Antibacterial and antioxidant activities of phenolic compounds extracted from autumn fruits by-products

In the last few decades there has been a dramatic increase in antibiotic resistant bacteria, particularly methicillin-resistant Staphylococcus aureus (MRSA), that not respond to conventional treatments. In this study, the antioxidant and antibacterial activities of phenolic compounds extracted from by-products resulting from the autumn fruit industry were evaluated.

Extraction of phenolic compounds from pomegranate, quince, loquat and persimmon industry by-products was performed using a mixture of ethanol/water (80:20). Antimicrobial susceptibility was tested against 10 MRSA strains: 5 MRSA isolated from human diabetic foot ulcers, 3 from healthy wild hares and 2 from consumption rabbits. Minimum inhibitory concentrations were determined by disc diffusion method using different concentrations of extracts (100, 75, 50, 25 and 10 mg/mL). Antioxidant activity was performed using the DPPH, CUPRAC and FRAP methods. Each determination was performed in triplicate.

The majority of the extracts had an inhibitory effect on the growth of MRSA strains from all origins with the exception of quince seed and peel extracts and pomegranate seed extracts. Pomegranate peel extracts had the highest inhibitory effect on all MRSA strains presenting halos with diameter around 18mm followed by persimmon calyx extracts. Regarding the antioxidant activity, the extracts with the highest antioxidant power were pomegranate leaf extract, followed by persimmon calyx extracts, quince leaf and loquat flower.

Extracts from by-products of several autumn fruits revealed a high antibacterial and antioxidant activities. These compounds may be used as antibiotic substitutes or adjuvants to combat antibiotic resistant bacteria or in food industry as food preservers.