Identification of antioxidant and antimicrobial compounds of Lippia species by bioautography.

The methanolic extracts of the leaves of Lippia species (L. pseudo-thea, L. hermannioides, L. alba, L. rubella, and L. sidoides) were tested for their antibacterial, antifungal, and antioxidant activity. Cytotoxicity was determined by using brine shrimp lethality bioassay. Phytochemical screening was also performed. The extracts showed a minimum inhibitory concentration (MIC) ranging from 78 to 5000 μg/mL for antibacterial activity against at least 2 species of bacteria, although none was active against Escherichia coli. Antifungal activity was found only for L. pseudo-thea (MIC, 625 μg/mL for Candida albicans) and L. sidoides (MIC, 625 μg/mL for both C. albicans and C. neoformans). The bioautography showed that flavonoids and coumarins are responsible for the antioxidant activity of the extracts and that the antimicrobial properties are due to flavonoids and terpenoids. The cytotoxic activity was stronger for L rubella extract. To our knowledge, this is the first report of the biological and chemical constituents of L. pseudo-thea, L. hermannioides, and L. rubella.