Chemical characterization and quantitative determination of flavonoids and phenolic acids in yerba santa (Eriodictyon spp.) using UHPLC/DAD/Q-ToF.

Eriodictyon species, commonly known as yerba santa, are plants native to the Southwestern United States and northern Mexico. The plants are known for their medicinal properties and have been used by indigenous people for centuries to treat various ailments, in particular, respiratory conditions. Despite a long history of traditional use, many of the species have never been fully chemically characterized, and the constituent range of the species has not been comprehensively reported. In an effort to establish a quality control and chemical characterization method, an extensive set of Eriodictyon species samples including E. californicum (n = 85), E. angustifolium (n = 8), E. trichocalyx (n = 5), E. crassifolium (n = 9), E. tomentosum (n = 2), E. traskiae (n = 1), and E. capitatum (n = 1) were investigated. Fourteen compounds comprised of flavonoids and phenolic acids were quantified utilizing an UHPLC/DAD method. The results from the method validation demonstrated excellent linearity (R > 0.99) and sensitivity as evidenced by LOD (0.01-0.1 µg/mL) and LOQ (0.05-0.2 µg/mL). Likewise, the method was found to be precise (RSD < 2.78%) with recoveries between 88.9% and 103.2%. Furthermore, by using UHPLC/ESI/Q-ToF data and protonated, deprotonated, and adduct and fragment ions in positive and negative ion modes, we were able to identify 53 compounds in yerba santa plant samples. To the best of our knowledge, this work encapsulates the most comprehensive data set currently available for the chemical characterization and quantification of the primary constituents in Eriodictyon species. Additionally, results of this study also demonstrated the applicability of the developed method for quality assessment of raw material and commercial herbal products containing different Eriodictyon species.