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.
The objective of this study was to develop an in-vitro acclimatization technique through relative humidity reduction for direct transplanting of woody species to ex-vitro. The survival percentage, growth efficiency and physiological characteristics of in-vitro acclimatized plantlets and ex-vitro adaptation were then evaluated. Thai neem (Azadirachta siamensis Val.) was selected for this research as it is a species with high potential for regenerating soils with high salt content. Twenty-eight day-old plantlets were transferred to environmental control chambers under controlled relative humidity (RH), which are 65±5% and 95±5% for low and high RH respectively, in order to acclimatize plantlets for 42 days. It was found that leaf water content, chlorophyll content and net photosynthetic rate (NPR) of plantlets acclimatized under low RH conditions were significantly higher than those acclimatized under high RH conditions (control). The relationship of leaf water content and chlorophyll content with NPR directly affects growth efficiency, leaf area and dry weight, of plantlets. After transplanting, the water relation system [water use efficiency (WUE), stomatal conductance (G) and transpiration rate (E)] and photosynthetic system [NPR, maximum quantum yield (F v /F m) and quantum efficiency of photosystem II (Φ PSII)] were measured at days 0, 1, 3 and 5. The plantlets acclimatized under low RH conditions showed higher physiological adaptation in G, NPR, F v /F m and Φ PSII , except E, than those acclimatized under high RH conditions. The plantlets acclimatized under low RH conditions protected water loss through the leaf tissues by the function of stomata closure as indicated by low E values. Consequently, the survival percentage of plantlets acclimatized under low RH conditions was higher by a factor of 2.3 than those acclimatized under high RH conditions. In-vitro plantlets acclimatized by reducing RH produced vigorous plantlets and directly transplanted to ex-vitro with a high survival rate of 87.5%.
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