Antioxidant activity of yellow candle bush (Cassia alata) leaves extract and Bioactive fractions through LC-QTOF-MS/MS and molecular docking approach

Free radicals play a significant role in numerous cellular functions, such as cell signaling, metabolism, and defense mechanism. Cassia alata, well known as Yellow Candle bush or locally known as Ketepeng Badak, has been known to possess biological activities including antiinflamation and antidiabetic. This current study investigates the antioxidant potential of C. alata leaves crude extract and resultant fractions. DPPH, ABTS radical scavenging activity, and FRAP assay were evaluated for the determination of the antioxidant activity, while the active constituents in C. alata leaf extract and fractions were identified with LC-QTOF-MS/MS. Total phenolic, flavonoid, and DPPH radical scavenging activities were highest in the ethyl acetate fraction with IC50: 18.54±0.01μg/mL on DPPH assay. Meanwhile, butanol fraction exhibited the strongest activity in ABTS and FRAP tests with IC50 of 4.29±0.26μg/mL and 4.39±0.11μg/mL, respectively. An in silico study using a molecular docking technique was conducted to determine the free energy of binding between human heme oxygenase-1 (HO-1) with bioactive compounds contained in C. alataethanolic leaves extract. Molecular docking of the main constituents in C. alata ethyl acetate fraction showed a greater binding affinity for kaempferol-3-O-β-D-glucopyranoside (-8.95kcal/mol), followed by coclaurine (-7.94kcal/mol), quercetin (-7.66kcal/mol) and 3-Hydroxy-7-methoxy baicalein (-7.32kcal/mol). These results corroborate the potent antioxidant activity of C. alata extract and fractions and its use as possible antioxidant agents in the pharmaceutical industry.