Human microsomal cyttrochrome P450-mediated reduction of oxysophocarpine, an active and highly toxic constituent derived from Sophora flavescens species, and its intestinal absorption and metabolism in rat

Quinolizidine-Type Alkaloids: Chemodiversity, Occurrence, and Bioactivity

Quinolizidine alkaloids (QAs) are nitrogen-containing compounds produced naturally as specialized metabolites distributed in plants and animals (e.g., frogs, sponges). The present review compiles the available information on the chemical diversity and biological activity of QAs reported during the last three decades. So far, 397 QAs have been isolated, gathering 20 different representative classes, including the most common such as matrine (13.6%), lupanine (9.8%), anagyrine (4.0%), sparteine (5.3%), cytisine (6.5%), tetrahydrocytisine (4.3%), lupinine (12.1%), macrocyclic bisquinolizidine (9.3%), biphenylquinolizidine lactone (7.1%), dimeric (7.1%), and other less known QAs (20.9%), which include several structural patterns of QAs. A detailed survey of the reported information about the bioactivities of these compounds indicated their potential as cytotoxic, antiviral, antimicrobial, insecticidal, anti-inflammatory, antimalarial, and antiacetylcholinesterase compounds, involving favorable putative drug-likeness scores. In this regard, research progress on the structural and biological/pharmacological diversity of QAs requires further studies oriented on expanding the chemical space to find bioactive scaffolds based on QAs for pharmacological and agrochemical applications.

Insights into oral bioavailability enhancement of therapeutic herbal constituents by cytochrome P450 3A inhibition

Herbal plants typically have complex compositions and diverse mechanisms. Among them, bioactive constituents with relatively high exposure in vivo are likely to exhibit therapeutic efficacy. On the other hand, their bioavailability may be influenced by the synergistic effects of different bioactive components. Cytochrome P450 3A (CYP3A) is one of the most abundant CYP enzymes, responsible for the metabolism of 50% of approved drugs. In recent years, many therapeutic herbal constituents have been identified as CYP3A substrates. It is more evident that CYP3A inhibition derived from the herbal formula plays a critical role in improving the oral bioavailability of therapeutic constituents. CYP3A inhibition may be the mechanism of the synergism of herbal formula. In this review, we explored the multiplicity of CYP3A, summarized herbal monomers with CYP3A inhibitory effects, and evaluated herb-mediated CYP3A inhibition, thereby providing new insights into the mechanisms of CYP3A inhibition-mediated oral herb bioavailability.

An In Vitro Study for Evaluating Permeability and Metabolism of Kurarinone

Kurarinone is a major component found in the dried roots of Sophora flavescens Ait. that participates in vital pharmacological activities. Recombinant CYP450 supersomes and liver microsomes were used to study the metabolic profiles of kurarinone and its inhibitory actions against cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT) enzymes. 100 μM of kurarinone strongly inhibited more than 90% of UGT1A1, UGT1A6, CYP1A2, and CYP2C9. CYP1A2 and CYP2D6 played important roles in catalyzing the biotransformation of kurarinone. Moreover, metabolism of kurarinone considerably differs among species, and metabolic characteristics were similar between monkey and human. Kurarinone demonstrated moderate permeability at values of pH 4.0 and 7.4. Our findings offer a clearer idea to understand the pharmacological and toxicological mechanisms of kurarinone.

Oxysophocarpine suppresses hepatocellular carcinoma growth and sensitizes the therapeutic blockade of anti-Lag-3 via reducing FGL1 expression

