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Aristolochic acids (AAs) are naturally occurring nitro phenanthrene carboxylic acids primarily found in plants of the Aristolochiaceae family. Aristolochic acid D (AAD) is a major constituent in the roots and rhizomes of the Chinese herb Xixin (the roots and rhizomes of Asarum heterotropoides F. Schmidt), which is a key material for preparing a suite of marketed Chinese medicines. Structurally, AAD is nearly identical to the nephrotoxic aristolochic acid I (AAI), with an additional phenolic group at the C-6 site. Although the nephrotoxicity and metabolic pathways of AAI have been well-investigated, the metabolic pathway(s) of AAD in humans and the influence of AAD metabolism on its nephrotoxicity has not been investigated yet. To identify the major metabolites of AAD in human tissues and to characterize AAD O -glucuronidation kinetics in different enzyme sources, as well as to explore the influence of AAD O -glucuronidation on its nephrotoxicity. The O -glucuronide of AAD was biosynthesized and its chemical structure was fully characterized by both 1H-NMR and 13C-NMR. Reaction phenotyping assays, chemical inhibition assays, and enzyme kinetics analyses were conducted to assess the crucial enzymes involved in AAD O -glucuronidation in humans. Docking simulations were performed to mimic the catalytic conformations of AAD in human UDP-glucuronosyltransferases (UGTs), while the predicted binding energies and distances between the deprotonated C-6 phenolic group of AAD and the glucuronyl moiety of UDPGA in each tested human UGT isoenzyme were measured. The mitochondrial membrane potentials (MMP) and reactive oxygen species (ROS) levels in HK-2 cells treated with either AAI, or AAD, or AAD O -glucuronide were tested, to elucidate the impact of O -glucuronidation on the nephrotoxicity of AAD. AAD could be rapidly metabolized in human liver and intestinal microsomes (HLM and HIM, respectively) to form a mono-glucuronide, which was purified and fully characterized as AAD-6- O -β-D-glucuronide (AADG) by NMR. UGT1A1 was the predominant enzyme responsible for AAD-6- O -glucuronidation, while UGT1A9 contributed to a lesser extent. AAD-6- O -glucuronidation in HLM, HIM, UGT1A1 and UGT1A9 followed Michaelis-Menten kinetics, with the K m values of 4.27 μM, 9.05 μM, 3.87 μM, and 7.00 μM, respectively. Docking simulations suggested that AAD was accessible to the catalytic cavity of UGT1A1 or UGT1A9 and formed catalytic conformations. Further investigations showed that both AAI and AAD could trigger the elevated intracellular ROS levels and induce mitochondrial dysfunction and in HK-2 cells, but AADG was hardly to trigger ROS accumulation and mitochondrial dysfunction. Collectively, UGT1A-catalyzed AAD 6- O -glucuronidation represents a crucial detoxification pathway of this naturally occurring AAI analogs in humans, which is very different from that of AAI. Aristolochic acid D (AAD), an abundant naturally occurring aristolochic acid derivative isolated from the Chinese herb Xixin (the roots and rhizomes of Asarum heterotropoides F. Schmidt), can be rapidly converted into AAD-6- O -β-D-glucuronide (AADG) in human tissue preparations. UGT1A-catalyzed AAD 6- O -glucuronidation offers a crucial detoxification pathway of this aristolochic acid derivative in humans, which is very different from that of the nephrotoxin aristolochic acid I (AAI). [Display omitted] • AAD- O -glucuronidation was a major metabolic pathway of AAD in humans. • The glucuronide was biosynthesized and characterized as AAD-6- O -β-D-glucuronide. • UGT1A1 was the predominant enzyme responsible for AAD-6- O -glucuronidation. • AAD-6- O -glucuronidation offers a crucial detoxification pathway of AAD in humans. [ABSTRACT FROM AUTHOR]

Methylophiopogonanone A (MOA) is an abundant homoisoflavonoid in the Chinese herb Ophiopogonis Radix. Recent investigations revealed that MOA inhibited several human cytochrome P450 enzymes (CYPs) and stimulated OATP1B1. However, the inhibitory effects of MOA on phase II drug‐metabolizing enzymes, such as human UDP‐glucuronosyltransferases (hUGTs), have not been well investigated. Herein, the inhibition potentials of MOA on hUGTs were assessed. The results clearly demonstrated that MOA dose‐dependently inhibited all tested hUGTs including UGT1A1 (IC50 = 1.23 μM), one of the most important detoxification enzymes in humans. Further investigations showed that MOA strongly inhibited UGT1A1‐catalysed NHPH‐O‐glucuronidation in a range of biological settings including hUGT1A1, human liver microsomes (HLM) and HeLa cells overexpressing UGT1A1. Inhibition kinetic analyses demonstrated that MOA competitively inhibited UGT1A1‐catalysed NHPH‐O‐glucuronidation in both hUGT1A1 and HLM, with Ki values of 0.52 and 1.22 μM, respectively. Collectively, our findings expanded knowledge of the interactions between MOA and human drug‐metabolizing enzymes, which would be very helpful for guiding the use of MOA‐related herbal products in clinical settings. [ABSTRACT FROM AUTHOR]

