Antimicrobial potential of exotic fruits residues

Abstract

The antibacterial potential of extracts from the residues of fruits dekopon, kiwifruit, blueberry, sapodilla, tamarillo (peel), and noni (peel, seed and mixture of peel and seed) was evaluated against Gram-positive bacteria viz. Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, and Staphylococcus aureus and the Gram-negative bacteria, Escherichia coli, Pseudomonas aeruginosa, Salmonella enteritidis, and Serratia marcescens. It was found that extracts of mixture of noni seed and peel residues in acetone 40–80%, ethanol 40–80% and methanol 50–80% were effective against 4, 3 and 2 bacteria, respectively, being B. cereus and S. marcescens not inhibited by any extract. Highlight to the extract of mix noni seed and peel in 80% ethanol which was most effective against E. coli and S. aureus, with diameters of the inhibition zone (DIZ) around 14.0 mm. The extracts of dekopon peel in methanol 50, 70 and 80% and extract of kiwifruit peel in ethanol 40% were the only ones that showed antimicrobial potential, inhibiting S. enteritidis and S. aureus, respectively (DIZ of 9.0 mm). The extracts of blueberry peel were most effective against the Gram-negative bacteria, being E. coli and S. marcescens more sensitive to extracts of this residue in 80% and 70% ethanol (DIZs of 12–13 mm), respectively. The extracts of sapodilla peel in 70% and 80% acetone were more effective against Gram-positive bacteria, with DIZs between 10.0 and 12.0 mm. Finally, the extracts of tamarillo peel only inhibited E. faecalis (extracts in 60 and 70% ethanol), E. coli (extracts in 50–80% ethanol) and S. enteritidis (extract in methanol 80%). The minimum inhibitory concentration (MIC) and minimum bactericide concentration (MBC) were determined for the bacteria more sensitive to extracts of fruits residues. The selected extracts inhibited the bacteria with the lowest MIC of 0.39 mg/mL and eliminate with MBC values > 200 mg/mL. However, the 70% ethanol blueberry peel extract was the highlight, since that inhibited and eliminated E. coli with the lowest concentration (0.39 mg/mL). In this study, the residues of these exotic fruits, which are commonly discarded, showed a great potential for use as natural antibacterial therapies.