Antitrypanosomal Cycloartane Glycosides from Astragalus baibutensis

• Published in: Chemistry & biodiversity 2006-08, Vol.3 (8), p.923-929
• Main Authors: Çalış, İhsan, Koyunoğlu, Semra, Yeşilada, Akgül, Brun, Reto, Rüedi, Peter, Taşdemir, Deniz
• Format: Article
• Language: English
• Subjects: Animals; Antiprotozoal Agents - chemistry; Antiprotozoal Agents - pharmacology; Astragalus baibutensis; Astragalus Plant - chemistry; Baibutoside; Cycloartane glycosides; Glycosides; Glycosides - chemistry; Glycosides - pharmacology; Magnetic Resonance Spectroscopy; Molecular Structure; Terpenes; Triterpenes - chemistry; Trypanosoma - drug effects; Trypanosoma brucei rhodesiense; Trypanosoma sp
• ISSN: 1612-1872; 1612-1880
• DOI: 10.1002/cbdv.200690094

Baibutoside (5), a new cycloartane‐type triterpene glycoside, has been isolated from the roots of Astragalus baibutensis along with four known glycosides, acetylastragaloside I (1), and astragalosides I, II, and IV (2–4, resp.). The structure elucidation of the compounds were achieved by a combination of one‐ and two‐dimensional NMR techniques (DQF‐COSY, HSQC, HMBC, and ROESY), and mass spectrometry (ESI‐MS), where all the compounds were shown to have cycloastragenol (=(20R,24S)‐3β,6α,16β,25‐tetrahydroxy‐20,24‐epoxy‐9,19‐cyclolanostane) as aglycone. All compounds were tested for in vitro antiprotozoal activity. Compounds 1–4 displayed notable activity vs. Trypanosoma brucei rhodesiense, with acetylastragaloside I (1) being the most potent (IC50 9.5 μg/ml). Acetylastragaloside I (1) was also lethal to T. cruzi (IC50 5.0 μg/ml), and it is the first cycloartane‐type triterpene with remarkable trypanocidal activity against both T. brucei rhodesiense and T. cruzi. However, it exhibits some cytotoxicity on mammalian cells.