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. 2020 Nov 16;117(48):30816–30823. doi: 10.1073/pnas.2012745117

Fig. 1.

Fig. 1.

The biosynthetic pathway for (iso)schaftosides in S. baicalensis and functional characterization of SbCGTa and SbCGTb. (A) The structures of schaftoside (4a, apigenin 6-C-β-d-glucoside-8-C-α-l-arabinopyranoside) and isoschaftoside (4b, apigenin 6-C-α-l-arabinopyranoside-8-C-β-d-glucoside). (B) Pictures of the S. baicalensis plant and the Chinese herbal medicine Huang-Qin. (C) High-performance liquid chromatography (HPLC) chromatograms for functional characterization of SbCGTa and SbCGTb with 2 and 3 as substrates. (D) Mass spectra and tandem mass spectrometry (MS/MS) fragmentations of 3 and 4. (E) A proposed biosynthetic pathway for schaftoside and isoschaftoside. ∇, the products were purified in this study and identified by NMR; Δ, the products were identified by comparing with reference standards; *, the NMR spectral data were reported in this work. The 1, naringenin; 2, 2-hydroxynaringenin; 3, 2-hydroxynaringenin mono-C-glucoside; 3a, isovitexin; 3b, vitexin; 4, 2-hydroxynaringenin 6,8-di-C-glucoside-arabinoside. Glc, glucosyl residue; Ara, arabinosyl residue.