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Sanguinarine (SAG) is the most abundant constituent of Macleaya cordata (Willd.) R. Br. (Popaceae). SAG has shown antimammary and colorectal metastatic effects in mice in vivo, suggesting its potential for cancer chemotherapy. To determine the antimetastatic effect and underlying molecular mechanisms of SAG on melanoma. CCK8 assay was used to determine the inhibition of SAG on the proliferation of A375 and A2058 cells. Network pharmacology analysis was applied to construct a compound-target network and select potential therapeutic targets of SAG against melanoma. Molecular docking simulation was conducted for further analysis of the selected targets. In vitro migration/invasion/western blot assay with 1, 1.5, 2 μM SAG and in vivo effect of 2, 4, 8 mg/kg SAG in xenotransplantation model in nude mice. The key targets of SAG treatment for melanoma were mainly enriched in PI3K-AKT pathway, and the binding energy of SAG to PI3K, AKT, and mTOR were −6.33, −6.31, and −6.07 kcal/mol, respectively. SAG treatment inhibited the proliferation, migration, and invasion ability of A375 and A2058 cells (p < 0.05) with IC50 values of 2.378 μM and 2.719 μM, respectively. It also decreased the phosphorylation levels of FAK, PI3K, AKT, mTOR and protein expression levels of MMP2 and ICAM-2. In the nude mouse xenograft model, 2, 4, 8 mg/kg SAG was shown to be effective in inhibiting tumour growth. Our research offered a theoretical foundation for the clinical antitumor properties of SAG, further suggesting its potential application in the clinic. [ABSTRACT FROM AUTHOR]

Compared with coumarin, 7-hydroxycoumarin could serve as a better hit for developing CYP2A6 inhibitors. In this study, a series of 7-hydroxycoumarin and its structural analogues were collected to study their structure-activity relationship (SAR) and isoform selectivity for inhibiting CYP2A6. All tested coumarins except a C4 phenyl derivative (11) showed higher inhibitory activities for CYP2A6 over the other CYP isoforms, including CYP1A2, CYP2D6, CYP2E1, CYP3A4, CYP2C8, and CYP2C9. Of these coumarins, 6,7-dihydroxycoumarin (1) and 7,8-dihydroxycoumarin (9) were found to be potent inhibitors of CYP2A6 with IC 50 / K i value of 0.39/0.25 and 4.61/3.02 μM, respectively, compared to methoxalen as positive control (IC 50 / K i = 0.43/0.26 μM). In contrast, other coumarins showed low or decreased CYP2A6-inhibiting activities. SAR analysis showed that hydroxy groups might be important for CYP2A6 inhibition, and the rank order of sites for hydroxy substitution was C6 > C7 > C8. In addition, either hydrophobic or hydrophilic substituents introduced into C4, C6 and C8 led to a reduction in CYP2A6-inhibiting activity, and the degree of influence was dependent on the size and electrical charge of substituents. Furthermore, inhibition kinetic analysis and docking simulations demonstrated that the 8- O -glucosylated coumarin derivative (17) exhibited noncompetitive inhibition against CYP2A6, while competitive inhibition patterns were noted for the other tested coumarins. The mechanisms underlying the inhibitors binding to CYP2A6 were further investigated by molecular docking study. The findings presented herein are very helpful for developing highly selective and more potent CYP2A6 inhibitors. Unlabelled Image [ABSTRACT FROM AUTHOR]

The differences in catalytic mechanism and domain between the soluble (S-COMT) and membrane-bound catechol- O -methyltransferase (MB-COMT) are poorly documented due to the unavailable crystal structure of MB-COMT. Considering the enzymatic nature of S-COMT and MB-COMT, the challenge could be solvable by probing the interactions between the enzymes with the ligands with minor differences in structures. Herein, isomeric shikonin and alkannin bearing a R/S -OH group in side chain at the C2 position were used for domain profiling of COMTs. Human and rat liver-derived COMTs showed the differences in inhibitory response (human's IC 50 and K i values for S-COMT < rat's, 5.80–19.56 vs. 19.56–37.47 μM; human's IC 50 and K i values for MB-COMT > rat's) and mechanism (uncompetition vs. noncompetition) towards the two isomers. The inhibition of the two isomers against human and rat S-COMTs was stronger than those for MB-COMTs (S-COMT's IC 50 and K i values < MB-COMT's, 5.80–37.47 vs. 40.01–111.8 μM). Additionally, the inhibition response of alkannin was higher than those of shikonin in no matter human and rat COMTs. Molecular docking stimulation was used for analysis. The inhibitory effects observed in in vitro and in silico tests were confirmed in vivo. These findings would facilitate further COMT-associated basic and applied research. [Display omitted] • The catalytic mechanism and domain of S-COMT and MB-COMT were probed using isomeric shikonin and alkannin. • S-COMT is more subject to inhibition by shikonin and alkannin compared with MB-COMT. • Alkannin has a higher inhibitory potency towards COMTs than that of shikonin. • The tendency mentioned above was investigated using inhibition kinetics and molecular docking, and further validated in vivo. • Species difference in inhibiting human and rat COMTs by shikonin and alkannin was studied and discussed mechanistically. [ABSTRACT FROM AUTHOR]