Antibacterial And Antioxidant Activity Elucidation Of Bioactive Compounds From Citrus Sinensis Peel Extract

Abstract

Increasing cases of drug resistance, unwanted side effects of existing antibiotics, and the reappearance of earlier known infections have demanded the need for new, safe and effective antimicrobial agents. The objective of this study was to determine the antibacterial and antioxidant activity of Citrus sinensis peel extracts against selected human pathogenic bacterial strains and examine the molecular interaction of isolated compounds with selected protein targets. Using maceration and ultrasonic assisted extraction methods, the peel of Citrus sinensis (300g, 150g) was extracted with ethanol to yield 20.99 g and 11.5 g with (7%, 7.5%) yields, respectively. Phytochemical analysis conducted on Citrus sinensis peel ethanol extract revealed the presence of alkaloid, flavonoid, tannins, steroids, phenol and terpenoid. Silica gel column chromatographic separation of the ethanol extract obtained from maceration afforded four compound 46, compound 47, compound 48 and compound 49. The structures of the isolated compounds were characterized using NMR spectroscopic techniques (1H NMR, 13C NMR, DEPT-135).GC-MS analysis of essential oil revealed the presence of 7 chemical components accounted for 99.84 % of the total compositions. The crude extract and isolated compounds were evaluated in vitro for their antibacterial activities using disc diffusion method against six bacterial strains. A promising zone of inhibition values were observed by crude (12.67±0.58mm), compound 49 (15.67±2.88mm) and compound 46 (12.00±0.00mm) against E. faecalis , S. typhimurium and P. aeruginosa respectively compared to gentamicin (13.00±1.73, 18.00±1.00 and 16.67±1.15 respectively).Also the essential oil showed a good zone of inhibition against S. aureus (14.33±1.52 mm) compared to gentamicin (18.67±0.58 mm). DPPH radical scavenging activity revealed that compound 46 showed IC50 value of 0.05 mg/mL compared to ascorbic acid 0.016 mg/mL. Using autodock, a molecular docking study was conducted. It was discovered that, among isolated compounds, compounds 48 had the highest and best scoring poses (lowest energy) against the E. coli gyrase B enzyme (-6.9 Kcal.mol), Human Peroxiredoxin 5 (-7.1 Kcal.mol), and S. aureus Pyruvate Kinase (-8.2 Kcal.mol).The findings of this study support the traditional uses of the Citrus peels for the treatment of infectious diseases especially Gram-positive strains.