Millexatins A-M, antibacterial flavonoids from Millettia extensa

The genus Millettia belongs to the family Leguminoseae, which are distributed in the tropical and subtropical regions of Asia, Africa and Australia. Some species of Millettia have been utilized as traditional medicines to treat various diseases. This genus is well known to produce flavonoids, chalcones, rotenoids and isoflavonoids and some of these compounds showed interesting biological activities such as cytotoxic, antimalarial, and antiinflamatory activities. Millettia extensa (Benth.) Baker is a large climbing shrub that is distributed in the north of Thailand. According to no phytochemical investigation or biological evaluation of this plant has been reported and its crude acetone extract showed good antibacterial activities. The first phytochemical investigation of Millettia extensa (leaf, root, and stem extracts) resulted in the isolation and identification of 13 new isoflavones, millexatins A-M, together with 19 known compounds. The structures of these new compounds were determined on the basis of their spectroscopic data. Most of the isolated compounds were evaluated for their antibacterial activities. Some compounds showed good antibacterial activity against the Gram-positive bacteria, Bacillus subtilis TISTR 008, Staphylococcus aureus TISTR 1466 and S. epidermidis ATCC 12228, with MIC values ranging from 2-8 μg/mL.

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