Metabolomics, antioxidant, and enzyme inhibitory effects of Citrus aurantium fruits

GC-MS revealed nootkatone (15.29%), decyl anthranilate (11.58%), neryl acetate (7.83%), and linalool acetate (6.83%) as major components of fruit extract; while the leaves extract contained mainly lupeol (24.32%), linalool (16.47%), friedelan-3-one (16.40%) and linalool acetate (12.31%). The extracts showed potential inhibitory activities against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, amylase, and glucosidase enzymes. Results were confirmed by in silico molecular docking studies on the respective enzymes' active sites, viz NADPH oxidase, BChE, tyrosinase, α-amylase, and α-glucosidase. Amongst the docked compounds, lupeol showed the best binding affinities to NADPH oxidase, butyrylcholinesterase BChE, and α- glucosidase; while linalool acetate and neryl acetate showed the best activities against tyrosinase and α-amylase enzymes, respectively. In conclusion, bitter orange waste products can be a potentially important source of antioxidants and useful supplements.