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This study was carried out to investigate the protective effect of standardized γ-oryzanol-rich extracts on oxidative DNA damage induced by Fenton reaction and antiproliferative activity against human cancer cells. Six cultivars of Thai purple rice were collected in northern Thailand. Rice bran was extracted with hexane/ethyl acetate mixture and the extract was evaporated to obtain crude rice bran oil. Each rice bran oil was further purified by column chromatography to obtain the γ-oryzanol-rich extract. The extracts contained γ-oryzanol in the range of 1.17 -7.54 % w/w, in which GAM THOR exhibited the highest γ-oryzanol content. The extr \acts containing more than 5.0 % w/w γ-oryzanol (GAM THOR, GAM DOI MUSUR and GAM SUKHOTHAI-2) were selected to be standardized with γ-oryzanol and then the protective effect on oxidative DNA damage and antiproliferative activity against four human cancer cell lines (HT-29, HCT 116, MDA-MB-468 and PC3) were investigated. The extracts (10 µg/ml) exhibited a protective effect on oxidative DNA damage induced by Fenton reaction as compared with standard quercetin (lower than 5 µg/ml). Furthermore, all of the extracts exerted antiproliferative activity against human cancer cell lines in a dose-dependent manner. GAM THOR exhibited the highest antiproliferative activity against HT-29, HCT 116, MDA-MB-468 and PC3 with an 50% inhibition concentration value of 52.18 ± 1.21, 40.58 ± 5.69, 48.59 ± 2.40 and 51.61 ± 1.30 µg/ml, respectively. From these findings, γ-oryzanolrich extracts from Thai purple rice bran show potential as chemopreventive supplements or in nutraceuticals.

ABSTRACT:The study on the chemical constituents of an essential oil of Pogostemon cablin was carried out by hydrodistillation of leaf explants and the oil analysed by Gas Chromatography Mass Spectrometry (GC/MS). The oil yield was found to be 0.30 % (v/w) of fresh weight. Twenty two compounds were identified by GC/ MS as eighteen sesquiterpenes and three oxygenated sesquiterpenes. Among these, patchouli alcohol (60.30 %) was the major component, followed by germacrene A (11.73 %). In order to study the chemical constituents of the essential oil of plant cell cultures, leaves were surface sterilised and callus cultures initiated on MS media containing naphthaleneacetic acid (0.5 mg/l), and benzyladenine (1 mg/l), followed by incubation in suitable culture conditions. Cell suspension cultures were initiated by subculturing callus cultures into new liquid media and maintained in the same conditions. Chemical constituents of the essential oils produced by both callus and cell suspension cultures were extracted with dichloromethane and analysed by GC and GC/ MS. The results showed that essential oil obtained from these cultures contained the same major constituents, namely patchouli alcohol, as in the intact plant, but the level was low, and also contained a small amount of minor constituents. Feeding cis-farnesol, the precursor of patchouli alcohol, to cell suspension cultures resulted in the patchouli alcohol being increased from 19.5 mg/l to 25.5 mg/l.

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