Antioxidant activity and identification of bioactive compounds from leaves of Anthocephalus cadamba by ultra-performance liquid chromatography/electrospray ionization quadrupole time of flight mass spectrometry.

To evaluate the antioxidant potential of different extract/fractions of Anthocephalus cadamba (A. cadamba) (Roxb.) Miq. (Rubiaceae) and study the tentative identification of their active constituents. The extract/fractions were screened for antioxidant activity using various in vitro assays viz. DPPH assay, ABTS assay, superoxide anion radical scavenging assay, reducing power assay and plasmid DNA nicking assay. Total phenolic content of extract/fractions was determined by colorimetric method. An ultra-performance LC-electrospray-quadrupole-time of flight mass spectrometry method was used to analyse the active constituents of extract/fractions of A. cadamba. The ethyl acetate fraction was found to be most active fraction in all the assays as compared to other extract/fractions. The IC(50) value of ethyl acetate fraction (ETAC fraction) was 21.24 μg/mL, 1.12 μg/mL, 9.68 μg/mL and 57.81 μg/mL in DPPH assay, ABTS assay, reducing power assay and superoxide scavenging assay respectively. All the extract/fractions also showed the potential to protect the plasmid DNA (pBR322) against the attack of hydroxyl radicals generated by Fentońs reagent. The bioactive compounds were identified by UPLC-ESI-QTOF-MS, by comparing the mass and λ(max) with literature values. The potential of the extract/fractions to scavenge different free radicals in different systems indicated that they may be useful therapeutic agents for treating radical-related pathologic damage.