Abstract

The treatment of diabetes mellitus is not yielding the desired positive effect in some individuals, coupled with the side effects of existing synthetic drugs. As a result, this study aimed to identify and quantify the phenolic compounds, evaluate the antioxidant capacity, and assess the in vitro anti-inflammatory and antidiabetic effects of the methanolic extract of L. leonurus (MELL) leaves. The bioactive phytoconstituents in MELL were analysed using UPLC-ESI-QTOF-MS. Then, in vitro investigations such as (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide assay, α-glucosidase inhibition, glucose uptake assay, pancreatic β-cell proliferation assay, macrophage activation in L6 myoblasts, and C3A hepatocytes were performed. The polyphenol content was estimated to be 43.03 ± 1.28 mg gallic acid equivalent per gram, and the flavonol content was 40.43 ± 1.75 mg quercetin equivalent per gram. For the antioxidant capacity, ferric reducing antioxidant property was estimated to be 197.42 ± 9.78 μmol AAE/g, 2,2-diphenyl-1-picrylhydrazyl was 115.45 ± 3.08 μmol trolox equivalent per gram (TE/g), and trolox equivalent capacity was 105.77 ± 2.30 μmol (TE/g). MELL exhibited α-glucosidase inhibition in a dose-dependent manner with the maximum activity recorded at 1,000 μg/ml and an IC50 of 500 μg/ml. It enhanced glucose utilization and uptake in L6 myoblasts and C3A hepatocytes. Interestingly, no significant cytotoxic effect was recorded for the extract in L6 or C3A cells. It also exhibited anti-inflammatory activity from a concentration of 10 μg/ml when screened against RAW 264.7 cells without a significant cytotoxic effect. The results of the study demonstrated the potential of L. leonurus in the management of diabetes, indicating a reservoir for isolating lead compounds with potential applications in the development of novel antidiabetic drugs.

Key words: Leonotis leonurus, antidiabetic activity, glucose uptake, L6 myoblasts, C3A hepatocytes cells