Bees make propolis to seal cracks and repair other hive damage. Sealing cracks reduces the risk of disease and parasites entering the hive. The resinous nature of propolis also make it ideal for preventing putrefaction within the hive, e.g. small mice or lizards that might die in the hive can be sealed in in propolis.
Propolis varies between hives, districts and seasons. It is usually dark brown in color, but colour variations occur depending on available vegetation.
The environment also affects chemical composition. Propolis may contain 180 constituents - resins, balsams, waxes, essential oils, pollen and minerals. The main chemical classes present are flavonoids (e.g. Quercetin, Pinocembrin), phenolics (e.g. Caffeic acid) and various aromatic compounds.
The predominant constituents of propolis are complex natural chemical compounds called flavonoids. Their well-reported antibacterial, antiviral, anti-fungal, antioxidant and anti-inflammatory properties are believed to account for most of the biological activity of propolis.
Dried propolis is scraped from hives and frames. The flakes may then be powdered for use or soaked to extract desired constituents.