Analysis of boswellic acids in dietary supplements containing Indian frankincense (Boswellia serrata) by Supercritical Fluid Chromatography.

Boswellic acids, a class of triterpenes, are the bioactive constituents in Indian frankincense, an herbal drug with pronounced anti-inflammatory activity. In this study their separation and quantification in B. serrata extracts is reported for the first time by using Supercritical Fluid Chromatography. Under optimized conditions, i.e. a Viridis HSS C18 SB column and carbon dioxide, methanol, acetonitrile and ammonium hydroxide as mobile phase, six boswellic acids could be separated in under 6 min. The assay fulfilled all validation criteria with coefficients of determination higher than 0.999, a wide linear range (30-1000 μg/mL), recovery rates from 97.1-103.0 %, excellent precision, and detection limits typical for SFC with UV-detection (≤ 5.5 μg/mL). The method could easily be hyphenated to mass spectrometry, which was helpful to tentatively assign further compounds (mainly derivatives of tirucallic acid) and to increase the assay's sensitivity. Its practical applicability was confirmed by analyzing several commercial products, which mainly contained β-boswellic acid as dominant triterpene, yet in extremely variable amounts ranging from 0.9 to 16.9 %.