Islands whereas some neo-flavonoids such as cearonin is rich in propolis of Nepal which the bees collect from Dalbergia spp. Anatolian propolis have different chemical profile in different types. For example one type is rich in monoterpenes, sesquiterpenes and diterpenes which are generally collected from Ferula spp, Pinaceae spp and Cupressaceae spp by honeybees.
Propolis is classified as an opotherapeutic medicine due to its complex chemical composition of organic secretions from bees. It is difficult to use raw propolis as it is difficult to remove from the human skin, it is hard, brittle with poor solubility and low oral bioavailability. Ethanol is the most frequently used solvent to extract, because it possesses more extraction capacity, removing around 50-60% of the propolis components, while the aqueous extraction method removes only around 10%. On the other hand many commercial ethanol extracted propolis preparations contain high level of alcohol which may cause nausea when taken with metronidazole, it can cause oral mucosal ulcerations, it is also dangerous to use these extracts for kids under 7 which may cause gastrointestinal health problems when they grow up. These extracts therefore cannot be (and should not) used for nose and throat.
Brazil is well known for its green propolis, produced by honeybees, which derives its resins mainly from the native shrub Baccharis dracunculifolia. However, due to the great biodiversity of Brazil, propolis from different geographic regions can vary profoundly in composition and 14 different types of propolis are found in Brazil, including the less common red propolis which can also found in Cuba, Bolivia, Venezuela, and México. Propolis of different geographic regions and their principal plants’ sources of chemical compounds in Anatolia is completely different and shows a great variation.