Phenolic profile and antioxidante activity of Nephelium lappaceum L. epicarp hydroethanolic extracts
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Nephelium lappaceum L., popularly known as rambutan, is a tropical fruit belonging to the Sapidaceae family. It is native to Asia, but widely distributed in other tropical regions, such as Latin America, Australia, and some African countries [1,2]. This fruit is very appreciated for its exotic appearance and pleasant taste, and its commercialization and processing has been growing all over the world [1-3]. However, only a small portion of this fruit is edible/processed, with up to 67% corresponding to its inedible epicarp, which can generate a high volume of bioresidues and economic losses [2,3]. In order to propose a valorisation of rambutan epicarp as a source of bioactive molecules, the present study aimed to identify its anthocyanin and non-anthocyanin phenolic compounds by High-Performance Liquid Chromatography coupled to a diode-array detector and a mass spectrometer functioning by electrospray ionization (HPLC-DAD/ESI-MS), and determine the antioxidant activity of its hydroethanolic extract by two in vitro assays: thiobarbituric acid reactive substances assay (TBARS) and oxidative haemolysis inhibition assay (OxHLIA). The rambutan epicarp extract presented seven phenolic compounds, among which two anthocyanin compounds (O-glycosylated delphinidin derivatives) and five non-anthocyanin compounds (ellagitannin derivatives), in a total concentration of 11.57±0.08 and 31.6±0.5 mg/g of extract, respectively. Delphinidin isomers, geraniin isomers, and ellagic acid were the compounds detected in higher concentrations. In terms of antioxidant activity, rambutan extract was able to inhibit the lipid peroxidation in a low concentration (EC50 value of 2.79 ± 0.03 μg/mL), and a moderate amount of extract was required to exert oxidative haemolysis inhibition (EC50 value of 72 ± 2 μg/mL).
The results obtained allow to conclude that rambutan epicarp could be an interesting matrix to be used as source of bioactive compounds for further application in food/pharmaceutical fields.
