Rapid Detection of Adulteration in Boswellia Extracts with Citric Acid by UPLC–HRMS and ¹H NMR

Abstract

Boswellia serrata ole-gum-resin extracts (BSEs) are commonly used as food supplements, especially in osteoarthritis management. The quality standard is established by determining 11-keto-β-boswellic acid (KBA) and acetyl-11-keto-boswellic acid (AKBA) content using high-performance liquid chromatography (HPLC) or assessing the total boswellic acid (TBA) content by titrimetry. The limited geographical distribution of Boswellia species and increasing industrial demand could increase the risk of adulteration in Boswellia-containing products. In this study, 14 BSEs from commercial sources, used in food supplements, were analyzed in comparison with a USP Reference Standard extract. The KBA and AKBA content was determined by HPLC, whereas the TBA content was determined by titration. Targeted UHPLC-high-resolution mass spectrometry (HRMS) was applied to identify the carboxylic acid content in the samples. The ¹H NMR spectra of extracts were also analyzed. Only two products met the criteria for KBA and AKBA content. Although, the TBA content complied with the expected amount, 10 extracts contained citric acid levels of 6–11% even though citric acid is not a cha­racteristic component of BSEs. Our results suggest undeclared addition of citric acid to comply with declared contents of TBA when using titration methods. Incorporation of citric acid to industrial samples – in order to alter the outcomes of the titration analysis – was demonstrated for the first time.

Keywords:

• Adulteration
• Boswellia
• citric acid
• food supplement
• frankincense
• total boswellic acid content

Disclosure statement

The authors declare no conflicts of interest. The authors alone are responsible for the content and writing of the article.

Data availability statement

Data are available for research purpose upon reasonable request to the corresponding author.

Additional information

Funding

This research was funded by Hungarian Ministry of Culture and Innovation National Talent Program NTP-NFTÖ-22-B-0203. Project no. TKP2021-EGA-32 has been implemented with the support provided by the Ministry of Innovation and Technology of Hungary from the National Research, Development and Innovation Fund, financed under the TKP2021-EGA Funding Scheme. This work was also supported by National Research, Development, and Innovation Office-NKFIA through projects: National Laboratory of Translational Neuroscience (NLTN) "Neurodevelopmental disorders" "Adult nervous system disorders" (RRF-2.3.1-21-2022-00011).

Notes on contributors

Péter Püski

Péter Püski holds PharmD and is a PhD student at Institute of Pharmacognosy (University of Szeged, Faculty of Pharmacy). His research interests are phytochemistry and analytics of dietary supplements.

Tímea Körmöczi

Tímea Körmöczi is a researcher at Institute of Pharmaceutical Analysis (University of Szeged, Faculty of Pharmacy). Her research fields are liquid chromatography, mass spectroscopy, and metabolomics.

Róbert Berkecz

Róbert Berkecz holds PhD and he is an associate professor at Institute of Pharmaceutical Analysis (University of Szeged, Faculty of Pharmacy). He is the author of 70+ papers in field of analytics.

Anita Barta

Anita Barta obtained her PharmD and is in the final stage of her PhD at University of Szeged. Her research field is preparative phytochemistry and NMR spectroscopy of plant secondary metabolites.

Ákos Bajtel

Ákos Bajtel PharmD is a clinical pharmacist and researcher at University of Szeged. He is working on completion of his PhD thesis.

Tivadar Kiss

Tivadar Kiss holds PhD in pharmacognosy. He is an assistant professor at Institute of Pharmacognosy (University of Szeged, Faculty of Pharmacy). His research interests include phytochemistry, analytics of dietary supplements and science education.