Leaf and Flower Extracts of Six Michelia L.: Polyphenolic Composition, Antioxidant, Antibacterial Activities and in Vitro Inhibition of α-Amylase and α-Glucosidase

Methanolic extracts of the leaf and flower of Michelia L., an evergreen aromatic genus widely used in landscaping, industry and medicine of various countries, were analyzed. The UPLC-ESI-MS/MS analysis led to the identification of 28 polyphenols from six Michelia species that widely distributed and cultivated in southern China, among which quinic acid and chlorogenic acid were the main components. The flower extract of Michelia maudiae had the most abundant polyphenols content, as well as high contents of total phenolic (117.31±7.26 mg GAE/g DW) and total flavonoid (251.60±15.56 mg CE/g DW). Meanwhile, it also showed outstanding performance in three antioxidant indexes of DPPH, ABTS and FRAP. The leaf extracts of Michelia chapensis and Michelia floribunda exhibited excellent inhibition against four pathogenic bacteria. Moreover, certain inhibitory activities were displayed by Michelia macclurei extracts against α-amylase and α-glucosidase. This study explored the biological activities of six Michelia species, and provided reference for variety selection with the aim of designing novel phyto-pharmaceuticals.