No abstract

No abstract

Structures of some bioactive phytochemicals in bran extract of the black rice cv. Riceberry that had demonstrated anti-cancer activity in leukemic cell line were investigated. After saponification with potassium hydroxide, separation of the unsaponified fraction by reversed-phase high performance liquid chromatography (HPLC) resulted in four sub-fractions that had a certain degree of anti-proliferation against a mouse leukemic cell line (WEHI-3 cell), this being IC50 at 24 h ranging between 2.80–467.11 μg/mL. Further purification of the bioactive substances contained in these four sub-fractions was performed by normal-phase HPLC. Structural characterization by gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance spectroscopy (NMR) resulted in, overall, the structures of seven phytosterols and four triterpenoids. Four phytosterols, 24-methylene-ergosta-5-en-3β-ol, 24-methylene-ergosta-7-en-3β-ol, fucosterol, and gramisterol, along with three triterpenoids, cycloeucalenol, lupenone, and lupeol, were found in the two sub-fractions that showed strong anti-leukemic cell proliferation (IC50 = 2.80 and 32.89 μg/mL). The other sterols and triterpenoids were campesterol, stigmasterol, β-sitosterol and 24-methylenecycloartanol. Together with the data from in vitro biological analysis, we suggest that gramisterol is a significant anti-cancer lead compound in Riceberry bran extract.

Rhinacanthin-M, -N and -Q, natural products isolated from the medicinal plant Rhinacanthus nasutus, and 39 novel naphthoquinone esters have been synthesized in excellent yield by esterification of naphthoquinone-3-(propan-3'-ols) with benzoic or naphthoic acids. Almost all the naphthoquinone esters that contain a C-3 hydroxy group showed significant cytotoxicities against KB, HeLa, and HepG2 cell lines. In contrast, ester derivatives lacking the C-3 hydroxy group were inactive to the cancer cell lines. Two methyl substituents on the C-2' of propyl chain conferred more potent cytotoxicity than when there is only one or no methyl group. Naphthoate esters exhibited greater cytotoxicity than benzoate esters. Computer modeling has been done to obtain a first look at the mode of action in connection with these observations.