Effect of Ultrasonic Extraction Regimes on Phenolics and Antioxidant Attributes of Rice (oryza sativa L.) Cultivars

The ultrasound-assisted magnetic stirrer was used as an effective extraction technique for the evaluation of total phenolic contents (TPC) and antioxidant potential of ten Pakistani brown rice cultivars. For this purpose, ultrasonic (240W frequency 50/60 Hertz) assisted magnetic stirrer coupled with three solvents methanol, ethanol, and isopropanol in pure and aqueous fractions (80:20) were used for the extraction of brown rice material. The extract yields of brown rice were obtained from 1.62 g/100g to 3.67 g/100g for all the varieties. Aqueous isopropanol preferably and methanol (80:20) showed best extraction yields on the dry mass basis of brown rice. The contents of total phenolics were determined as highest (496.9 mg GAE/kg) in Basmati Pak while lowest (137.7 mg GAE /kg) in non-basmati Irri-6 variety. For antioxidant activity, brown rice extracts of Basmati Pak showed the best potential at IC50 2.19 mg/mL against DPPH radical scavenging. Reducing the power of Basmati Pak was found highest at 0.85. Brown rice extract of Basmati 515 showed best ferrous ion metal chelation at 5.78 Eq. EDTA mg/100g.