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New Antimycobacterial and Antimalarial 8,9-Secokaurane Diterpenes from Croton kongensis

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journal contribution
posted on 15.05.2003, 00:00 by Jirabhorn Thongtan, Prasat Kittakoop, Nijsiri Ruangrungsi, Janya Saenboonrueng, Yodhathai Thebtaranonth
Two new 8,9-secokaurane diterpenes, ent-8,9-seco-7α,11β-diacetoxykaura-8(14),16-dien-9,15-dione (1) and ent-8,9-seco-8,14-epoxy-7α-hydroxy-11β-acetoxy-16-kauren-9,15-dione (2), together with two known compounds, ent-8,9-seco-7α-hydroxy-11β-acetoxykaura-8(14),16-dien-9,15-dione (3) and ent-7β-hydroxy-15-oxokaur-16-en-18-yl acetate, were isolated from Croton kongensis. This is the first report on the presence of 8,9-secokauranes in the plant genus Croton. Diterpenes 13 exhibited antimycobacterial activity with minimum inhibitory concentrations (MICs) of 25.0, 6.25, and 6.25 μg/mL, respectively, and possessed antimalarial activity with IC50 ranges of 1.0−2.8 μg/mL. They also demonstrated comparable cytotoxicity toward the Vero (IC50 ranged from 0.9 to 3.2 μg/mL), KB (IC50 from 1.2 to 13.8 μg/mL), and BC cell lines (IC50 from 1.1 to 2.2 μg/mL, except for compound 1, which was inactive against BC cells).