A study of the chemical constituents of the stem bark of Vitellaria paradoxa (Sapotaceae) has resulted in the isolation and characterization of a new ursane-type triterpenoid, 2β,3β,19α-trihydroxyurs-12-en-28-oic acid (1), together with seven known compounds: betulinic acid (2), 1α,2β,3β,19α-tretrahydroxyurs-12-en-28-oic acid (3), β-sitosterol (7), sigmasterol (8), (-)-epicatechin (9), (+)-catechin (10) and quercetin (11). The structure of the novel, ursane-type acid 1 was elucidated on the basis of detailed spectroscopic analysis including IR, HRMS (ESI), 1D and 2D NMR and a comparison to previously described, related natural products. Preliminary cytotoxicity assays against the MDA-MB-231 breast cancer cell line indicated that betulinic acid 2 and its corresponding methyl ester 5 were the most active compounds tested with IC50 values of 19.9 μM (17.2–23.1 μM, 95% CI) and 32.9 μM (24.9–43.4 μM, 95% CI), respectively. Esterification of acids 1–3 afforded the corresponding methyl esters 4–6 for additional structure-activity relationship (SAR) analysis. In general, the activity against the MDA-MB-231 breast cancer cell line increased upon esterification of the triterpenoids screened.
plant-derived natural productsursane family isolation structure elucidation Apoptosis/necrosis assay
The authors would like to acknowledge the council for International Exchange of Scholars (CIES) for the J. William Fulbright Visiting Scholar program to Dr Kenneth Eyong. The Baylor CPRIT Synthesis and Drug Lead Discovery Laboratory (supported by the Cancer Prevention and Research Institute of Texas R1309 and Baylor University, College of Arts and Sciences) and the Molecular Bioscience Center hosted Dr. Eyong. The Departments of Chemistry & Biochemistry and Department of Biology at Baylor University are acknowledged for infrastructure and financial support. The University of Yaounde I and the Government of Cameroon are acknowledged for financial support through the Fonds d’Appuis a la Recherche.
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