Quantitative phytochemical analysis and antimicrobial activities of fresh and dry ethanol extracts of Citrus sinensis (L.) Osbeck (sweet Orange) peels

Background Citrus sinensis is one of the most abundant citrus species consumed. Orange peels are a waste by-product of the fruit and may potentially contain useful phytonutrients with biological relevance. Methods Fresh and dry peels of sweet orange were subjected to Soxhlet extraction and then concentrated using a rotary evaporator. Total phenolic, flavonoid and tannin content were determined using standard methods. Antimicrobial activities against five (5) bacterial strains ( Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Escherichia coli and Salmonella typhimurium ) and three (3) fungal strains ( Candida albicans, Aspergillus niger and Penicillium notatum ) was carried out by observing the zone of inhibition using disc diffusion method. Results The total phenolic, flavonoid and tannin content was higher in the fresh peel extract compared to the dry peel extract. Antimicrobial activities revealed that the fresh peel extract had better antibacterial activities against all bacterial strains and one fungal strain studied compared to the dry peel extract. Growth of Aspergillus niger and Penicillium notatum were however better inhibited by the dry peel extract than the fresh peel extract. Conclusion This study investigated the phenolic content and antimicrobial activities of fresh and dry Citrus sinensis peel extracts. The results from the study conclude that the fresh Citrus sinensis peel extract contains more phenolics and possesses better antimicrobial activities against the studied microbial strains compared to the dry peel extract. The findings in this study suggest that drying plant parts before extraction for phytonutrients may lead to loss of active components.