In Vitro Comparative Study of the Inhibitory Effects of Mangiferin and Its Aglycone Norathyriol towards UDP-Glucuronosyl Transferase (UGT) Isoforms.

Mangiferin (MGF), the predominant constituent of extracts of the mango plant Mangifera Indica L., has been investigated extensively because of its remarkable pharmacological effects. In vitro recombinant UGTs-catalyzed glucuronidation of 4-methylumbelliferone (4-MU) was used to investigate the inhibition of mangiferin and aglycone norathyriol towards various isoforms of UGTs in our study, which evaluated the inhibitory capacity of MGF and its aglycone norathyriol (NTR) towards UDP-glucuronosyltransferase (UGT) isoforms. Initial screening experiment showed that deglycosylation of MGF into NTR strongly increased the inhibitory effects towards almost all the tested UGT isoforms at a concentration of 100 µM. Kinetic experiments were performed to further characterize the inhibition of UGT1A3, UGT1A7 and UGT1A9 by NTR. NTR competitively inhibited UGT1A3, UGT1A7 and UGT1A9, with an IC50 value of 8.2, 4.4, and 12.3 µM, and a Ki value of 1.6, 2.0, and 2.8 µM, respectively. In silico docking showed that only NTR could dock into the activity cavity of UGT1A3, UGT1A7 and UGT1A9. The binding free energy of NTR to UGT1A3, 1A7, 1A9 were -7.4, -7.9 and -4.0 kcal/mol, respectively. Based on the inhibition evaluation standard ([I]/Ki < 0.1, low possibility; 0.1 < [I]/Ki < 1, medium possibility; [I]/Ki > 1, high possibility), an in vivo herb-drug interaction between MGF/NTR and drugs mainly undergoing UGT1A3-, UGT1A7- or UGT1A9-catalyzed metabolism might occur when the plasma concentration of NTR is above 1.6, 2.0 and 2.8 µM, respectively.

The Inhibition of UDP-Glucuronosyltransferase (UGT) Isoforms by Praeruptorin A and B.

Praeruptorin A (PA) and B (PB) are two important compounds isolated from Bai-hua Qian-hu and have been reported to exert multiple biochemical and pharmacological activities. The present study aims to determine the inhibition of PA and PB on the activity of important phase II drug-metabolizing enzymes uridine 5'-diphospho-glucuronosyltransferase (UGTs) isoforms. In vitro UGT incubation system was used to determine the inhibition potential of PA and PB on the activity of various UGT isoforms. In silico docking was performed to explain the inhibition difference between PA and PB towards the activity of UGT1A6. Inhibition behaviour was determined, and in vitro-in vivo extrapolation was performed by using the combination of in vitro inhibition kinetic parameter (Ki ) and in vivo exposure level of PA. Praeruptorin A (100 µM) exhibited the strongest inhibition on the activity of UGT1A6 and UGT2B7, with 97.8% and 90.1% activity inhibited by 100 µM of PA, respectively. In silico docking study indicates the significant contribution of hydrogen bond interaction towards the stronger inhibition of PA than PB towards UGT1A6. Praeruptorin A noncompetitively inhibited the activity of UGT1A6 and competitively inhibited the activity of UGT2B7. The inhibition kinetic parameter (Ki ) of PA towards UGT1A6 and UGT2B7 was calculated to be 1.2 and 3.3 µM, respectively. The [I]/Ki value was calculated to be 15.8 and 5.8 for the inhibition of PA on UGT1A6 and UGT2B7, indicating high inhibition potential of PA towards these two UGT isoforms in vivo. Therefore, closely monitoring the interaction between PA and drugs mainly undergoing UGT1A6 or UGT2B7-catalyzed metabolism is very necessary. Copyright © 2016 John Wiley & Sons, Ltd.

Comparative anti-inflammatory characterization of wild fruiting body, liquid-state fermentation, and solid-state culture of Taiwanofungus camphoratus in microglia and the mechanism of its action.

Taiwanofungus camphoratus (syn. Antrodia camphorata), a medicinal mushroom in Taiwan, is reputed to provide several therapeutic benefits, but the wild fruiting body is very rare. In this study, we used Taiwanofungus camphoratus extracts from wild fruiting bodies and two types of artificial cultivation (solid-state culture and liquid-state fermentation) to examine their anti-inflammatory effects in microglia cells and their possible roles in protection against neurodegenerative diseases. First, EOC13.31 microglia was treated with various kinds of Taiwanofungus camphoratus extracts and lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) to evaluate the iNOS expression. Western blot and RT-PCR analysis showed that among the various kinds of extracts from wild fruiting bodies, methanol extracts were the most potent inhibitors of iNOS expression. Secondly, the potency of methanol extracts could be ranked as follows: extracts of wild fruiting body>solid-state culture>liquid-state fermentation. To clarify the mechanisms involved, methanol extracts from fruiting body were found to inhibit the phosphorylation of extracellular signal-regulated protein kinases (ERK), c-Jun NH2-terminal protein kinases (JNK) and signal transducer and activator of transcription-1 (STAT-1) induced by LPS/IFN-gamma. Methanol extracts from fruiting body also inhibited NF-kappaB activation through the prevention of inhibitor kappaB (IkappaB) degradation. Moreover, methanol extracts from wild fruiting body inhibited both the iNOS and cyclooxygenase-2 (COX-2) expression induced by beta-amyloid in microglia in a dose-dependent manner. In an animal model, we confirmed that methanol extracts from fruiting bodies were able to suppress ear edema, indicating that they have anti-inflammatory activity in vivo. These results suggest that Taiwanofungus camphoratus exhibits an anti-inflammatory activity that might contribute to the prevention of neurodegenerative diseases.