Green extraction of polyphenols from citrus peel by-products and their antifungal activity against Aspergillus flavus

Food Chem X. 2021 Oct 25:12:100144. doi: 10.1016/j.fochx.2021.100144. eCollection 2021 Dec 30.

Abstract

Aspergillus flavus is a pathogenic fungus associated with food safety issues worldwide. This study investigated the antifungal activity of citrus peel extracts prepared using food-grade solvents (hot water or ethanol). Mandarin (Citrus reticulata) peel ethanol extracts inhibited the mycelial growth of A. flavus (39.60%) more effectively than those of orange (32.31%) and lemon (13.51%) after 7 days of incubation. The growth of A. flavus could be completely inhibited by mandarin extracts at 300-400 mg mL-1, depending on the extraction solvent. Solid-phase extraction (SPE) separated the polyphenol-rich fractions, which showed up to 40% higher antifungal activity than crude extracts. Twelve polyphenols (2 phenolic acids and 10 flavonoids) were identified by HPLC-DAD, narirutin and hesperidin were the most abundant. In conclusion, citrus peels are promising bioresources of antifungal agents with potential applications in food and other industries.

Keywords: Antifungal activity; Aspergillus flavus; CE, Crude extract; Citrus sp.; EF, Elution fraction; MIC, Minimum inhibitory concentration; PDA, Potato dextrose agar; PDB, Potato dextrose broth; PMF, Polymethoxylated flavones; Polyphenols; SPE, Solid phase extraction; Solid Phase Extraction; TFC, Total flavonoids content; TPC, Total phenolic content; WF, Washing fraction.