α-Glucosidase enzyme inhibitory effects and ursolic and oleanolic acid contents of fourteen Anatolian Salvia species

During the last decade, ursolic and oleanolic acids have been of considerable interest because of their α-glucosidase inhibitory activities and potential effects for treatment of type 2 diabetes. A simple and sensitive reversed-phase HPLC method was developed for the simultaneous determination of ursolic acid and oleanolic acid. The optimal mobile phase was selected as 85% acetonitrile solution. The limit of detection of the method for ursolic acid and oleanolic acid were 14 ng mL⁻¹ and 13 ng mL⁻¹, respectively. The method showed good precision and accuracy with intra-day and inter-day variations of 0.54% and 7.33% for ursolic acid, intra-day and inter-day variations of 0.51% and 5.26% for oleanolic acid, and overall recoveries of 97.8% and 98.5% for ursolic acid and oleanolic acid, respectively. Application of the method to determine the ursolic acid and oleanolic acid contents in the Salvia species revealed both compounds, with varying amounts between 0.21–9.76 mg g⁻¹ ursolic acid and 0.20–12.7 mg g⁻¹ oleanolic acid, respectively, among 14 Salvia species analyzed. Additionally, the plant extracts were analyzed for their inhibitory activities on α-glucosidase. According to the results of this assay, the extracts showed considerable activity on α-glucosidase with IC₅₀ values from 17.6 to 173 μg mL⁻¹. A strong negative correlation was detected between the amounts of both acids and IC₅₀ values of extracts. Anatolian Salvia species have great potential as functional plants in the management of diabetes.