Bioactive compounds from Croton kongensis, Croton birmanicus and Millettia kangensis

Abstract

Chemical investigation of Croton kongensis, Croton birmanicus and Millettia kangensis, led to the isolation of four diterpenoids, seven flavonoids and an alkaloid. The structure determination of these compounds was accomplished by spectroscopic analyses (UV, IR, MS and NMR) and by comparison with previously reported data of known compounds. C. kongensis provided two new 8,9-secokauranes identified as ent-8,9-seco-7alpha,11beta-diacetoxykaura-8(14),16-dien-9,15-dione and ent-8,9-seco-8,14-epoxy-7alpha-hydroxy-11beta-acetoxy-16-kauren-9,15-dione, and also gave two known diterpenes, ent-8,9-seco-7alpha-hydroxy-11-acetoxykaura-8(14),16-dien-9,15-dione and ent-7beta-hydroxy-15-oxokaur-16-en-18-yl acetate. C. birmanicus was isolated to yield a known glutarimide alkaloid, julocrotine. Isolation of a crude extract of M. kangensis afforded two new furanoflavonoids identified as 3-methoxy-6-hydroxy-[4,5:8,7]-furanoflavone and 2,5,8-trimethoxy-[4,5:6,7]-furanoflava none, a new pyranoflavonoid, 3,6-dimethoxy-2-dimethyl-[5,6:8,7]-pyranoflavone, a new coumestan (4-hydroxy,5,6,7-trimethoxycoumestan), a new natural product (5,8-dimethoxy-[4,5:7,6]-furanoflavone), together with two known compounds, karanjin and 3,6-dimethoxy-[4,5:8,7]-furanoflavone. The isolated compounds were evaluated for their biological activities, including antimycobacterial, antimalarial, and cytotoxic activities. ent-8,9-Seco-7alpha,11beta-diacetoxykaura-8(14),16-dien-9,15-dione, ent-8,9-seco-8,14-epoxy-7alpha-hydroxy-11beta-acetoxy-16-kauren-9,15-dione, ent-8,9-seco-7alpha-hydroxy-11-acetoxykaura-8(14),16-dien-9,15-dione and ent-7beta-hydroxy-15-oxokaur-16-en-18-yl from C. kongensis exhibited antimycobacterial, antimalarial, and cytotoxicity activities, while julocrotine from C. birmanicus and 5,8-dimethoxy-[4,5:7,6]-furanoflavone from M. kangensis showed mild antimycobacterial activity.