Antioxidative activities and phytochemical content of different organs of longjack (Eurycoma longifolia Jack)

Free radicals are reactive chemical species produced inside the body or obtained from the environment, which can cause diseases such as cancer. Antioxidants are compounds that can scavenge free radicals. One of the potential plants as a natural antioxidant is longjack. This research aimed to assess the antioxidant activity of longjack's leaves, stems, and roots utilising 2,2-diphenyl-1-picrylhydrazyl (DPPH) and cupric ion reducing capacity (CUPRAC), as well as to evaluate total phenolic content (TPC), total flavonoid content (TFC), and the correlations between TPC and TFC with DPPH and CUPRAC antioxidant activity, along with the relationship between the two methodologies. Extraction was conducted via reflux employing n-hexane, ethyl acetate, and ethanol. The antioxidant activity was assessed using DPPH and CUPRAC methods, together with total phenolic content (TPC) and total flavonoid content (TFC), using UV-visible spectrophotometry. High-performance liquid chromatography identified the marker chemical in the ethanol extract of longjack leaves. The DPPH antioxidant activity of extracts from the leaves, stems, and roots of longjack ranges from 2.03 to 39.08mg AAE/g, whereas the CUPRAC activity ranges from 10.45 to 60.12mg AAE/g. The highest TPC was given by ethyl acetate stem extract (6.81±0.21 g GAE/100 g), while the highest TFC was given by ethyl acetate root extract (4.70±0.28g QE/100 g). Phenolic compounds showed great contribution in their DPPH and CUPRAC antioxidant activities. The two methods showed linear results in determining the antioxidant activities of the extracts. The marker compound was identified in the ethanol extract.