Walsura yunnanensis C. Y. Wu is endemic to the Xishuangbanna region of Yunnan Province, SW China. Earlier investigations have shown the presence of limonoids and phenolic compounds. In a continuing study of the medicinal plants of Xishuangbanna for biologically active secondary metabolites, researchers from Xishuangbanna Topical Botanical Garden (XTBG) investigated the leaves and twigs of W. yunnanensis.

The leaves and twigs of W. yunnanensis were extracted three times with 95% EtOH. After removing the solvent, the ethanol extracts were suspended in water and then partitioned successively with petroleum ether, EtOAc, and n-BuOH. The EtOAc-soluble fraction was purified by column chromatography to produce nine new cedrelone limonoids (1−9) and one new cycloartane triterpenoid (10).

The structures of the 10 compounds were elucidated on the basis of spectroscopic analysis and by comparison with literature data. Compounds 3 and 5 exhibited potent cytotoxicity against five human tumor cell lines with IC₅₀ values in the range 2.2-4.2 μM.

The researchers described the extraction, isolation, structure elucidation, and cytotoxicity evaluation of the 10 compounds in Journal of Natural Products, with a title of “Limonoids from the Leaves and Twigs of Walsura yunnanensis”.

The study was financially supported by CAS 135 program (XTBG-F02), NSFC-U1302222, and Ethnobotanical Investigation of Plants for Industrialization in Southwest China (SQ2012FY4910027).

Twigs and leaves of Walsura yunnanensis C. Y. Wu (left) and compounds isolated

(Image by JI Kailong)