Enhancement of Antioxidant Activity and Inhibition of Polyphenol Oxidase from Green Oak Lettuce by Chitosan-Encapsulated Rambutan (Nephelium lappaceum L.) Peel Extract
Panita Kongsune, Kittisak Sangthongchin, Phasin Ampha, Manee Maneechote and Netnapa Chana* Author for corresponding; e-mail address: netnapa@tsu.ac.th
Volume: Vol.52 No.4 (July 2025)
Research Article
DOI: https://doi.org/10.12982/CMJS.2025.035
Received: 7 January 2025, Revised: 31 March 2025, Accepted: 14 April 2025, Published: 1 July 2025
Citation: Kongsune P., Sangthongchin K., Ampha P., Maneechote M. and Chana N., Enhancement of antioxidant activity and inhibition of polyphenol oxidase from green oak lettuce by chitosan-encapsulated rambutan (Nephelium lappaceum L.) peel extract. Chiang Mai Journal of Science, 2025; 52(4): e2025035. DOI 10.12982/CMJS.2025.0035.
Graphical Abstract
Abstract
Enzymatic browning in fresh-cut lettuce remains a critical challenge in the food industry, driving the search for effective natural preservatives. This study explores the innovative encapsulation of rambutan (Nephelium lappaceum L.) peel bioactive compounds with chitosan to enhance their stability and bioactivity. Among the various rambutan peel extracts (RPE) evaluated, the methanolic extract exhibited the highest DPPH scavenging activity (IC50: 2.28 ± 0.15 μg/mL), correlated with its total phenolic content. The ethanolic extract also demonstrated strong antioxidant activity (IC50: 3.26 ± 0.17 μg/mL) and was selected for further studies due to its balanced antioxidant performance and suitability as a food-grade solvent for potential commercial applications. Liquid chromatography-mass spectrometry (LC-MS) analysis identified Sanguiin H11 and ellagic acid as the key phenolic compounds. Notably, ellagic acid demonstrated strong molecular docking with polyphenol oxidase (PPO), showing a binding energy of -6.75 kcal/mol through specific hydrogen bonding through HIS296 interactions. The molecular docking results indicated that ellagic acid has a superior binding affinity compared to the reference inhibitor tropolone (-5.20 kcal/mol). The optimized chitosan encapsulation system (10:1 w/w RPE: chitosan ratio) produced uniform spherical microcapsules (3403 ± 8.79 nm) with excellent colloidal stability (zeta potential: 31.17 ± 0.83 mV) and high encapsulation efficiency (60.53 ± 0.48%). This formulation significantly enhanced both DPPH radical scavenging activity (6.99-fold increase) and green oak lettuce polyphenol oxidase (goPPO) inhibition (2.29-fold improvement) compared to the chitosan control group. This research demonstrated the successful conversion of agricultural waste into effective natural preservatives with PPO inhibitory and antioxidant activities, offering a promising solution for fresh-cut produce preservation.