Phytochemical investigation of the methanolic extract of Cucumis melo L. (Cucurbitaceae) seeds furnished a new triterpene benzoate derivative: cucumol B (1) and four known flavonoids: quercetin-3-O-β-D-glucopyranosyl-(1→6)-α-L-rhamnopyranoside (2), quercetin-3-O-β-D-glucopyranoside (3), quercetin (4), and luteolin (5). Their structures were identified by UV, IR, 1D (13C and 1H), 2D (HSQC, 1H-1H COSY, HMBC, and NOESY) NMR, and HRESIMS spectral as well as comparing with literature data. Compound 1 has been assessed for the in vitro cytotoxic effect against SKOV-3, MCF-7, and HCT-116 cell lines. It had selective and potent effect toward SKOV-3 and MCF-7 cell lines with IC50s 2.05 and 0.41 μM, respectively, in comparison to doxorubicin (IC50s 0.32 and 0.05 μM). However, it showed moderate activity toward HCT-116 cell line with IC50 8.27 μM.
Keywords: Cucumis melo; Cucurbitaceae; cucumol B; cytotoxic; triterpene.