Anti-Hyperglycemic Effects of Thai Herbal Medicines

This study aims to investigate selected medicinal plants' anti-oxidative and antihyperglycemic activities to develop an effective remedy for lowering blood glucose levels and/or reducing diabetes complications. Thai medicinal plants, reported to have blood sugar-lowering effects, were selected for the study: <i>Coccinia grandis</i>, <i>Gymnema inodorum</i>, <i>Gynostemma pentaphyllum</i>, <i>Hibiscus sabdariffa</i>, <i>Momordica charantia</i>, <i>Morus alba</i>, and <i>Zingiber officinale</i>. Each species was extracted by Soxhlet's extraction using ethanol as solvent. The ethanolic crude extract of each species was then evaluated for its phytochemicals, anti-oxidant, and antihyperglycemic activities. The results showed that the extract of <i>Z. officinale</i> gave the highest values of total phenolic and total flavonoid content (167.95 mg gallic acid equivalents (GAE)/g and 81.70 mg CE/g, respectively). Anti-oxidant activity was determined using DPPH and ABTS radical scavenging activity. Among the ethanolic extracts, <i>Z. officinale</i> exhibited the highest anti-oxidant activity with IC₅₀ values of 19.16 and 8.53 µg/mL, respectively. The antihyperglycemic activity was assessed using α-glucosidase inhibitory and glucose consumption activities. <i>M. alba</i> and <i>G. pentaphyllum</i> demonstrated the highest α-glucosidase inhibitory activity among the ethanolic extracts, with IC₅₀ values of 134.40 and 329.97 µg/mL, respectively. <i>Z. officinale</i> and <i>H. sabdariffa</i> showed the highest percentage of glucose consumption activity in induced insulin-resistant HepG2 cells at a concentration of 50 µg/mL with 145.16 and 107.03%, respectively. The results from α-glucosidase inhibitory and glucose consumption activities were developed as an effective antihyperglycemic remedy. Among the remedies tested, the R1 remedy exhibited the highest potential for reducing blood glucose levels, with an IC₅₀ value of 122.10 µg/mL. Therefore, the R1 remedy should be further studied for its effects on animals.