Simultaneous determination of 15 flavonoids from different parts of Scutellaria baicalensis and its chemometrics analysis

Objective The aerial parts of Scutellaria baicalensis were used as Huangqin Tea for thousands of years and mainly contain flavonoids which contribute to its bioactivities. However, there is no appropriate quality evaluation method of Huangqin Tea, and three flavanones of isocarthamidin-7-O-β-D-glucuronide, carthamidin-7-O-β-D-glucuronide, and isoscutellarein-8-O-β-D-glucuronide with high contents in the aerial parts have never been defined quantitatively. Here, an HPLC-DAD method for simultaneous determination of 15 flavonoids and systematically compared their contents and distribution in the roots, stems, leaves, and flowers of S. baicalensis was established. Methods Under the HPLC-DAD chromatographic conditions, 77 batches of samples of S. baicalensis were analyzed. Meanwhile, the chromatographic fingerprint of different parts of S. baicalensis was established. Subsequently, principal component analysis (PCA), orthogonal projections to latent structures discriminant analysis (OPLS-DA), and clustering heat map were performed based on the contents of 15 flavonoids in different parts of S. baicalensis. Results The results showed significant differences in the contents and distributions of 15 flavonoids among the different parts of S. baicalensis. The chemical composition of stems showed some similarities to leaves, and their contents were all lower than leaves. The contents of isocarthamidin-7-O-β–glucuronide [(106.66 66 ± 22.68) mg/g], carthamidin-7-O-β-D-glucuronide [(19.82 ± 11.17) mg/g], and isoscutellarein-8-O-β-D-glucuronide [(3.10 ± 1.73) mg/g] were the highest in leaves. The content of apigenin-7-O-β-D-glucopyranoside and chrysin-7-O-β-D-glucuronide were the highest in flowers. The contents of baicalin, baicalein, wogonoside, wogonin, alpinetin, and oroxylin A were higher in roots than in other parts. Conclusion The method was fully validated and could be effectively used to characterize the contents and distributions of main flavonoids in the different parts of S. baicalensis. It may lay a foundation to establish the quality evaluation system for Huangqin Tea.