Ultrasonic‐assisted extraction of bioactive compounds from eggplant ( Solanum melongena L. ) calyx and evaluation of extract properties

Abstract Background Eggplant ( Solanum melongena L.) is widely consumed worldwide and generates considerable waste, including peel and calyx, during processing and consumption. Although often considered as by‐products, these wastes are rich sources of bioactive compounds, which vary depending on the plant variety and cultivation location. Given that no studies have been reported on the bioactive compounds of the Iranian eggplant calyx, this study examines the extraction of bioactive compounds from the calyx of Iranian purple eggplant using a combined solvent and ultrasonic‐assisted extraction method, including the determination of total phenolic and flavonoid contents and antioxidant capacity. Results The total phenolic content of hydroalcoholic and aqueous extracts was 8.72 ± 0.12 and 7.44 ± 0.041 mg gallic acid equivalents/g dry extract, respectively. Total flavonoid contents were 52.60 ± 1.15 and 49.44 ± 1.90 mg rutin equivalents/g dry extract. Both extracts showed strong antioxidant activity with 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging percentages of 82.77% and 82.51%, and IC50 values of 1.47 and 4.16 mg/mL, respectively. Liquid chromatography–mass spectrometry profiling of the hydroalcoholic extract identified major bioactive compounds, including p ‐coumaric acid, caffeic acid, catechin, myricetin, rutin, luteolin, and kaempferol. Conclusion These results underscore the efficacy of ultrasonic‐assisted solvent extraction in isolating phenolic and flavonoid compounds from eggplant calyx. Considering the abundance and accessibility of this plant material, coupled with its significant bioactive compound content, the eggplant calyx emerges as a promising, cost‐effective source for the development of functional ingredients in the food, pharmaceutical, and cosmetic sectors, particularly in developing countries.