Proximate Compositions and Antibacterial Activity of Citrus sinensis (Sweet Orange) Peel and Seed Extracts

Abstract

Aim: This study evaluated the proximate composition and antibacterial activity of the Citrus sinensis (sweet orange) fruit waste (peels and seeds). Study Design: The peels and seeds from Linnaeus Osbeck variety of Citrus sinensis (sweet orange) fruits purchased from Eke-Okigwe market in Imo State, Nigeria were respectively investigated for proximate composition and antibacterial activity. Place and Duration of Study: The study was conducted at the department of Biochemistry, Michael Okpara University of Agriculture Umudike, Nigeria between May and August, 2015. Methodology: The proximate content in the respective sample flour and the antibacterial activity of the respective sample crude ethanol (95%) and water extracts were determined by standard methods. Each extract (100 mg/ml) was tested against two bacteria - Escherichia coli and Staphylococcus aureus. Results: The percentage yield for the seeds sample (54.49%) was lower (p<0.05) than that for the peels (90.21%). Proximate contents (%) in the dried flour seeds and peels samples respectively were as follow: fat/oil (11.08±0.47, 6.24±0.06), moisture (8.32±0.32, 9.68±0.07), carbohydrate (67.83±0.32, 54.17±1.09), ash (3.02±0.09, 4.89±0.06), fibre (2.98±0.14, 13.99±0.06) and protein (6.77±0.10, 11.00±0.10). The water extract of the orange peels and seeds, respectively showed activity (measured as inhibition zone diameter, IZD in mm) against Escherichia coli (11.33±1.52, 9.67±1.15) and Staphylococcus aureus (14.00±1.00, 8.67±1.15) with the activity elicited by the peels extract in either case significantly (P<0.05) higher. Similarly, the activity (mm) by the ethanol extract of the orange peels against Escherichia coli (20.00±1.73) and Staphylococcus aureus (19.00±1.73) was respectively higher (p<0.05) than that by the seeds (12.33±0.38, 13.33±1.16). Conclusion: The study demonstrated the preponderance of the proximate contents in the samples, and activity of the extracts against the tested bacteria. Further studies to harness these findings may improve possible nutraceutical applications of the sweet orange fruit wastes and minimize the attendant environmental waste burden, hence are warranted.