Novel acylated steroidal glycosides from Caralluma tuberculata induce caspase-dependent apoptosis in cancer cells

Waheed, Abdul, Barker, James, Barton, Stephen J., Khan, Gul-Majid, Najm-Us-Saqib, Qazi, Hussain, Manzoor, Ahmed, Sabbir, Owen, Caroline and Carew, Mark A. (2011) Novel acylated steroidal glycosides from Caralluma tuberculata induce caspase-dependent apoptosis in cancer cells. Journal of Ethnopharmacology, 137(3), pp. 1189-1196. ISSN (print) 0378-8741

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Abstract

AIM OF THE STUDY: Pregnane glycosides are potent cytotoxic agents which may represent new leads in the development of anti-tumour drugs, particularly in the treatment of breast cancer, because of the structural similarity to estrogenic agonists. Caralluma species are natural sources of a wide variety of pregnane glycosides. The aim of the study was to isolate, using an activity-guided fractionation approach, novel pregnane glycosides for testing on breast cancer and other tumour lines. MATERIALS AND METHODS: The effect of crude extracts, specific organic fractions and isolated compounds from Caralluma tuberculata was tested on the growth and viability of MCF-7 estrogen-dependent, and MDA-MB-468 estrogen-independent breast cancer cells, Caco-2 human colonic cells, HUVECs and U937 cells. Neutral red uptake and MTT assays were used. Apoptosis was detected by Western blot of poly-(ADP ribose) polymerase (PARP) as were other markers of nuclear fragmentation (DNA ladder assay, staining of cells with nuclear dye DAPI). The involvement of caspases was investigated using the pan-caspase inhibitor Z-VAD-FMK. RESULTS: The ethyl acetate fraction of Caralluma tuberculata was found to be the most potent anti-proliferative fraction against all three cancer cell lines. Two novel steroidal glycosides were isolated from the active fraction after a series of chromatographic experiments. The structure of the isolated compounds was elucidated solely based on 2D-NMR (HMBC, HETCOR, DQF-COSY) and MS spectral analysis as compound 1: 12-O-benzoyl-20-O-acetyl-3β,12β,14β,20β-tetrahydroxy-pregnan-3-ylO-β-D-glucopyranosyl-(1→4)-β-d-glucopyranosyl-(1→4)-3-methoxy-β-d-ribopyranoside, and as compound 2: 7-O-acetyl-12-O-benzoyl-3β,7β,12β,14β-tetrahydroxy-17β-(3-methylbutyl-O-acetyl-1-yl)-androstan-3-ylO-β-d-glucopyranosyl-(1→4)-6-deoxy-β-d-allopyranosyl-(1→4)-β-d-cymaropyranosyl-(1→4)-β-d-cymapyranosyl-(1→4)-β-d-cymaropyranoside. Compound 1 (pregnane glycoside) and compound 2 (androstan glycoside) induced apoptosis at <25μM after 48h as assessed by cell shrinkage, PARP cleavage, DNA fragmentation, and reversal with the caspase inhibitor. CONCLUSIONS: Two novel steroid glycosides isolated from Caralluma tuberculata possess moderate, micromolar cytotoxic activity on breast cancer and other cells in vitro, which may indicate a source of activity in vivo of interest to future drug design.

Item Type: Article
Additional Information: NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Ethnopharmacology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Ethnopharmacology, [VOL137, ISSUE 3, (2011)] DOI http://dx.doi.org/10.1016/j.jep.2011.07.049
Research Area: Cancer studies
Faculty, School or Research Centre: Faculty of Science, Engineering and Computing > School of Pharmacy and Chemistry
Depositing User: Mark Carew
Date Deposited: 08 Mar 2012 14:14
Last Modified: 26 Nov 2012 17:25
URI: http://eprints.kingston.ac.uk/id/eprint/21284

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