LC-MS/MS analysis and α-glucosidase inhibitory effect of majonoside R2 in Vietnamese ginseng (Panax vietnamensis Ha & Grushv.)

Majonoside R2 (MR2), the principal saponin of Vietnamese ginseng (Panax vietnamensis Ha & Grushv.), has the unique structure of ocotillol-type dammarane and showed remarkable biological activities. This paper deals with the new findings in the chemical analysis MR2 by the tandem LC-MS/MS and, especially, its inhibitory activities on α-glucosidase for diabetic management. The developed LC-MS/MS method revealed advantages of high selectivity with specific mass transition from precursor [M + H]⁺ ion (m/z 784.4) into product ion (m/z 475.1), high sensitivity (calibration range: 5-250 ppb; LOD: 1.5 ppb; LOQ: 5.0 ppb), and high accuracy to support further pharmaceutical analysis of MR2. MR2 and its aglycone ocotillol relatively showed certain inhibitory effects on α-glucosidase in vitro with the IC₅₀ values of 353.05 and 219.64 µg/mL and supported by molecular docking analysis, in which MR2 and ocotillol could play as allosteric inhibitors with high binding affinity (-7.8 and -8.1 kcal/mol) evidenced by bonding interactions.