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 (IC50 = 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 (IC50 = 0.25 mg/mL). Among fractions, highest inhibition was noticed for the methanolic part of crude extract (IC50 = 0.10 mg/mL). Both the total crude extract (IC50 = 0.23 mg/ml) and methanolic part of plant extract (IC50 =0.36 mg/ml) showed α-glucosidase inhibition, whereas only moderate 15-lox inhibition was observed.