The Chinese herb Styrax triggers pharmacokinetic herb-drug interactions via inhibiting intestinal CYP3A.

Human cytochrome P450 3A4 (hCYP3A4) is a predominant enzyme to trigger clinically relevant drug/herb-drug interactions (DDIs or HDIs). Although a number of herbal medicines have been found with strong anti-hCYP3A4 effects in vitro, the in vivo modulatory effects of herbal medicines on hCYP3A4 and their potential risks to trigger HDIs are rarely investigated. Herein, we demonstrate a case study to efficiently find the herbal medicine(s) with potent hCYP3A4 inhibition in vitro and to accurately assess the potential HDIs risk in vivo. Following screening over 100 herbal medicines, the Chinese herb Styrax was found with the most potent hCYP3A4 inhibition in HLMs. In vitro assays demonstrated that Styrax could potently inhibit mammalian CYP3A in liver and intestinal microsomes from both humans and rats. In vivo pharmacokinetic assays showed that Styrax (i.g., 100 mg/kg) significantly elevated the plasma exposure of two CYP3A-substrate drugs (midazolam and felodipine) when midazolam or felodipine was administered orally. By contrast, the plasma exposure of either midazolam or felodipine was hardly affected by Styrax (i.g.) when the victim drug was administered intravenously. Further investigations demonstrated that seven pentacyclic triterpenoid acids (PTAs) in Styrax were key substances responsible for CYP3A inhibition, while these PTAs could be exposed to intestinal tract at relatively high exposure levels but their exposure levels in rat plasma and liver were extremely low. These findings well explained why Styrax (i.g.) could elevate the plasma exposure of victim drugs only when these agents were orally administrated. Collectively, our findings demonstrate that Styrax can modulate the pharmacokinetic behavior of CYP3A-substrate drugs via inhibiting intestinal CYP3A, which is very helpful for the clinical pharmacologists to better assess the HDIs triggered by Styrax or Styrax-related herbal products.

Inhibition of drug-metabolizing enzymes by Jingyin granules: implications of herb-drug interactions in antiviral therapy.

Jingyin granules, a marketed antiviral herbal medicine, have been recommended for treating H1N1 influenza A virus infection and Coronavirus disease 2019 (COVID-19) in China. To fight viral diseases in a more efficient way, Jingyin granules are frequently co-administered in clinical settings with a variety of therapeutic agents, including antiviral drugs, anti-inflammatory drugs, and other Western medicines. However, it is unclear whether Jingyin granules modulate the pharmacokinetics of Western drugs or trigger clinically significant herb-drug interactions. This study aims to assess the inhibitory potency of the herbal extract of Jingyin granules (HEJG) against human drug-metabolizing enzymes and to clarify whether HEJG can modulate the pharmacokinetic profiles of Western drug(s) in vivo. The results clearly demonstrated that HEJG dose-dependently inhibited human CES1A, CES2A, CYPs1A, 2A6, 2C8, 2C9, 2D6, and 2E1; this herbal medicine also time- and NADPH-dependently inhibited human CYP2C19 and CYP3A. In vivo tests showed that HEJG significantly increased the plasma exposure of lopinavir (a CYP3A-substrate drug) by 2.43-fold and strongly prolonged its half-life by 1.91-fold when HEJG (3 g/kg) was co-administered with lopinavir to rats. Further investigation revealed licochalcone A, licochalcone B, licochalcone C and echinatin in Radix Glycyrrhizae, as well as quercetin and kaempferol in Folium Llicis Purpureae, to be time-dependent CYP3A inhibitors. Collectively, our findings reveal that HEJG modulates the pharmacokinetics of CYP substrate-drug(s) by inactivating CYP3A, providing key information for both clinicians and patients to use herb-drug combinations for antiviral therapy in a scientific and reasonable way.

Methylophiopogonanone A is a naturally occurring broad-spectrum inhibitor against human UDP-glucuronosyltransferases: Inhibition behaviours and implication in herb-drug interactions.

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.

Inhibition of drug-metabolizing enzymes by Qingfei Paidu decoction: Implication of herb-drug interactions in COVID-19 pharmacotherapy.

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.

Inhibition of UDP-glucuronosyltransferases by different furoquinoline alkaloids.

