Phytochemical Screening and in vitro Antimicrobial Effect of Orange (Citrus sinensis) Ethyl Acetate Extract Silage

Abstract

Background and Objective: Secondary metabolites are complex compounds. Many citrus fruits contain such compounds in the skin, seeds and pulp that act as phytochemicals with bacterial growth-inhibiting, anti-fungal and anti-cancer activities. This study was designed to identify phytochemical compounds in ethyl acetate extracts of orange and assess their antibacterial activities. Methodology: An ethyl acetate extract of orange silage (EAEOS) at 250, 500, 750 and 1000 ppm was fermented for 28 days. Treatments were replicated four times. The samples were placed in a jar serving as a silo under anaerobic conditions. At the end of fermentation, phytochemical screening was performed. Data were analysed using analysis of variance under a completely randomized design. Results: The EAEOS contains alkaloid, flavonoid, steroid, triterpenoid, phenolic, saponin and coumarin compounds. The antibacterial activity of EAEOS was assessed using disc and MIC (minimum inhibition concentration) methods with Escherichia coli (E. coli ), Staphylococcus aureus (S. aureus), Salmonella typhi (S. typhi ) and Bacillus subtilis (B. subtilis). The extract inhibited the growth of all test organisms, with zones of inhibition ranging from 9.75±0.00 to 16.75±0.14 mm (E. coli ), 8.00±0.23 to 12.50±0.24 mm (S. aureus), 8.50±0.24 to 11.75±0.00 mm (S. typhi ) and 7.75±0.11 to 11.75±0.12 mm (B. subtilis). The MICs were 38.72±0.23 to 59.54±0.23% (E. coli ), 15.08±0.54 to 23.25±0.59% (S. aureus), 10.46±0.12 to 19.65±0.02% (S. typhi ) and 9.64±0.45 to 11.28±0.44% (B. subtilis). Conclusion: The tested EAEOS compounds exhibited inhibitory activities against both gram-positive (S. aureus, B. subtilis) and gram-negative (E. coli and S. typhi ) bacteria.