Antimicrobial activity of extracts from leaves of Michelia maudiae Dunn, Michelia chapensis Dandy and Michelia platypetala Hand was studied in the paper. The stability of extracts was detected. The extracting technology of active substances was optimized. At the same time, components of antimicrobial activity substances were determined preliminarily. The correlation between total phenols ratio and antimicrobial activity from leaves of three species of Michelia Linn. at different stages was studied. T...