| Danshen, the dried root and rhizome of Salvia miltiorrhiza Bg. (Fam. Labiatae), is a widely used medicinal plant for the treatment of cardiovascular diseases in China and also a complementary medicine in the West. In this study, six water-extracts of Danshen obtained from heat reflux water extraction and microwave-assisted extraction with water (MAE-W) at different temperatures were prepared for evaluation of their composition and pharmacological effects such as antioxidant, anti-apoptosis and vascular relaxation. Among these extracts obtained, the third-round MAE-W (100 °C) product, which was the last round product obtained by extracting the same crude material three times, had the highest contents of phenolic acids and tanshinones, with the strongest antioxidant activity estimated by 2, 2-diphenyl-1-(2, 4, 6-trinitrophenyl) hydrazyl (DPPH) assay and ferric reducing / antioxidant potential (FRAP) assay. This extract also possessed the strongest inhibitory effects on 2, 2'-azobis-2-amidino-propane (AAPH)-induced haemolysis in human red blood cells, hydrogen peroxide-induced apoptosis in rat heart H9c2 cells and the highest relaxation effects on rat basilar artery. The antioxidant effects of Danshen water-extracts linearly correlated to their relaxation effects (r = 0.895 to 0.977). Through multiple linear regression analysis, danshensu was found to be the most significant marker in the antioxidant and vasodilation effects of Danshen water-extract, while tanshinone IIA as the marker on hydrogen peroxide-induced apoptosis in rat heart H9c2 cells. Danshensu is, therefore, a useful marker for the quality control of Danshen water-extracts in antioxidant and vasodilation, while tanshinone IIA for anti-apoptotic potential of water-extracts.;Tanshinones, the major lipid-soluble components isolated from Danshen, have been reported for their anti-cancer potential in various cell lines and tumor-bearing mice models. This study evaluated the apoptotic effect of miltirone and the underlying mechanisms in a human hepatoma HepG2 cell line and its p-glycoprotein (P-gp)-overexpressed doxorubicin-resistant counterpart (R-HepG2). Miltirone showed similar cytotoxicity in HepG2 (EC50 = 7.06 µM) and R-HepG2 (EC50 = 12.0 µM), demonstrated synergistic effects (1.56 - 6.25 µM) with doxorubicin (DOX) on the growth inhibition of R-HepG2 (synergism: 0.3 < CI < 0.5 at 50 % inhibition). Flow cytometric analysis showed that miltirone decreased P-gp-mediated DOX efflux in R-HepG2, and molecular docking studies illustrated that this effect was through inhibition on the active site of P-gp. At non-necrotic concentrations (25 µM or below), miltirone activated caspase-dependent apoptotic pathways, and induced the generation of reactive oxygen species (ROS) and oxidative stress which triggered ROS-mediated MAPK signaling pathways, including p38 MAPK, stress-activated protein kinase / c-Jun N-terminal kinase (SAPK/JNK) and extracellular regulated kinase 1/2, in both HepG2 and R-HepG2 cells. It is therefore concluded that miltirone is a dual inhibitor on P-gp and cell proliferation in R-HepG2 cells, with potential for the treatment of human hepatocellular carcinoma (HCC).;In order to improve the successful rates in drug development, the in vivo metabolic parameters of new chemical entities (NCEs), such as protein bindings, clearance rate, pharmacokinetic parameters and metabolism-based drug-drug interactions, should be considered at the early stage of drug discovery. Previous studies have shown that major tanshinones isolated from Danshen inhibited the metabolism of model probe substrates of human and rat CYP450 enzymes, with potential in causing herb-drug interactions. The aim of this study was to study the effect of miltirone on the metabolism of model probe substrates of CYP1A2, 2C9, 2D6 and 3A4 in pooled human liver microsomes. Miltirone showed moderate inhibition on CYP1A2 (IC50 = 1.73 µM) and CYP2C9 (IC50 = 8.61 µM), and weak inhibition on CYP2D6 (IC 50 = 30.20 µM) and CYP3A4 (IC50 = 33.88 µM). Enzyme kinetic studies showed that miltirone competitively inhibited CYP2C9 (Ki = 1.48 µM), and displayed mixed type inhibitions on CYP1A2, CYP2D6 and CYP3A4 with Ki values of 3.17 µM, 24.25 µM and 35.09 µM, respectively. Molecular docking study further confirmed the ligand-binding conformations of miltirone in the active sites of human CYP450 isoforms. These findings suggested that miltirone may have potential drug-drug interactions with CYP1A2- and CYP2C9-metabolized drugs, and to a lesser extent with CYP2D6- and CYP3A4-metabolized drugs. (Abstract shortened by UMI.). |
