Bioactive Compounds and Biological Activity of Pontianak Orange Peel (Citrus reticulata) Extract Obtained by Supercritical Fluid Extraction: A Green Chemistry Approach for Sustainable Utilization of Agricultural Waste Shofi Indriyani1, Yulia Anita2*, Antonius Herry Cahyana1, Egi Agustian2, Megawati Megawati3, Tuti Wukirsari1*
1 Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, 16424, Indonesia
2 Research Center for Molecular Chemistry, National Research and Innovation Agency (BRIN), Serpong, 15314, Indonesia
3 Research Center for Pharmaceutical Ingredients and Traditional Medicines, National Research and Innovation Agency (BRIN), Serpong, 15314, Indonesia
Abstract
Pontianak orange (Citrus reticulata) peel is an agricultural by-product rich in bioactive compounds with potential pharmaceutical applications. This study aimed to characterize the bioactive compounds and evaluate the biological activity of Pontianak orange peel extract obtained through Supercritical Fluid Extraction (SFE) as a green and sustainable extraction approach. Orange peels were dried, ground, and extracted using SFE. Chemical profiling was performed using GC-MS, while Total Phenolic Content (TPC) and Total Flavonoid Content (TFC) were determined using Folin-Ciocalteu and aluminum chloride colorimetric methods, respectively. Antioxidant activity was assessed via ABTS radical scavenging assay, and antibacterial activity was evaluated against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, and Pseudomonas aeruginosa using the disc diffusion method. The SFE process yielded 0.8% of extract. GC-MS analysis identified pentamethylflavone as the dominant compound with a peak area of 98.63%, while TFC values were 18.42 mg QE/g. Antioxidant activity showed an IC₅-₀- value of 0.17 mg/mL (ABTS). The extract exhibited stronger antibacterial activity against Gram-positive than Gram-negative bacteria, with the highest inhibition zone recorded against Bacillus subtilis at 14 mm. Pontianak orange peel extract obtained via SFE exhibited significant flavonoid content alongside promising antioxidant and antibacterial activities, supporting its potential as a natural bioactive source. The application of SFE as a solvent-minimizing green technology demonstrates a sustainable approach to agricultural waste valorization, contributing to eco-friendly development in the natural product industry.
