Sterols and Triterpenes from Growing in Saudi Arabia and Their Cytotoxic Activity.

A new lupane caffeoyl ester, lup-20(29)-ene 3β-caffeate-30-al (), and a new oleanane-type triterpene, 3-hydroxyolean-13(18)-en-12-one (), were isolated from the aerial parts of (Forssk), along with ten known triterpenes, including seven lupane-type lupeol (), 30-nor-lup-3-ol-20-one (), ∆-lupenone (), lup-20(29)-en-3,30-diol (), lupeol caffeate (), 30-hydroxy lup-20(29)-ene 3-caffeate (), and betunaldehyde (); three oleanane-type compounds were also identified, comprising -amyrone (), -amyrin (), and 11-oxo--amyrin (); together with six sterols, comprising -sitosterol (), stigmasterol (), 7-hydroxy--sitosterol (), 7-hydroxy-stigmasterol (), 7-keto--sitosterol (), and 7-keto-stigmasterol (). Their structures were elucidated using a variety of spectroscopic techniques, including 1D (H, C, and DEPT-135 C) and 2D (H-H COSY, H-C HSQC, and H-C HMBC) nuclear magnetic resonance (NMR) and accurate mass spectroscopy. Subsequently, the different plant extracts and some of the isolated compounds (, and ) were investigated for their possible cytotoxic activity in comparison to cisplatin against a wide array of aggressive cancer cell lines, such as colorectal cancer (HCT-116), hepatocellular carcinoma (HepG-2), and prostate cancer (PC-3) cell lines. Compound displayed broad cytotoxicity against all of the tested cell lines (IC ≅ 8 µg/mL in all cases), and a high safety margin against normal cells (IC = 70 µg/mL), suggesting that may be a highly selective and effective anticancer agent candidate. Notably, the evidence indicated that the mode of action of compound could possibly consist of the inhibition of phosphodiesterase I (80.2% enzyme inhibition observed at 2 µM compound concentration).