Therapeutic Potential of Silybum marianum and Pergularia tomentosa Extracts from Jordanian Origin in Diabetes Mellitus

Background: Jordan is a country well-known for its diversity in wild plants, and for many decades, folk medicines have represented part of its cultural heritage. In the present study, investigations have been focused on the therapeutic potential of Silybum marianum and Pergularia tomentosa on type 2 diabetes mellitus. In type 2 diabetes, which is considered a global health problem, the body cannot respond to or produce insulin hormonem, which raises the blood glucose level, resulting in mortality, morbidity, healthcare expenses, and reduced life quality. Dipeptidyl peptidase-IV (DPP-IV) enzyme, a serine protease, is responsible for deactivating incretin hormones that promote insulin secretion. Accordingly, the DPP-IV inhibitory activity of these plant extracts that prolong the hypoglycemic effect of incretins was evaluated. Methods: The aerial parts of S. marianum and P. tomentosa were dried, ground, and extracted with ethanol. The ethanol extract was dried under reduced pressure and was partitioned by methanol, butanol, and hexane according to a systematic procedure. The inhibition of the DPP-IV enzyme by the different extracts was studied (at 10.0 mg/mL concentration). Sitagliptin was used as the positive control. Results: Fortunately, most of the plant extracts have noticeable inhibitory activity against the DPPIV enzyme. It was found that the tested methanol extract of S. marianum has an inhibitory activity of 75.6% and the butanol extract of P. tomentosa has an inhibitory activity of 73.6%, which are analogous to DPP-IV inhibition of sitagliptin (78.5%), the used positive inhibitor. A superior inhibition of 98.1% was displayed for the butanol extract of S. marianum at 10.0 mg/ mL concentration. Conclusion: The revealed DPP-IV inhibitory activity of tested extracts advocates that their active constituents, particularly flavonoids, are capable of binding to the enzyme’s active cleft.