Exploration of antidiabetic and antioxidant properties of fresh and freeze-dried Hellenia speciosa , Coccinia grandis and Gymnema sylvestre leaves

The drying method can have an impact on the stability and composition of bioactive compounds in plant materials, as well as their therapeutic activities. This study aimed at evaluating the anti-glycation and antioxidant properties of freeze-dried and fresh leaves of selected ayurvedic medicinal plants. Fresh and freeze-dried leaves of Hellenia speciosa, Gymnema sylvestre and Coccinia grandis were extracted separately with 95% ethanol. The extracts were studied for their anti-glucosidase, antiglycation, glycation-reversing activities and uptake of glucose by yeast cells. Antioxidant activities of extracts were evaluated using ABTS and DPPH free radical scavenging activities. All extracts of the freeze-dried leaves showed significant ( P  < 0.05) anti-glucosidase, antiglycation, and glycation-reversing activities than the fresh leaves of the same species. The freeze-dried leaf extract of H. speciosa demonstrated the highest antiglycation, anti-glucosidase, and glycation reversing activities among the plant species, with IC50 values of 100.76 ± 5.99 µg/ml, 28.11 ± 1.30 µg/ml and EC50 values of 147.24 ± 3.86 µg/ml, respectively. In addition to that, freeze-dried H. speciosa showed the maximum ABTS and DPPH free radical scavenging activity. This study confirmed that freeze-dried leaves have promising anti-diabetic and antioxidant properties that can be used to develop herbal nutritional supplements or functional foods for diabetes mellitus treatment.