Measurement of total phenolic content and antioxidant activity of aerial parts of medicinal plant Coronopus didymus

Objective: To evaluate the total phenolic content and compare the antioxidant activity of various solvent extracts and fractions from the aerial parts of Coronopus didymus through various assays. Methods: Total phenolic content was determined using the Folin-Ciocalteu assay and the in vitro antioxidant activity of a number of different extracts was investigated in a dose-dependent manner with three different methods: the 2,2-diphenyl-l-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and ferric reducing antioxidant power (FRAP) assays. A flavone was isolated from the most active ethanolic extract with high antioxidant activity using size exclusion chromatography. IC50 values were calculated for the DPPH and ARTS methods. The FRAP activity was assessed in terms of mu M Fe (II) equivalent. Results: The phenolic content was found to be highest in the ethanol extract (CDA Et; 47.8 mM GAE) and the lowest in the dichloromethane extract (CDA DCM; 3.13 mM GAE). The ethanol extract showed high radical scavenging activity towards DPPH and ABTS radicals with 105 values of (7.80 x 10(2)) and (4.32 x 10(2)) pg/mL, respectively. The most active ethanol extract had a FRAP value of 1 921.7 mu M Fe (II) equivalent. The isolated flavone FlOC (5,7,4'-trihydroxy-3'-methoxy flavone) was far more effective for scavenging free radicals in the DPPH and ABTS assays with 105 of 43.8 and 0.08 mu g/mL, than the standard trolox. with IC50 values of 97.5 and 21.1 mu g/mL, respectively. In addition, the flavone FIOC and the standard ascorbic acid had FRAP values of 1 621.7 and 16038.0 mu M Fe (II) equivalents, respectively. Conclusions: The total phenolic content of extracts in decreasing order is ethanol extract (CDA Et)> acetone extract (CDA ACE)> phenolic extract (CDA MW)> n -hexane extract (CDA nHX)> chloroform extract (CDA CHL)> dichloromethane extract (CDA DCM). The ordering of extracts in terms of antioxidant activity from highest to lowest is CDA Et> CDA MW> CDA DCM> CDA CHL> CDA ACE> CDA nHX in DPPH, ARTS and FRAP assays. A significant relationship is found between antioxidant potential and total phenolic content, suggesting that phenolic compounds are the major contributors to the antioxidant activity of Coronopus didymus.