Effect of ethanol concentration, extraction time and extraction temperature on the recovery of phenolic compounds and antioxidant capacity of Centella asiatica extracts

The present study was to optimize the phenolic recovery from Centella asiatica by investigating the effects of ethanol concentration (0-100%, v/v), extraction time (60-300 min) and extraction temperature (25- 65°C) on phenolic extraction using single-factor experiments. Total phenolic content (TPC), total flavonoid content (TFC) and condensed tannin content (CTC) were used for determination of phenolic content while 2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical-scavenging capacity and 2,2’-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging capacity were used for measuring the antioxidant capacity of C. asiatica extract. All extraction conditions had significant effect (p 0.05) on the phenolic contents and antioxidant capacities of C. asiatica extract. The optimal conditions for phenolic recovery were 40% ethanol for 60 min at 65°C, with values of 1203.49 mg GAE/ 100 g DW for TPC, 561.92 mg CE/ 100 g DW for TFC, 181.25 mg CE/ 100 g DW for CTC, 730.37 μmol TEAC/ 100 g DW for ABTS and 1948.30 μmol TEAC/ 100 g DW for DPPH. TFC was found to be positive correlated significantly (0.902, p 0.05) with DPPH under influence of ethanol concentration. However, all antioxidant compound assays (TPC, TFC and CTC) were negatively correlated significantly with ABTS under the effect of extraction temperature.