Abstract
Scutellaria baicalensis is a well-studied medicinal plant belonging to the Lamiaceae family, prized for the unique 4'-deoxyflavones produced in its roots. In this study, three native species to the Americas, S. lateriflora, S. arenicola, and S. integrifolia were identified by DNA barcoding, and phylogenetic relationships were established with other economically important Lamiaceae members. Furthermore, flavone profiles of native species were explored. 4'-deoxyflavones including baicalein, baicalin, wogonin, wogonoside, chrysin and 4'-hydroxyflavones, scutellarein, scutellarin, and apigenin, were quantified from leaves, stems, and roots. Qualitative, and quantitative differences were identified in their flavone profiles along with characteristic tissue-specific accumulation. 4'-deoxyflavones accumulated in relatively high concentrations in root tissues compared to aerial tissues in all species except S. lateriflora. Baicalin, the most abundant 4'-deoxyflavone detected, was localized in the roots of S. baicalensis and leaves of S. lateriflora, indicating differential accumulation patterns between the species. S. arenicola and S. integrifolia are phylogenetically closely related with similar flavone profiles and distribution patterns. Additionally, the S. arenicola leaf flavone profile was dominated by two major unknown peaks, identified using LC-MS/MS to most likely be luteolin-7-O-glucuronide and 5,7,2'-trihydroxy-6-methoxyflavone 7-O-glucuronide. Collectively, results presented in this study suggest an evolutionary divergence of flavonoid metabolic pathway in the Scutellaria genus of Lamiaceae.