Rambutan (Nephelium lappaceum L.) Shell as a Source of Polyphenols: Chemical Characterization and Biological Activities

This study investigates the valorization of Nephelium lappaceum (rambutan) shell, an agro-industrial byproduct, as a sustainable source of bioactive compounds through comprehensive chemical and functional characterization. Phytochemical profiles were determined using spectrophotometrics and HPLC-DAD-MS/MS, revealing a composition dominated by ellagitannins (e.g., geraniin, corilagin, chebulagic acid) and ellagic acid derivatives, alongside significant levels of total phenolics (25,982.2 mg/100 g DW) and anthocyanins. The extract exhibited strong antioxidant activity (DPPH IC50 = 8.02 μg/mL; TEAC = 5703.92 μmol TE/g), consistent with its high phenolic content. Biological evaluation demonstrated antimicrobial activity against a broad panel of Gram-positive and Gram-negative bacteria, including multidrug-resistant strains, with greater efficacy against Gram-positive species (Staphylococcus aureus, MIC = 2.5 mg/mL). The extract also showed significant antibiofilm activity, achieving up to 93% inhibition. Antitumoral assays revealed selective cytotoxicity, particularly against HeLa cells (IC50 = 260 μg/mL; TI = 11.5), indicating preferential effects on tumor over non-tumor cells. Importantly, hemolytic assays confirmed low toxicity, with negligible erythrocyte membrane disruption across tested concentrations. Overall, these findings highlight rambutan shell as a rich source of phenolic bioactives with multifunctional biological properties and favorable safety profile, supporting its potential application in nutraceutical and pharmaceutical formulations within a circular economy framework. This study aligns with SDG 3 and SDG 9 by promoting the valorization of agro-industrial waste as a source of safe bioactive compounds for health-related applications.