Comparison between MRQ74 and MRQ76 rice brans on antioxidant capacity

In Malaysia, rice bran is typically discarded or repurposed as animal feed, fertiliser, or fuel. However, a previous study had revealed that rice brans rich in bioactive compounds that could give health benefits similar to rice itself. Therefore, as a pioneer of local fragrant rice varieties in Malaysia, the study aimed to compare the antioxidant capacity of fragrant MRQ74 and MRQ76 rice brans. The two varieties from the Malaysian Agricultural Research and Development Institute (MARDI) were used to study their proximate analysis for moisture and ash contents (oven drying method), crude fat (Soxtherm method), crude protein (Kjeldahl method), crude fibre (Gravimetric method), carbohydrate and energy. Total phenolic and flavonoid contents were determined by Folin-Ciocalteu and Aluminium Chloride Colourimetric methods, while antioxidant capacity was assessed through 2,2-diphenylpicrylhydrazyl (DPPH) assay and Ferric Reducing Antioxidant Power (FRAP) assays of different solvent (methanol, ethanol, water) extracts. MRQ76 rice bran exhibited higher nutritional values (ash 2.08 g/100 g; crude fat 5.00 g/100 g; crude fibre 17.17 g/100 g; energy 379.12 kcal) compared to MRQ74 rice bran. The highest total phenolic content was observed in ethanol for MRQ74 rice bran (3568.54±0.03 mg GAE/100 g), while the water solvent exhibited the highest total flavonoid content in MRQ76 rice bran (1325.06±0.01 mg GAE/100 g). MRQ74 rice bran sample had a lower IC50 value and a higher TEAC value (0.70 mg/mL IC50; 22.86 TEAC) in methanol and the FRAP value (294.15±0.00 to 580.70±0.01 nM Ferrous Equivalent/100 g), signifying greater reduction capability of the sample's antioxidant activity extracted with methanol. Correlation results indicated that the higher phenolic content in MRQ74 rice bran had higher antioxidant capacity compared to MRQ76 rice bran. Methanol emerged as superior in assessing antioxidant capacity in both samples, extracting more antioxidant compounds and demonstrating high antioxidant capacity. Hence, the findings proved that MRQ74 and MRQ76 rice brans could provide valuable nutritional potential insights that are employed in the culinary and pharmaceutical sectors for future conversion of this agricultural waste into beneficial human products.