Tracing analgesic constituents from crude and vinegar-processed resin of Boswellia carterii by integrating ultra-performance liquid chromatography tandem mass spectrometry-based determination, analgesic evaluation in mice, and gray relationship analysis.

The analgesic effect of the resin of Boswellia carterii (BC) is well known; however, the constituents that contribute to the analgesic effect remain elusive. The current study integrates ultrasonic-assisted extraction, quantitative determination, analgesic evaluation in rats, and gray relationship analysis for tracing analgesic constituents from the resin of BC. First, a robust and precise ultra-performance liquid chromatography tandem mass spectrometry approach with multiple reaction monitoring mode was developed for the simultaneous quantification of seven major constituents in crude and vinegar-processed resin of BC. Glycyrrhetinic acid was chosen as the internal standard. The approach showed good linearity. The intra- and inter-day precisions of each constituent were within 3.0%. The recoveries of each constituent were in the range of 96.4-102.7%. The approach was then applied to determine the seven constituents in 10 batches of crude and vinegar-processed resin of BC. Second, the analgesic effects of crude and vinegar-processed resin of BC were assessed in mice. Third, chemometrics methods, gray relationship analysis, and partial least squares regression were employed for determining the relationship between the contents of seven constituents and their analgesic effects. 11-Keto-β-boswellic acid, 3-acetyl-β-boswellic acid, 3-acetyl-α-boswellic acid, 3-acetyl-11-keto-β-boswellic acid, and β-sitosterol were identified as the key analgesic constituents of BC.