Polyphenols and antimicrobial activity in extracts of Lippia alba (Mill.)

Total polyphenols content was evaluated in ethanolic and aqueous extracts of leaves and inflorescences of Lippia alba (Mill.), from plants cultivated in the Chaco province, northeastern of Argentina. The extracts were obtained by percolation, infusion and decoction. Total phenols content was determined by Folin Ciocalteu reagent, flavonoids content was determined in Al-complex form and the free radical scavenging activity was determined by DPPH radical. The antimicrobial screening was carried out by bioautography and in the active extracts the minimal inhibitory concentration and minimal bactericidal concentration was determined by the disc diffusion method. Results in terms of phenols content, flavonoids content and DPPH radical scavenging were higher in ethanolic extracts than in the aqueous ones. There were differences statistically significant in phenols and flavonoids contents of the extracts obtained with extraction solvents of different polarity. The aqueous extracts obtained by infusion presented smaller phenols content, higher flavonoids content and better free radical scavenging activity in comparison with the extracts obtained by decoction. Only ethanolic extracts presented antimicrobial activity and they were more active against Gram-positive bacteria.