Herbs are often administered in combination with therapeutic drugs, raising the possibility for herb-drug interactions (HDIs). Furoquinoline alkaloids are found in Rutaceae plants, which are structurally similar and have many medicinal properties. This study aims to investigate the inhibition of four furoquinoline alkaloids on the activity of UDP-glucuronosyltransferases (UGTs).The recombinant UGTs-catalyzed glucuronidation metabolism of 4-methylumbelliferone (4-MU) was utilized to investigate the inhibition potential. Inhibition type and parameters were determined, and in silico docking was employed to elucidate the inhibition difference of furoquinoline alkaloids towards UGTs.Dictamine, haplopine, γ-fagarine and skimmianine strongly inhibited UGT1A3, UGT1A7, UGT1A9 and UGT2B4, respectively. Among them, dictamnine inhibited more than 70% of the four UGTs. Inhibition kinetics determination showed that they all exerted competitive inhibition, and the inhibition kinetic constant (Ki) was determined to be 8.3, 7.2, 3.7 and 33.9 µM, respectively. In vitro-in vivo extrapolation (IVIVE) was employed to demonstrate the inhibition possibility for four alkaloids. Skimmianine was proved to be more suitable for clinical application. In silico docking study indicated that the hydrophobic interactions played a key role in the inhibition of furoquinoline alkaloids towards three of the four UGTs. In conclusion, monitoring the interactions between furoquinoline alkaloids and drugs mainly undergoing UGTs-catalyzed metabolism is necessary.

Inhibition of human carboxylesterases by magnolol: Kinetic analyses and mechanism.

Magnolol, the most abundant bioactive constituent of the Chinese herb Magnolia officinalis, has been found with multiple biological activities, including anti-oxidative, anti-inflammatory and enzyme-regulatory activities. In this study, the inhibitory effects and inhibition mechanism of magnolol on human carboxylesterases (hCEs), the key enzymes responsible for the hydrolytic metabolism of a variety of endogenous esters as well as ester-bearing drugs, have been well-investigated. The results demonstrate that magnolol strongly inhibits hCE1-mediated hydrolysis of various substrates, whereas the inhibition of hCE2 by magnolol is substrate-dependent, ranging from strong to moderate. Inhibition of intracellular hCE1 and hCE2 by magnolol was also investigated in living HepG2 cells, and the results showed that magnolol could strongly inhibit intracellular hCE1, while the inhibition of intracellular hCE2 was weak. Inhibition kinetic analyses and docking simulations revealed that magnolol inhibited both hCE1 and hCE2 in a mixed manner, which could be partially attributed to its binding at two distinct ligand-binding sites in each carboxylesterase, including the catalytic cavity and the regulatory domain. In addition, the potential risk of the metabolic interactions of magnolol via hCE1 inhibition was predicted on the basis of a series of available pharmacokinetic data and the inhibition constants. All these findings are very helpful in deciphering the metabolic interactions between magnolol and hCEs, and also very useful for avoiding deleterious interactions via inhibition of hCEs.

Drug interaction study of flavonoids toward CYP3A4 and their quantitative structure activity relationship (QSAR) analysis for predicting potential effects.

The high risk of herb-drug interactions (HDIs) mediated by the herbal medicines and dietary supplements which containing abundant flavonoids had become more and more frequent in our daily life. In our study, the inhibition activities of 44 different structures of flavonoids toward human CYPs were systemically evaluated for the first time. According to our results, a remarkable structure-dependent inhibition behavior toward CYP3A4 was observed in vitro. Some flavonoids such as licoflavone (12) and irilone (30) exhibited the selective inhibition toward CYP3 A4 rather than other major human CYPs. To illustrate the interaction mechanism, the inhibition kinetics of various compounds was further performed. Sophoranone (1), apigenin (10), baicalein (11), 5,4'-dihydroxy-3,6,7,8,3'-pentamethoxyflavone (15), myricetin (23) and kushenol K (38) remarkably inhibited the CYP3 A4-catalyzed bufalin 5'-hydroxylation reaction, with Ki values of 2.17 ±â€¯0.29, 6.15 ±â€¯0.39, 9.18 ±â€¯3.40, 2.30 ±â€¯0.36, 5.00 ±â€¯2.77 and 1.35 ±â€¯0.25 µM, respectively. Importantly, compounds 1, 11, 15, 23 and 38 could significantly inhibit the metabolism of some clinical drugs in vitro, and these drug-drug interactions (DDIs) of myricetin (23) or kushenol K (38) with clinical drug diazepam were further verified in human primary hepatocytes, respectively. Finally, a quantitative structure-activity relationship (QSAR) of flavonoids with their inhibitory effects toward CYP3 A4 was established using computational methods. Our findings illustrated the high risk of herb-drug interactions (HDIs) caused by flavonoids and revealed the vital structures requirement of natural flavonoids for the HDIs with clinical drugs eliminated by CYP3 A4. Our research provided the useful guidance to safely and rationally use herbal medicines and dietary supplements containing rich natural flavonoids components.

