Bioactive and Antimicrobial Properties of Eggplant (Solanum melongena L.) under Microwave Cooking

Fruits and vegetables constitute a considerable amount of antioxidants and among them eggplant is a rich source of polyphenol compounds. This study investigated the bioactive and antimicrobial properties of eggplant under different degree of microwave cooking. The eggplant was cooked for 7 min (light cooked), 10 min (medium cooked), and 15 min (high cooked). The highest total polyphenol content was observed in the light cooked eggplant sample (27.35 mg gallic acid equivalent (GAE)/g dry weight (DW)) followed by high cooked sample (26.10 mg GAE/g DW), while the lowest total polyphenol content (2.79 mg GAE/g DW) was obtained for the uncooked (control) sample. The total polyphenol content of the samples ranged in the following order; light cooked > high cooked > medium cooked > uncooked. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging of eggplant ranged between 16.16% (control) and 47.88% (high cooked). The highest reducing power was exhibited by the light cooked (absorbance 1.708) eggplant sample followed by the high cooked (absorbance 1.597), while the lowest reducing power was shown by uncooked sample (absorbance 0.389). Moreover, antimicrobial studies showed that light cooked eggplant sample demonstrated broad-spectrum inhibition of growth in Gram-positive as well as Gram-negative bacteria and Candida albicans. Slightly lower antimicrobial potential was exhibited by medium cooked eggplant sample while no antibacterial or antifungal activity was recorded for the extract of high cooked eggplant sample. Microwave cooking might be a method to enhance the antioxidant and antimicrobial potential of eggplant.