In this research, hydrodistillation ultrasonic-assisted green technique was applied to extract the essential oils from bitter orange peel. The effects of independent factors (volume/mass ratio (X 1 ), ultrasonic time (X 2 ) and hydrodistillation extraction time (X 3 )) on the quantitative, phenolic and antioxidant properties of essential oils were investigated. Linear and quadratic polynomial models with suitable ANOVA results (model p-values <0.0003, R 2 values of 0.84-0.95, adjusted R 2 values of 0.82-0.90, predicted R 2 values of 0.71-0.75, and lack of fit p-values >0.5) were used for fitting the responses. Two optimal extraction conditions for bitter orange peel essential oils were determined as follows: optimum responses (OR) with maximum essential oil volume (0.99 ml), maximum TPC (108.33 mg GAE/100 ml) and minimum IC 50 (251.56 µl) could be achieved at X 1 : 6.00 ml/g, X 2: 39.10 min and X 3 : 4.72 hr, and optimum phenolic compounds (OP) with maximum TPC of 190.75 mg GAE/100 ml could be obtained at X 1: 13.89 ml/gr, X 2: 3.75 min and X 3 : 4.92 hr. The most predicted values for optimum conditions were in good agreement with experimental data. The disk diffusion experiments showed high antimicrobial activities of the optimum essential oils against E. coli. The GC-MS results proved limonene was the main compound in both optimum essential oils. These bitter orange peel essential oils with suitable antioxidant and antimicrobial activities, and healthy compositions, could be considered as dietary and pharmaceutical supplements. Practical applicationsPeel wastes of bitter orange were used for green hydrodistillation ultrasonic-assisted extraction of essential oil. The optimum treatments indicated a good phenolic content with suitable antioxidant and antimicrobial activity. Limonene, a pharmaceutical monoterpene hydrocarbon, was the main component of the optimum essential oils.Therefore, these environmentally friendly extracted essential oils could potentially be applied in the food and pharmaceutical industries.

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