UHPLC, ATR-FTIR Profiling and Determination of 15 LOX, α-Glucosidase, Ages Inhibition and Antibacterial Properties of Citrus Peel Extracts

Diabetes mellitus (DM) has a worldwide prevalence with very alarming situation in low-income and developing countries including Pakistan. During this project, we investigated peels of two commonly used Citrus species, i.e., C. sinensis and hybrid Citrus ( C. nobilis and C. delicense ) for their antioxidant, antidiabetic, antiglycation, antimicrobial and anti-inflammatory activities. Initially the peels were dried and extracted with various solvents. Then, HPLC and ATR-FTIR analysis was performed and finally the extracts and fractions were analyzed for their biological properties. The HPLC and ATR-FTIR data showed the presence of phenolics and flavonoids. In C. sinensis peels, high concentration of phenolics (87.3 ± 0.11 mg/g GAE) were observed in ethyl acetate part followed by methanolic fraction (72.5 ± 0.12 mg/gGAE). Both extracts exhibited strong antioxidant activity, antimicrobial and anti-biofilm properties. In Advanced Glycation End Products (AGEs) assay, total extract of C. sinensis showed moderate (IC 50 = 1.23 mg/mL) activity. All tested fractions were active in respect of α-glucosidase inhibition, whereas in 15-lox assay, only n -hexane fraction presented excellent activity (90%). On the other hand, in case of hybrid Citrus , a moderate inhibition was found in the case of total extract (IC 50 = 0.25 mg/mL). Among fractions, highest inhibition was noticed for the methanolic part of crude extract (IC 50 = 0.10 mg/mL). Both the total crude extract (IC 50 = 0.23 mg/ml) and methanolic part of plant extract (IC 50 =0.36 mg/ml) showed α-glucosidase inhibition, whereas only moderate 15-lox inhibition was observed.