Antioxidant Activity of Different Parts of Nauclea subdita

Nauclea subdita (Taya) has been used empirically to treat hypertension patients in Kalimantan Island. Recent studies reported that hypertension is very closely related to oxidative stress. Natural antioxidants from plants act as radical scavengers by converting free radicals into less reactive substances. Therefore, a plant possessing antioxidant activity could be a promising agent as an alternative treatment for hypertension. This study aimed to determine the in vitro antioxidant activity of aqueous extract of the stem bark and leaves of Nauclea subdita. Assay methods used in this study were Ferric Reducing Antioxidant Power (FRAP), 2.2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS). Furthermore, a molecular docking study was performed to predict the potential antioxidant activity of several chemical constituents of the plant against protein kinase C. The results indicated that the antioxidant activity of Taya extracts increases linearly with its concentration, as also indicated by DPPH and ABTS assay. According to the ABTS assay, the stem bark and leaves extract possessed antioxidant activity with IC50 values of 1183.13 ppm and 116.42 ppm, respectively and 128.63 ppm and 26.95 ppm for DPPH assay. At the same time, the FRAP assay showed ferric reducing power, which correlates to its antioxidant activity. The Molecular docking study showed that two metabolites from the phytosteroid class (β-sitosterol and stigmast-4-en-3-one) yielded comparable activity with native ligands. Aqueous extract of Taya stem bark and leaves possess antioxidant capacity, which could be further studied as a potential agent to reduce oxidative stress in hypertension