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Enhancing Antioxidant Properties of Germinated Thai rice (Oryza sativa L.) cv. Kum Doi Saket with Salinity

Kamolchanok Umnajkitikorn, Bualuang Faiyue and Kobkiat Saengnil

The objective of this study was to investigate the possibility of enhancing the antioxidant properties of germinated rice seeds cv. Kum Doi Saket, a pigmented rice variety cultivated in northern Thailand, using salinity. Rice seeds were soaked in 0, 25, 75, 150, and 300 mM NaCl for 12 hours, sown on 0.7% agar supplemented with the same NaCl concentrations for soaking at 28 ± 2°C in the dark for 5 days. Germination percentage, growth of seedlings, antioxidant capacities, total phenolic content, and activities of Ascorbate Peroxidase (APX) and Catalase (CAT) were examined. The results showed that germination was not affected by 25 and 75 mM NaCl, but was significantly reduced by 17% and 100% under 150 and 300 mM NaCl, respectively. Fresh weight was not affected by 25 mm NaCl, whereas all NaCl concentrations significantly reduced the shoot length of germinated seeds. Root length was significantly reduced by 150 and 300 mM NaCl. Antioxidant capacities, quantified by DPPH and ABTS radical scavenging assays, and total phenolic content significantly increased in germinated seeds treated with 150 mM NaCl. A high positive correlation between antioxidant capacities and total phenolic content was found. APX activities increased with germination time, reached the highest peak on day 2 for the control, and on day 4 for salt treatments with 150 mM NaCl showing the highest activity. CAT activities of the control reached the maximum on day 2, whereas it showed different highest peaks for salt treatments; salinity reduced the activity of CAT during germination. These results suggest that antioxidant properties of Kum Doi Saket germinated rice seeds are enhanced by salinity stress of 150 mM NaCl. This is an alternative way to elevate antioxidant properties for consumption and for further pharmaceutical application of germinated Thai rice.