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Bioactive Sesquiterpenes and Lignans from the Fruits of Xanthium sibiricum

Shi, Yu-Sheng, Liu, Yun-Bao, Ma, Shuang-Gang, Li, Yong, Qu, Jing, Li, Li, Yuan, Shao-Peng, Hou, Qi, Li, Yu-Huan, Jiang, Jian-Dong, Yu, Shi-Shan
Journal of natural products 2015 v.78 no.7 pp. 1526-1535
Croton, Influenza A virus, X-ray diffraction, Xanthium, anti-inflammatory activity, circular dichroism spectroscopy, ears, edema, fruits, inhibitory concentration 50, lignans, mice, nuclear magnetic resonance spectroscopy, oils, sesquiterpenoids, spectral analysis
Seven new sesquiterpenes (1, 3–8), a new sesquiterpene natural product (2), and two new lignans (9 and 10), together with 15 known compounds, were isolated from the fruits of Xanthium sibiricum. The structures of the new compounds were established by NMR spectroscopic analysis, ECD calculations, and Mo₂(OAc)₄-induced circular dichroism, with the structures of 1 and 4 confirmed by single-crystal X-ray diffraction. Compound 1 is the first example of a 3/5/6/5 tetracyclic eudesmane sesquiterpene lactone formed at C-6 and C-7. In turn, compound 4 is the first example of a natural xanthane tetranorsesquiterpene, while compounds 5–8 are the first xanthane trinorsesquiterpenes found to date. Compounds 8, 11–15, 17, and 24 exhibited indirect anti-inflammatory activity by suppressing the lipopolysaccharide-induced proinflammatory factors in BV2 microglial cells, with IC₅₀ values between 1.6 and 8.5 μM. Furthermore, compounds 13 and 17 exhibited anti-inflammatory activity against ear edema in mice produced by croton oil, with inhibition rates of 46.9% and 37.7%, respectively. Compounds 8, 11, 12, 23, and 24 exhibited potent activity against influenza A virus (A/FM/1/47, H1N1) with IC₅₀ values between 3.7 and 8.4 μM.