Isoflavones, antimicrobial activity

Secondary compounds known for their antimicrobial activity include many phenolics (e.g., flavonoids, isoflavones, and simple phenolics), glu-cosinolates, nonproteinogenic amino acids, cyanogenic glycosides, acids, aldehydes, saponins, triterpenes, mono- and disesquiterpenes, and last but not least, alkaloids (4,17,42,149,312). 

A number of isoflavones exhibit, in addition to oestrogenic activity, antimicrobial activity and other toxic effects. Examples of isoflavones exhibiting antimicrobial properties are prenylated isoflavones of legumes listed in Section 10.3.3.5.1, which occur mainly on the surface of leaves and other aboveground plant parts. Examples of such compounds are wighteon and luteon, which occur in lupines Lupinus spp.) together with other related compounds. 

Recently, it has been demonstrated that medicinal plants contain MDR pump inhibitors that actually enhance the activity of their own natural antimicrobial compounds. Plant amphipathic cations, such as berberine, have been shown to be good MDR substrates. Recent research has shown that in addition to berberine, Berberis species produce 5 -methoxyhydnocarpin-D, Fig. 10, an MDR inhibitor that enhances the action of this compound. In addition, isoflavones isolated Ifom Lupinus argenteus were found to enhance the antibacterial activity of a-linolenic acid, also found in the same plant [99]. 

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