Quantitative determination of potent α-glucosidase inhibitors, salacinol and kotalanol, in Salacia species using liquid chromatography–mass spectrometry

A practical HPLC–MS method for the quantitative determination of salacinol (1) and kotalanol (2), potent α-glucosidase inhibitors from Salacia species (Hippocrateaceae) as a specific remedy for diabetes in Ayurvedic system, was developed. The optimum conditions of separation and detection of these two constituents were achieved on a Asahipak NH2P-50 column (5 μm particle size, 2.0 mm i.d. × 150 mm) with a CH3CN–H2O mobile phase, associated with MS using electrospray ionization source. The overall recoveries of 1 (85.8–112.6%) and 2 (99.7–106.1%), and relative standard deviation values of intra- and inter-day precision were lower than 6.8 and 8.5%, respectively. The detection (S/N = 3) and quantitation limits (S/N = 10) were established to be 0.015 and 0.050 ng for 1, and 0.030 and 0.10 ng for 2, respectively. The correlation coefficients of all the calibration curves showed good linearity within test ranges. The extraction process was also optimized as 2 h immersion in water under reflux. The method was applied to evaluate extracts of three kinds of Salacia species, i.e. S. reticulata, S. oblonga, and S. chinensis, and those of four different parts, i.e. roots, stems, leaves and fruits of the same material, revealing that the extract from the roots of S. reticulata had the highest contents of these compounds. The results indicated that the assay was reproducible and precise and could be readily utilized for the evaluation of Salacia species.