Antioxidant Activities and Identification of an Active Compound from Rambutan (<i>Nephelium lappaceum</i> L.) Peel

The consumption of rambutan fruit resulted in a vast amount of peels and
seeds waste. Therefore, the exploration of active compounds having beneficial effects on
human health, such as antioxidants, is very lucrative. This research was aimed to isolate
and to identify the active compound as an antioxidant from rambutan peel. The
powdered rambutan peel was extracted with a maceration technique using methanol then
fractionated using petroleum ether, chloroform, and ethyl acetate to get the corresponding
fractions. The extract and fractions were determined for its antioxidant activities in vitro
using 2,2’-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and metal-chelating
assay. The ethyl acetate fraction exhibited the highest antiradical activity with an IC50
value of 26.22 μg/mL and metal-chelating activity, accounting for 12.32%. The
antioxidant activities of extract and fractions correlated with its phenolics and flavonoid
contents. Identification of active compounds using FTIR, GC-MS, and NMR resulted in
the chemical formula of C7H6O4, identified as 3,4-dihydroxybenzoic acid.