Antidiabetic Activities of Medicinal Plants in Traditional Recipes and Candidate Antidiabetic Compounds from Hydnophytum formicarum Jack. Tubers

Introduction: Wang-Nam-Yen hospital recipe used as a traditional antidiabetic for a long time, but its beneficial properties have not been described. Materials and Methods: Antidiabetic mechanisms including anti-α-glucosidase, anti-α-amylase, anti-dipeptidyl-peptidase-4, antioxidant, anti-inflammatory activities, and wound healing effects of 26 medicinal plants that make up the Wang-Nam-Yen preparation were investigated. Results: Interestingly, most plants in this study inhibited α-glucosidase and α-amylase at excellent levels with higher potency than standard acarbose (18.2% ± 0.5). Hydnophytum formicarum, Urceola minutiflora, and Lagerstroemia speciosa, inhibited DPP-4 with more than 70% inhibition at 50 μg/mL (82.8%± 0.8, 71.9% ± 0.3, and 71.1% ± 0.1, respectively compared with standard Diprotin A at 50 μg/mL, 90.1% ± 0.4). Terminalia arjuna showed the highest inhibition in all anti-oxidation assays. Andrographis paniculata inhibited NO production at 90.1% ± 2.4, which was more effective than indomethacin (34.3% ± 2.4). Most of the herbs contained high amounts of terpenoids and flavonoids, which might play an important role in antidiabetic activity. The results demonstrated that H. formicarum extract exhibited the highest anti-DPP-4 activity (IC50 = 33.87 ± 0.02 μg/mL). When H. formicarum ethanolic extract was isolated, Palmitic acid (1) exhibited DPP-4 inhibitory activity at IC50 value of 73.82 ± 2.64 μg/mL, and a mixture of stigmasterol (2) and ß-sitosterol (3) at 78.58 ± 0.92 μg/mL. Conclusion: Many herbs in the Wang-Nam-Yen preparation possessed properties predictive for antidiabetic treatment. The results also suggest the possibility of further use of H. formicarum and its isolated compounds as a standard diabetic drug in the future.