Hepatocellular carcinoma (HCC) is an aggressive malignancy with limited effective treatments and ranks as the second most lethal tumor. Immunotherapy has brought great hope for HCC treatment. Oxysophocarpine is a bioactive alkaloid which poses various pharmacological functions including neuroprotective, anti‐virus, anti‐convulsant, and anti‐nociception. However, there is little systematic study of Oxysophocarpine against HCC and its underlying potential and mechanism combined with immunotherapy in HCC treatment remain poorly unknown. This study was aimed to investigate whether Oxysophocarpine can distinctly suppress HCC cells and sensitize the immunotherapy of CD8⁺ T cells against HCC. We used HepG2, Hepa1‐6, and primary CD8⁺ T cells to perform in vitro assays and Hepa1‐6 subcutaneous tumor to conduct in vivo assay. Oxysophocarpine inhibited the proliferation and increased the apoptosis of HepG2 and Hepa1‐6 cells, meanwhile suppressed the migration of HepG2 and Hepa1‐6 cells. Oxysophocarpine sensitized the Lag‐3 immunotherapy effect of CD8⁺ T cells against HCC in vivo and in vitro by decreasing Fibrinogen‐like protein 1 (FGL1) expression through downregulating IL‐6‐mediated JAK2/STAT3 signaling, whereas Oxysophocarpine treatment had a little effect of CD8⁺ T cells cytotoxicity function against HCC with PD‐1, Tim‐3, or TIGIT blockade. Our studies provided preclinical basis for clinical application of Oxysophocarpine.

Gender Differences in the Hepatotoxicity and Toxicokinetics of Emodin: The Potential Mechanisms Mediated by UGT2B7 and MRP2

Emodin is a main anthraquinone compound which exists in Chinese traditional medicines including Polygonum multiflorum and Rhubarb. It is documented to have obvious liver and kidney toxicity. This study aims to (a) estimate gender differences of the hepatotoxicity and toxicokinetics in rats after oral administration of emodin (60 and 150 mg/kg/d) for a consecutive 28 days and (b) clarify relative mechanisms caused by glucuronidation and disposition. Hepatotoxicity was significantly higher in female rats than that in male rats, as evidenced by histopathological and biochemical tests. Similarly, the toxicokinetic profiles of emodin have time and gender differences, which could cause time and gender differences in hepatotoxicity. The metabolic and transcriptomics data of 55 human liver and 36 human kidney samples demonstrated that UDP-glucuronosyltransferase 2B7 (UGT2B7) was the predominant enzyme for emodin glucuronidation. A genome-wide association study (GWAS) identified that rs11726899 located within ∼50 kb of the transcript of UGT2B could significantly affect emodin metabolism. Knockdown of UGT2B7 in HepG2 cells significantly decreased emodin glucuronidation and increased cytotoxicity of emodin. The gene expression and protein levels of UGT2B7 were decreased, but those of the multidrug-resistant-protein 2 (MRP2) were increased in HepG2 cells after being treated with 50 μM emodin for 48 h. Long-term use of emodin could decrease the intrinsic clearance (CL_int, decreased by 18.5%-35.4%) values of zidovidue (UGT2B7 substrate) glucuronide in both male and female liver microsomes from rats administrated with emodin for 28 days, thus causing the accumulation of emodin. However, higher self-induced MRP2 expression and lower hepatotoxicity were observed in emodin-treated male rats compared to that in female rats. Therefore, gender differences in the hepatotoxicity and toxicokinetics of emodin are potentially mediated by the coupling of UGT2B7 and MRP2 in vivo.

The profiling and identification of chemical components, prototypes and metabolites of Run-zao-zhi-yang capsule in rat plasma, urine and bile by an UPLC-Q-TOF/MSE -based high-throughput strategy

Run-zao-zhi-yang (RZZY) capsule, a traditional Chinese medicine formula, is popularly used for the treatment of dermatitis and eczema. However, few studies have been carried out on RZZY and its metabolites. In this study, we developed a three-step strategy to rapidly characterize the chemical constituents and metabolites of RZZY using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. A total of 41 chemical components were characterized from RZZY. Among these, there are 11 flavonoids, six alkaloids, six stilbene glycosides, five anthraquinones and 13 other compounds. In addition, 18 prototypes and 35 metabolites were detected in rat plasma, urine and bile. This study offers an applicable approach for high-throughput profiling and identification of chemical components and metabolites derived from traditional Chinese medicine formula in vivo, and also provides essential data for exploring bioactive ingredients and action mechanisms of RZZY.

