Itharat A, Uttama S and Makchuchit S
Background: Sang Yod rice is red-violet pigmented rice grown in the south of Thailand (Phattalung province) for over a century. It has been highly valued in the province over decades for its unique taste, nutritious value, and heath improving properties. In very recent years, particularly with Royal approval, it has attracted the attention of scientists who have described anti-oxidant properties of some of the constituents in the bran and in bran oil of Sang Yod rice. The objectives of our study were to develop optimum extraction and quantitative procedures for some of the main bioactive compounds in Sang Yod rice (γ-oryzanol, vitamin E, vitamins B1, B2 and B3), and to study the anti-inflammatory activity of extracts using inhibition of nitric oxide (NO) production in lipopolysaccharide (LPS) - induced murine macrophage RAW 264.7 cell line. Results: Sang Yod rice bran crude extracted by maceration in 95% ethanol exhibited the highest inhibitory effects on NO production with IC50 values of 15.59 ± 1.23 μg/ml; this extract also had high content of γ-oryzanol (317 mg %w/w) and vitamin E (211 mg %w/w). Rice bran extracted using soxhlet extraction using chloroform showed the highest contents of γ-oryzanol (344 mg %w/w). Rice bran extracts exhibited higher γ-oryzanol content than whole grain rice. The highest content of vitamin B1 and vitamin B2 were in Sang Yod rice bran extracted by boiling in water (91 and 88 mg %w/w of extract, respectively). Pure γ-oryzanol and vitamin B2 showed the highest NO inhibitory effects (IC50=1.27 and 7.78 μg/ml respectively). Conclusions: The anti-inflammatory of Sang Yod rice properties, appear to correlate to content of essential compounds, especially content of γ-oryzanol and vitamin E in Sang Yod rice bran extracts. The simple procedure of maceration with 95% ethanol of rice bran provides an extracts with high anti-inflammatory activity, with high content of anti-inflammatory and antioxidant compounds. This extract, easily produced from Sang Yod rice bran, is suggested as suitable for commercial preparation and marketing of formulation, containing high levels of essential compounds as functional health improving food products of this pigmented rice.