Steroidal saponins from Chlorophytum deistelianum

Plants of the genus Chlorophytum are known as a rich source of steroidal saponins[1 – 3] which have attracted the attention for their structural diversity and significant bioactivities such as cytotoxic, immunomodulating, antifungal, insecticidal activities, just to mention a few [4]. In our continuing search for bioactive saponins from the genus Chlorophytum[1 – 3] we investigated Chlorophytum deistelianum Engl. & Krause (= C. sparsiflorum Backer var. sparsiflorum) from a phytopharmacological point of view. C. deistelianum is a fleshy herb to 50 cm high, with white or greenish flowers. No study on the secondary metabolites of this plant has been reported so far. Therefore, we report herein the isolation of four previously undescribed steroidal saponins, called chlorodeistelianosides A – D (1-4) together with five known steroidal saponins from C. desteilianum. Their structures were determined by spectroscopic methods including 1D and 2D NMR experiments, ESI and HRESIMS. Compounds 1 and 2 are glycosides of hecogenin and its 24β-OH derivative, respectively, whereas 3 is a glycoside of (25R)-5α-22α-methoxyfurostane-2α,3β,26 triol and 4 a glycoside of (25R)-5α-furost-20(22)-en-12-one-3β,26 diol. Compounds 2 – 4 share the same sugar sequence at C-3 characterized as β-D-glucopyranosyl-(1→2)-[β-D-xylopyranosyl-(1→3)]-β-D-glucopyranosyl-(1→4)-β-D-galactopyranosyl whereas the sugar sequence of 1 was elucidated as β-D-glucopyranosyl-(1→3)-[α-L-rhamnopyranosyl-(1→4)]-β-D-xylopyranosyl-(1→3)-[β-D-glucopyranosyl-(1→2)]-β-D-glucopyranosyl-(1→4)-β-D-galactopyranosyl. Furthermore, seven compounds were examined for cytotoxicity against one human colorectal adenocarcinoma cell line (SW480) and one rat cardiomyoblast cell line (H9c2). Among them, three known spirostane-type glycosides exhibited cytotoxicity on both cell lines with IC₅₀ ranging from 8 to 10µM.

Keywords: Chlorophytum deistelianum, Asparagaceae, steroid saponins, NMR, cytotoxicity.

References:

[1] Acharya D, Mitaine-Offer A-C, Kaushik N, Miyamoto T, Paululat T, Lacaille-Dubois MA. Furostane-type steroidal saponins from the roots of Chlorophytum borivilianum. Helv Chim Acta 2008; 91: 2262 – 2269

[2] Acharya D, Mitaine-Offer A-C, Kaushik N, Miyamoto T, Paululat T, Mirjolet JF, Duchamp O, Lacaille-Dubois MA. Cytotoxic spirostane-type saponins from the roots of Chlorophytum borivilianum. J Nat Prod 2009; 72: 177 – 181

[3] Acharya D, Mitaine-Offer A-C, Kaushik N, Miyamoto T, Paululat T, Mirjolet JF, Duchamp O, Lacaille-Dubois MA. Steroidal saponins from Chlorophytum orchidastrum. J Nat Prod 2010; 73: 7 – 11.

[4] Lacaille-Dubois MA. Bioactive saponins with cancer related and immunomodulatory activity: recent developments. In: Atta-Ur-Rahman, editor. Studies in Natural Products Chemistry series. Amsterdam: Elsevier, 2005; 32: 209 – 246