Abstract
Propolis is the resinous material that bees gather from leaf buds, flowers and vegetables. Propolis extracts contain constituents with a broad spectra of pharmacological properties and are important ingredients of popular dietary supplements. Propolis extracts were evaluated in vitro for inhibition of recombinant human monoamine oxidase (MAO)-A and MAO-B. The dichloromethane extract of propolis showed potent inhibition of human MAO-A and MAO-B. Further fractionation identified the most active fractions as rich in flavonoids. Galangin and apigenin were identified as the principal MAO-inhibitory constituents. Inhibition of MAO-A by galangin was about 36 times more selective than MAO-B, while apigenin selectivity for MAO-A vs. MAO-B was about 1.7 fold. Apigenin inhibited MAO-B significantly more potently than galangin. Galangin and apigenin were further evaluated for kinetic characteristics and the mechanism for the enzymes’ inhibition. Binding of galangin and apigenin with MAO-A and -B was not time-dependent and was reversible, as suggested by enzyme-inhibitor binding and dissociation-dialysis assay. The inhibition kinetics studies suggested that galangin and apigenin inhibited MAO-A and -B by a competitive mechanism. Presence of prominent MAO inhibitory constituents in propolis products suggests their potential for eliciting pharmacological effects that might be useful in depression or other neurological disorders. The results may also have important implications in drug-dietary supplement interactions.
Highlights
Propolis is the resinous material that bees gather from leaf buds, flowers and certain vegetables [1]
We report the kinetic characteristics of inhibition of monoamine oxidase (MAO)-A and B by galangin and apigenin and the properties of their binding with the recombinant enzymes
The results presented in this paper demonstrate inhibition of MAO-A and MAO-B as an important pharmacological action of the propolis extracts
Summary
Propolis is the resinous material that bees gather from leaf buds, flowers and certain vegetables [1]. The bees gather this and transform it, in order to disinfect the beehive, seal cracks, build panels, as well as using it as an antimicrobial agent and disinfectant. Its alcoholic extract (called tincture) is well known and used for therapeutic purposes, principally for its stimulant action on the organism’s defense system. It is used as antioxidant and anti-microbial agent, stimulant, and for its burn healing and anti-inflammatory activity [3,4,5].
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