Chemical constituents of the anti-liver cancer active site of Scutellaria barbata

Abstract

In previous study, the ethanol extract of Scutellaria barbata was partitioned with petroleum ether and EtOAc, respectively. The ethyl acetate extract site was subjected to column chromatography over macroporous adsorption resin eluting with gradient ethanol. The 70% ethanol elution fraction exhibited good anti-liver cancer activity. To clarify the active ingredients, the active site was separated and purified by silica gel column chromatography, Sephadex LH-20 column chromatography, preparative TLC, and semi preparative liquid chromatography, etc. Multiple spectroscopic analysis methods were used to identify the structure of the monomer compounds, and CCK-8 method was used to evaluate the inhibitory activity of all compounds on the proliferation of human liver cancer HepG2 cells in vitro. At the same time, molecular docking technology was used to investigate the binding of the most active compounds with target proteins VEGF-2 and FGFR-1, which were obtained from targeted drug for liver cancer. The results were as follows: (1) A total of 14 compounds were isolated from the active site, including 12 neo-clerodane diterpenoids and 2 flavonoids, which were identified as scuefolide C (1), 6-acetoxy-7-nicotinoyloxyscutebarbatine G (2), scutestrigillosin D (3), scutehenanine D (4), scutebarbatine A (5), scutebarbatine B (6), 7-O-nicotinoyloxyscutebarbatine H (7), scutebarbatine N (8), scutebarbatine Y (9), barbatin A (10), barbatin B (11), barbatin D (12), 5, 7, 6′- trihydroxy-2′-methoxyflavonol (13) and 5, 8-dihydroxy-6, 7-dimethoxyflavone (14). Compounds 1-3 and 13, 14 were isolated from this plant for the first time. (2) The results of cell proliferation inhibition activity test showed that compounds 4, 7, 10-12 exhibited weaker cell proliferation inhibitory activity against HepG2, and Compound 6 exhibited similar cell proliferation inhibitory activity to the positive control (cisplatin), while Compound 5 exhibited stronger cell proliferation inhibitory activity than cisplatin. (3) The molecular docking results showed that Compound 5 and Compound 6 had good binding affinity with target protein VEGF-2, which binded to residues such as GLY-841, LEU-840, ASN-923, ARG-1032 in VEGF-2 protein through hydrogen bonding. At the same time, Compound 5 and Compound 6 exhibited poor binding affinity with target protein FGFR-1. The results of this study not only enrich the chemical groups of S. barbata, but also provide a reference for further study on the mechanism of active compounds against liver cancer.

Keywords

• scutellaria barbata
• chemical constituents
• diterpenoids
• liver cancer
• cell proliferation