Propolis is a bee product that is made when honey bees collect resinous material from the leaves and bark of plants. This resinous material is then subsequently mixed with beeswax and enzymes to produce propolis. Because the propolis is mainly of plant origin it is not surprising that it contains a large range of phytochemical compounds. Propolis is safe for consumption by humans and is composed of around 50 % wax and 50 % other components including essential oils, pollen, and a range of polyphenols that can account for as much as 58 % of the non-wax constituents of the propolis. If the extract is concentrated during manufacture, the final non-wax component of the propolis may contain up to 78 % polyphenols. Of the polyphenols in propolis, about 20 % are flavonoids, with other polyphenols present including a range of phenolic acids and lignins. Propolis also contains phenolic acids, phenolic aldehydes, phenols and their esters, ketophenols, coumarins, terpenes, vitamin, mineral, proteins, amino acids and sugars.
Evidence suggests that propolis may have beneficial effects against certain mood disorders. For example, in one study, the effects of propolis essential oil was investigated in mice. Mice were administered propolis essential oil and subsequently exposed to experimental stress. The propolis essential oil was effective at decreasing anxious behaviour in the mice, but did not appear to cause sedation in the mice. The researchers also observed a significant fall in the blood cortisol levels of the mice suggesting that the stress response was blunted. In addition, the levels of lipid peroxides fell significantly and at the same time levels of the antioxidant enzyme superoxide dismutase rose significantly in the blood of the mice. This suggests that a significant antioxidant effect was conferred by the propolis. Polyphenols have been shown previously to confer beneficial mood elevating and antioxidant effects on animals and humans, and so the high polyphenol content of the propolis may have been responsible for the effects seen in this study.
In another study researcher investigated the effects of an extract of propolis on the mood of rats exposed to experimental conditions designed to produce anxiety and depression in the rats. The results of the study showed that the propolis extract was able to significantly decrease both the anxious and depressive behaviour displayed by the rats. Further, the rats administered propolis extract had significantly improved antioxidant status compared to control rats. Propolis contains a number of phenolic acids and derivatives including a component called caffeic acid phenyl ester (CAPE). Researchers have investigated the effects of caffeic acid phenyl ester on the behaviour of mice exposed to experimental stress. The results showed that caffeic acid phenyl ester conferred a resistance to stress on the mice, and also decreased both anxious and depressive behaviour. In addition, the caffeic acid phenyl ester also attenuated changes to cellular signalling in neurones, that had occurred as a result of the elevated stress.
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