Exploring the bioactive potential of Citrus reticulata pomace: Extraction, characterization, and applications

Citrus pomace, a major by-product of the juice processing industry, presents significant potential for valorization due to its rich bioactive compounds and dietary fiber content. This study investigates the physicochemical properties of C. reticulata pomace and evaluates various solvents, their concentrations, and both conventional (Soxhlet, maceration) and novel (ultrasound-assisted and microwave-assisted) extraction techniques for recovering bioactive compounds. Among these, ultrasonication achieved the highest total phenolic content (3.64 mg GAE/g pomace) and antioxidant activity (65.75 % DPPH reduction) using 80 % ethanol. HPLC analysis identified major phenolic compounds, including gallic acid (307.13 ± 3.21 µg/g), p-coumaric acid (178.19 ± 2.63 µg/g), chlorogenic acid (319.26 ± 14.34 µg/g), ferulic acid (1409.35 ± 5.16 µg/g), hesperidin (1273.29 ± 6.59 µg/g), and quercetin (313.67 ± 9.61 µg/g). In-vitro bio-accessibility studies revealed that 42–45 % of phenolic compounds and 70 % of antioxidant activity remained bioavailable after digestion, indicating their potential health benefits. Additionally, the phenolic extract exhibited significant antimicrobial activity, with inhibition zones of 12.49 mm against Bacillus subtilis and 7.18 mm against Aspergillus niger, demonstrating its broad-spectrum antimicrobial potential. These findings highlight the value of C. reticulata pomace as a sustainable and cost-effective source of bioactive compounds for applications in functional foods, natural preservatives, and nutraceuticals.