Correlation Between Boswellic and Lupeolic Acid Contents in Dietary Supplements and Their In Vitro Cytotoxic and Anti-inflammatory Activities

Reviewed: Schmiech M, Lang SJ, Ulrich J, Werner K, Rashan LJ, Syrovets T, Simmet T. UHPLC‐Comparative investigation of frankincense nutraceuticals: Correlation of boswellic and lupeolic acid contents with cytokine release inhibition and toxicity against triple-negative breast cancer cells. Nutrients. 2019;11(10): pii:E2341.

Keywords: Adulteration, anti-inflammatory, Boswellia sacra, Boswellia serrata, boswellic acids, cytotoxicity, Indian frankincense, HPLC-MS/MS

For this investigation, the contents of six boswellic acids (α-boswellic acid, 3-O-acetyl-α-boswellic acid, β-boswellic acid, 3-O-acetyl-β-boswellic acid, 11-keto-β-boswellic acid, 3-O-acetyl-11-keto-β-boswellic acid),3-O-acetyl-lupeolic acid,and lupeolic acid were determined in 16 frankincense dietary supplements by high-performance liquid chromatography with tandem mass spectrometric detection (HPLC-MS/MS). The samples were obtained directly from the manufacturer or from pharmacies in Germany (n = 8), Austria (n = 2), the Netherlands (n = 2), India, Liechtenstein, England, and the USA.

Quantitative data were obtained by multiple-reaction monitoring (MSM) mass spectrometry using external standards for calibration. The method was validated in a previous study, in which the authors had analyzed the triterpene contents in 40 samples of crude oleogum resin from eight different Boswellia species.¹ The quantitative data were further evaluated using multivariate statistics using principal component analysis (PCA) and hierarchical agglomerative clustering (HAC).

Based on a comparison with data from authentic samples, the authors concluded that two samples labeled to contain B. sacra and B. carterii were likely composed of Indian frankincense (B. serrata) resin. Two samples contained very low amounts of triterpenes, making up 2.9% and 0.4%, respectively, of the total sample weight. The latter product, purchased from Vitabay, an online seller in the Netherlands, was labeled to contain 400 mg of B. serrata extract, but either has a very low amount of Indian frankincense, or is composed of a low triterpene-containing frankincense species, e.g., B. frereana. 

The results from the in vitro bioactivity assays suggest that the contents in 3-O-acetyl-β-boswellic acid was most highly correlated to inhibition of TNF-α, IL-6, and IL-8 cytokine release, as well as cytotoxicity against breast cancer cells. Dietary supplements with total boswellic and lupeolic acid contents over 30%, and/or 3-O-acetyl-β-boswellic acid contents over 36 mg/g significantly inhibited the expression of the proinflammatory cytokines TNF-α, IL-6, and IL-8, and thus are considered the most potent anti-inflammatory products among those that were evaluated.

Comment: Compared to the paper by Miscioscia et al.,² this evaluation of the quality and composition of Boswellia supplements is more robust because of the use of mass spectrometric data to confirm peak identity. The inclusion of eight triterpenes in the quantification allows a better assessment of the identity of the species from which the gum resin was obtained. The extensive previous work on species distinction by these authors¹ certainly helped in the assessment of the results. The data confirm the high variability of the quality of Boswellia dietary supplements on the markets, and the occurrence of adulteration in a small number of products. Also, the results from the dietary supplement analysis may indicate a change in the adulteration landscape. While previous studies mainly raised concerns of B. serrata adulteration, the new data imply that the supply from certain Boswellia species (B. sacra, B. carterii) growing in Northeast Africa and on the Arab peninsula may be dwindling, and that oleogum resin from these species, which have been used as adulterants of B. serrata in the past,⁵ may now be at risk of being substituted with Indian frankincense.

Particularly interesting is the outcome of the bioassay work: While many researchers have focused on the 5-lipoxygenase inhibitory properties of 3-O-acetyl-11-keto-β-boswellic acid as an explanation of the plants benefits,^3,4 this study suggests that some of the other triterpenes are important for the anti-inflammatory effects of Indian frankincense as well.

References

1. Schmiech M, Lang SJ, Werner K, Rashan LJ, Syrovets T, Simmet T. Comparative analysis of pentacyclic triterpenic acid compositions in oleogum resins of different Boswellia species and their In vitro cytotoxicity against treatment-resistant human breast cancer cells. Molecules. 2019;24:2153.
2. Miscioscia E, Shmalberg J, Scott KC. Measurement of 3-acetyl-11-keto-beta-boswellic acid and 11-keto-beta-boswellic acid in Boswellia serrata supplements administered to dogs. BMC Vet Res. 2019;15:270.
3. Sailer ER, Subramanian LR, Rall B, Hoernlein RF, Ammon HPT, Safayhi H. Acetyl 11-keto-β-boswellic acid: Structural requirements for binding and 5-lipoxygenase inhibitory activity. Brit J Pharmacol. 1996;117:615-618.
4. Safayhi H, Sailer ER, Ammon HPT. Mechanism of 5-lipoxygenase inhibition by acetyl-11-keto-β-boswellic acid. Mol Pharmacol. 1995;47:1212-1216.
5. McCutcheon A. Boswellia serrata adulteration. Botanical Adulterants Prevention Bulletin. Austin, TX: ABC-AHP-NCNPR Botanical Adulterants Prevention Program. 2018:1-7.