Investigation of extraction yield, chemical composition, bioactive compounds, antioxidant and antimicrobial characteristics of citron (Citrus medica L.) peel essential oils produced by hydrodistillation and supercritical carbon dioxide

Citron peel is a valuable by-product gained from the fruit processing industry, which can be utilized as a potential feedstock to extract important commercial compounds such as essential oils. This conversion process can play a main role in reducing pollution and saving the environment by reusing waste, in addition to producing added-value products. In the present study, to extract the essential oil from citron peel were applied various methods of hydrodistillation and supercritical CO 2 , and the different essential oils produced were evaluated and compared in terms of extraction yield, physical attributes, bioactive compounds, chemical compositions, antioxidant and antimicrobial activity. The results showed that higher amount of extraction yield (7.6%), total phenol (112.84 mg GAE/g), flavonoid compounds (33.38 mg QE/g) and limonene (the major volatile component of citron peel essential oil) (60.69%) belonged to the supercritical CO 2 sample. The DPPH scavenging activity and reducing power of all the essential oils increased in a concentration-dependent manner (50–2000 µg/mL). The treatments of hydrodistillation and supercritical CO 2 in the order recorded less and more IC 50 values in both DPPH and FRAP tests. The obtained data from assay of MIC, MBC and inhibition zone diameter represented that citron peel essential oils possessed the best antimicrobial activity against Staphylococcus aureus compared to Escherichia coli and Pseudomonas aeruginosa , respectively. Therefore, citron peel essential oil considering the high levels of volatile and bioactive compounds viz limonene, phenol and flavonoid and desirable characteristics of antioxidant and antimicrobial can be used as a natural functional additive in the food industry.