This study investigated the antioxidant and anti-inflammatory activities of g-oryzanol rich extracts from Thai glutinous purple rice bran. Five purple rice bran samples, PAH E-KAW,GAM PEUAK, NIAW DAM, GAM THOR and GAM BOUNG were obtained from local glutinous cultivars in Northern Thailand. The g-oryzanol rich extracts were prepared by soxhlet extraction and semi-purified by column chromatography. The extracts contained g-oryzanol in the range of 1.23 to 9.14% w/w. The extracts containing more than 5% w/w of g-oryzanol (PAH E-KAW, GAM THOR and GAM BOUNG) were selected for investigation of antioxidant and anti-inflammatory activities; and first standardized by adding the equivalent amount of each extract to give 10% w/v g-oryzanol. All of extracts exerted moderate ABTS·+ and superoxide anion scavenging activity. GAM BOUNG exhibited the highest ABTS·+ scavenging activity with VCEAC value of 201.3 ± 1.84 mg L-ascorbic acid/ gram extract, TEAC value of 267.2 ±2.96 mg Trolox/ gram extract and QEAC value of 137.4 ± 3.41 mg Quercetin/ gram extract followed by PAH E-KAW and GAM THOR, respectively. GAM BOUNG also showed the highest activity on superoxide anion scavenging at IC50 = 12.56 ± 0.13 mg/ml followed by GAM THOR and PAH E-KAW. Furthermore, GAM BOUNG exhibited a strong inhibition effect on linoleic acid peroxidation (IC50 = 36.79 ± 2.97 mg/ml). Additionally, all of the extracts showed a strong anti-inflammatory activity through inhibitory effect on nitric oxide (NO) production in combined LPS-IFN-g-activated RAW 264.7 murine macrophage cells. GAM BOUNG exhibited the highest inhibitory effects on NO production (IC50 = 29.32 ± 2.21 mg/ml), without exerting cytotoxicity followed by GAM THOR and PAH E-KAW. These results indicate that g-oryzanol rich extracts from Thai glutinous purple rice bran are acting as a lipophilic radical scavenger better than a hydrophilic radical scavenger. Moreover, these extracts exert a potent anti-inflammatory activity.
Key words: Purple rice bran, g-oryzanol, antioxidation, anti-inflammatory.
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