Valorization of hydro-distillate of fruit peels of Citrus paradisi macfad. Cultivar. Foster: Chemical profiling, antioxidant evaluation and in vitro and in silico enzyme inhibition studies

The major commercial crops in Pakistan are citrus fruit trees, which are farmed extensively and serve as the country's principal source of foreign exchange. A local citrus plant, <i>Citrus paradisi</i>, variety Foster is famous for its valuable fruit and fruit juice, however, tons of peels of this fruit are thrown as waste, which otherwise can be utilized in formulating nutraceutical and cosmetics. In the present study, essential oil of fruit peels was obtained through hydro-distillation, which was then analyzed through GC-MS analysis and studied for its antioxidant and enzyme inhibition potential. GCMS analysis revealed the presence of several components; major were found to be limonene, α-terpineol, caryophyllene, <i>δ</i>-amorphene, elemol, γ-eudesoml, nootkatone and di-isooctyl phthalate. Although, the oil showed weak free radical inhibition, it was potentially active in CUPRAC, FRAP, phosphomolybdenum and metal chelating antioxidant assays. The oil also exhibited anti-glucosidase, anti-amylase activities and also exhibited potent inhibition of the enzyme tyrosinase, which makes it strong candidate for nutraceuticals and skin care products. The docking studies also substantiate our results and caryophyllene, γ-eudesoml and nootkatone showed good binding affinity α-glucosidase and α-amylase and all tested compounds showed the higher binding affinity towards the enzyme tyrosinase.