Strong inhibition of the human UDP-glucuronosyltransferase enzymes (UGTs) may lead to undesirable effects, including hyperbilirubinaemia and drug/herb-drug interactions. Currently, there is no good way to examine the inhibitory effects and specificities of compounds toward all the important human UGTs, side-by-side and under identical conditions. Herein, we report a new, broad-spectrum substrate for human UGTs and its uses in screening and characterizing of UGT inhibitors. Following screening a variety of phenolic compound(s), we have found that methylophiopogonanone A (MOA) can be readily O -glucuronidated by all tested human UGTs, including the typical N -glucuronidating enzymes UGT1A4 and UGT2B10. MOA- O -glucuronidation yielded a single mono- O -glucuronide that was biosynthesized and purified for structural characterization and for constructing an LC-UV based MOA- O -glucuronidation activity assay, which was then used for investigating MOA- O -glucuronidation kinetics in recombinant human UGTs. The derived K m values were crucial for selecting the most suitable assay conditions for assessing inhibitory potentials and specificity of test compound(s). Furthermore, the inhibitory effects and specificities of four known UGT inhibitors were reinvestigated by using MOA as the substrate for all tested UGTs. Collectively, MOA is a broad-spectrum substrate for the human UGTs, which offers a new and practical tool for assessing inhibitory effects and specificities of UGT inhibitors. • MOA is a broad substrate for human UGTs with O -glucuronidation activity. • MOA- O -glucuronidation kinetics in 13 human UGTs were investigated. • An LC-UV based MOA- O -glucuronidation activity assay was developed and used for screening and characterizing UGT inhibitors. • The specificities of four known UGT inhibitors were reinvestigated by using MOA as the substrate. [ABSTRACT FROM AUTHOR]

Corona Virus Disease 2019 (COVID-19) has spread all over the world and brings significantly negative effects on human health. To fight against COVID-19 in a more efficient way, drug-drug or drug-herb combinations are frequently used in clinical settings. The concomitant use of multiple medications may trigger clinically relevant drug/herb-drug interactions. This study aims to assay the inhibitory potentials of Qingfei Paidu decoction (QPD, a Chinese medicine compound formula recommended for combating COVID-19 in China) against human drug-metabolizing enzymes and to assess the pharmacokinetic interactions in vivo. The results demonstrated that QPD dose-dependently inhibited CYPs1A, 2A6, 2C8, 2C9, 2C19, 2D6 and 2E1 but inhibited CYP3A in a time- and NADPH-dependent manner. In vivo test showed that QPD prolonged the half-life of lopinavir (a CYP3A substrate-drug) by 1.40-fold and increased the AUC of lopinavir by 2.04-fold, when QPD (6 g/kg) was co-administrated with lopinavir (160 mg/kg) to rats. Further investigation revealed that Fructus Aurantii Immaturus (Zhishi) in QPD caused significant loss of CYP3A activity in NADPH-generating system. Collectively, our findings revealed that QPD potently inactivated CYP3A and significantly modulated the pharmacokinetics of CYP3A substrate-drugs, which would be very helpful for the patients and clinicians to avoid potential drug-interaction risks in COVID-19 treatment. Image 1 • Qingfei Paidu decoction (QPD) dose-dependently inhibits CYPs1A, 2A6, 2C8, 2C9, 2C19, 2D6 and 2E1 in a reversible manner. • QPD inhibits CYP3A in a time- and NADPH-dependent manner in liver microsomes from both humans and rats. • QPD significantly increases the plasma exposure and half-life of lopinavir in rats. • Fructus Aurantii Immaturus (Zhishi) in QPD plays a crucial role in CYP3A inactivation. [ABSTRACT FROM AUTHOR]

• Series of chalcone-like compounds are designed and synthesized as inhibitors of pancreatic lipase (PL). • Structure-activity relationships of chalcone-like compounds as PL inhibitors are summarized. • B13 potently inhibits PL in a reversible and mixed inhibition manner. • B13 displays potent PL inhibition activity and good stability in gastrointestinal fluids and human liver preparations. Pancreatic lipase (PL), a crucial enzyme responsible for hydrolysis of dietary lipids, has been validated as a key therapeutic target to prevent and treat obesity-associated metabolic disorders. Herein, we report the design, synthesis and biological evaluation of a series of chalcone-like compounds as potent and reversible PL inhibitors. Following two rounds of structural modifications at both A and B rings of a chalcone-like skeleton, structure-PL inhibition relationships of the chalcone-like compounds were studied, while the key substituents that would be beneficial for PL inhibition were revealed. Among all tested chalcone-like compounds, compound B13 (a novel chalcone-like compound bearing two long carbon chains) displayed the most potent PL inhibition activity, with an IC 50 value of 0.33 μM. Inhibition kinetic analyses demonstrated that B13 could potently inhibit PL-mediated 4-MUO hydrolysis in a mixed inhibition manner, with the K i value of 0.12 μM. Molecular docking simulations suggested that B13 could tightly bind on PL at both the catalytic site and a non-catalytic site that was located on the surface of PL, which was consistent with the mixed inhibition mode of this agent. In addition, B13 displayed excellent stability in artificial gastrointestinal fluids and good metabolic stability in human liver preparations. Collectively, our findings suggested that chalcone-like compounds were good choices for design and development of orally administrated PL inhibitors, while B13 could be served as a promising lead compound to develop novel anti-obesity agents via targeting on PL. [ABSTRACT FROM AUTHOR]