Antibacterial and antioxidant flavonoid derivatives from the fruits of Metaplexis japonica.

Metaplexis japonica (Thunb.) Makino is widely distribution and cultivated as a vegetable in China. Chemical studies revealed that its stem and root are rich in polysaccharides, flavonoids, polyphenols, and steroids, which also exhibited interesting activities. However, little attention has been focused on the biological constituents in the fruits of M. japonica. In order to achieve the best use of M. japonica, a chemical investigation of the secondary metabolites of the fruits of M. japonica was performed, and led to the isolation of one new (1), along with eight known flavoniod derivatives (2-9). The antioxidant and antibacterial properties of the crude extract and compound 1 were deeply evaluated through antioxidant and antimicrobial assays. Among them, the crude extract showed significant antioxidant activities in all assays, as well as broad-spectrum antibacterial effects. These results suggested that crude extract of M. japonica would be a potential source as a possible preservatives for foods.