Ultrasonic assisted aqueous extraction of catechin and gallic acid from Syzygium cumini seed kernel and evaluation of total phenolic, flavonoid contents and antioxidant activity

Abstract

Present work reported ultrasonic-assisted aqueous extraction (UAE) of bioactives from Syzygium cumini seed kernels powder (SCSKP) as an alternative to conventional, soxhlet and stirred batch techniques. The yield of catechin, gallic acid, TPC (Total phenolic contents), TFC (Total flavonoid contents) and IC50 value obtained was 2.2, 54.5 mg/g, 100.07 mg of gallic acid equivalent (GAE)/g of SCSKP, 10.11 mg of catechin equivalent (CE)/g of SCSKP and 10.59 μg/mL respectively in 12 min. extraction time when other optimum parameters were used asSCSKP to the water ratio 1:15, temperature 35°C, power 125 W, and duty cycle 60 % (1.2 min. ON and 0.8 min. OFF). TPC, TFC and antioxidant activity of the extract were determined by using Folin Ciocalteu (FC), AlCl3 and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays. The optimized stirred batch technique was used for sequential batch extraction till 5 stages giving catechin and gallic acid yield of 1.05 mg/g and 53.3 mg/g, respectively. UAE technique not only enhanced the yield of catechin, gallic acid, TPC, TFC by 3.6, 1.5, 1.3, 1.4 times respectively and antioxidant activity by 1.2 times but also reduced the extraction time, amount of solvent and temperature by 8.8, 1.3 and1.4 times respectively as compared to conventional stirred batch technique.