Amentoflavone is a potent broad-spectrum inhibitor of human UDP-glucuronosyltransferases.

Amentoflavone (AMF), an abundant natural biflavonoid found in many medicinal plants, displays various beneficial effects including anti-inflammatory, anti-oxidative and anti-cancer. Despite the extensive studies on pharmacological activities, the toxicity or undesirable effects of AMF are rarely reported. In this study, the inhibitory effects of AMF on human UDP-glucuronosyltransferases (UGTs) were carefully investigated. AMF displayed strong inhibition towards most of human UGTs including UGT1A1, 1A3, 1A4, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4 and 2B17, with the IC50 values ranging from 0.12 µM to 16.81 µM. Inhibition constants (Ki) of AMF against various human UGTs varied from 0.29 µM to 11.51 µM. Further investigation demonstrated that AMF was a noncompetitive inhibitor of UGT1A1 mediated NCHN-O-glucuronidation but functioned as a competitive inhibitor of UGT1A1 mediated 4-MU-O-glucuronidation. In addition, AMF was a competitive inhibitor of UGT1A4 mediated TFP-N-glucuronidation in both UGT1A4 and human liver microsomes, while functioned as a competitive inhibitor of UGT1A9 mediated propofol or 4-MU-O-glucuronidation. These findings demonstrated that AMF was a strong and broad-spectrum natural inhibitor of most human UGTs, which might bring potential risks of herb-drug interactions (HDIs) via UGT inhibition. Additionally, this study provided novel insights into the underlying mechanism of AMF-associated toxicity from the perspective of UGT inhibition.

Assessment of the inhibition potential of Licochalcone A against human UDP-glucuronosyltransferases.

Licochalcone A (LCA) is a major bioactive compound in Licorice, a widely used herbal medicine. In this study, the inhibitory effects of LCA against human UDP-glucuronosyltransferases (UGTs) and LCA associated herb-drug interactions were systematically investigated. Our results demonstrated that LCA displayed broad-spectrum inhibition against human UGTs. LCA exhibited strong inhibitory effects against UGT1A1, 1A3, 1A4, 1A6, 1A7, 1A9, and 2B7 (both IC50 and Ki values lower than 5 µM), while showing moderate inhibitory effects against UGT1A8, 1A10, 2B4, 2B15, and 2B17. The inhibitory effects of LCA against two major UGTs, including UGT1A1 and 1A9, were further investigated in human liver microsomes (HLMs), where the potential risks of LCA via inhibition of UGT1A1 and 1A9 were predicted by combining the in vitro inhibitory data and physiological data. The results from this study also showed that several LCA-containing products were able to increase the area under the curve (AUC) of the substrates that were predominantly metabolized by UGT1A1 or 1A9. These findings together demonstrate that LCA has a potent and broad-spectrum inhibitory effect against most human UGTs and thus suggest that much caution should be exercised when high-dose LCA is co-administered with UGT substrates.

Inhibition of human cytochrome P450 enzymes by licochalcone A, a naturally occurring constituent of licorice.

Licochalcone A (LCA) is a major bioactive compound in traditional Chinese herbal liquorice that possesses multiple pharmacological activities. However, the effects of the potential herb-drug interactions (HDIs) between LCA and therapeutic drugs on the inhibition of human cytochrome P450 (CYP) enzymes remain unclear. In the present study, the inhibitory effects of LCA on seven major human CYP isoforms, including CYP1A2, 2D6, 2E1, 2C19, 2C8, 2C9 and 3A4, were investigated in human liver microsomes (HLMs). The results demonstrated that LCA significantly inhibited the activities of CYP1A2, 2C19, 2C8, 2C9 and 3A4 and exhibited weak inhibitory effects on CYP2E1 and CYP2D6. Dixon and Lineweaver-Burk plots revealed that the inhibition types of LCA against CYP1A2, 2C9, 2C19 and 2C8 were best fit as mixed-type inhibitions, while LCA was a competitive inhibitor towards CYP3A4. The inhibition kinetic parameters (K(i)) were calculated to be 1.02 µM, 0.17 µM, 3.89 µM 0.89 µM, and 2.29 µM, for CYP1A2, 2C9, 2C19, 2C8, and 3A4, respectively. Furthermore, the areas under the plasma concentration-time curves (AUCs) of several drugs that are primarily metabolized by CYPs were estimated to increase by 2-398% in the presence of LCA, which suggested that LCA exhibited high HDI potentials via CYP inhibition. These data are significant for the clinical applications of LCA-containing herbs.