Assessment of the antioxidant potential of anthocyanin-rich Extract of eggplant (Solanum melongena L.) and evaluation of its antimicrobial activity

Abstract

Eggplant peels (Solanum melongena L.), particularly the purple variety, contain high levels of anthocyanins, a type of flavonoid with promising medicinal properties. This study aims to investigate the antioxidant and antimicrobial potentials of anthocyanin-rich extract of eggplant peels. The anthocyanin-rich extract was obtained by maceration under acidic conditions. Preliminary qualitative phytochemical screening of the extract was done following standard procedures. The antimicrobial activity of the extract was evaluated against two bacterial (Escherichia coli and Staphylococcus aureus) and two fungal (Aspergillus niger and Candida albicans) strains using the agar well diffusion method. The antioxidant activity of the extract was assessed by the β-carotene bleaching assay. Preliminary phytochemical analysis confirmed the presence of anthocyanin, a type of flavonoid, in the purple-coloured peel extract. The extract demonstrated antibacterial activity against gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacterial strains. The inhibition zone diameters were 22 mm and 18 mm at 100 mg/mL and 10 mg/mL, respectively against both bacterial strains. The minimum inhibitory concentration (MIC) was 0.1 mg/mL for Staphylococcus aureus and 0.01 mg/mL for Escherichia coli. The extract demonstrated a concentration-dependent antifungal activity against Aspergillus niger and Candida albicans with MIC of 0.1 mg/mL for both fungal strains. The extract showed potent antioxidant activity with percentage activity as high as 74.26%. The anthocyanin content in the extract contributes significantly to its antioxidant activity. These observations therefore suggest the potential for use of eggplant extract as natural antimicrobial and antioxidant agents.