UGT-mediated metabolism plays a dominant role in the pharmacokinetic behavior and the disposition of morusin in vivo and in vitro

Morusin is a prenylated flavone isolated from mulberry, the branch and root bark of various Morus species, which possesses diverse pharmacological activities. However, it lacks extensive studies about its absorption and disposition. This study investigated the pharmacokinetic behavior of morusin in rat, and its first-pass metabolism in situ. The metabolic pathway of morusin was further investigated by 12 human recombinant UDP-glucuronosyltransferases (UGTs), 9 CYP450s, as well as liver and intestinal microsomes. Four mono-glucuronide metabolites (M-5-G, M-4'-G, M-2'-G, and M_II-2) were identified in rat intestine and bile by LC-MS/MS, while three of them were also detected in plasma (M-5-G, M-4'-G, and M_II-2). M-4'-G was the principal conjugate. However, few CYP450 metabolites were found in rat intestine and bile. Only a small amount of M_I-1 could be detected in rat plasma. UGT1A1, 1A3, 1A7, and 2B7 were the major contributors to morusin glucuronidation. Morusin exhibited substrate inhibition kinetic characteristics in all UGTs. Clearance rates of M-4'-G in HLM, RLM, UGT1A1, UGT1A3, and UGT2B7 were 137.02, 127.55, 32.54, 41.18, and 35.07 ml/min/mg, respectively. Besides, CYP3A5, 3A4, and 2C19 primarily contributed to the oxidative metabolism of morusin. The pharmacokinetic curves of morusin and its conjugates presented double peaks, showing that an enterohepatic recycling may exist. In conclusion, glucuronidation was confirmed to be the crucial metabolic pathway for morusin in vivo, and M-4'-G was the main metabolite.

Antibacterial and synergistic effects of the n-BuOH fraction of Sophora flavescens root against oral bacteria

The antibacterial activity of an extract and several fractions of Sophora flavescens (S. flavescens) root alone and in combination with antibiotics against oral bacteria was investigated by checkerboard assay and time-kill assay. The minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC) values for all examined bacteria were 0.313-2.5/0.625-2.5 μg/mL for the n-BuOH fraction, 0.625-5/1.25-10 μg/mL for the EtOAc fraction, 0.25-8/0.25-16 μg/mL for ampicillin, 0.5-256/1-512 μg/mL for gentamicin, 0.008-32/0.016-64 μg/mL for erythromycin, and 0.25-64/0.5-128 μg/mL for vancomycin. The n-butanol (n-BuOH) and ethyl acetate (EtOAc) fractions exhibited stronger antibacterial activity against oral bacteria than other fractions and extracts. The MICs and MBCs were reduced to between one half and one quarter when the n-BuOH and EtOAc fractions were combined with antibiotics. After 24 h of incubation, combination of 1/2 MIC of the n-BuOH fraction with antibiotics increased the degree of bactericidal activity. The present results suggest that n-BuOH and EtOAc extracts of S. flavescens root might be applicable as new natural antimicrobial agents against oral pathogens.

Effects of Paederia foetida and its Bioactive Phytochemical Constituent Lupeol on Hepatic Phase I Drug Metabolism

There are many possible complications associated with the concomitant use of herbs and medications, but limited information is available on herb-herb or herb-drug interactions. Paederia foetida Linn. (family: Rubiaceae) is utilized in the Indian traditional medicine. It exhibits various pharmacological properties, such as antidiabetic, analgesic, anti-inflammatory, antimicrobial, hepatoprotective, anthelmintic, antiulcer and antioxidant activities. The purpose of the present work was to investigate the inhibitory potential of the P. foetida ethanolic extract and its bioactive constituent lupeol on hepatic phase I drug metabolizing enzymes. The high performance thin layer chromatography was performed for qualitative analysis of various extracts of P. foetida. The effects of P. foetida extract on rat liver microsomes (RLMs) and individual cytochrome P-450 (CYP) isozymes (CYP3A4 and CYP2D6) were investigated using CYP450-carbon monoxide complex assay and fluorescence microplate assay, respectively. The ethanolic extract and lupeol (both at a concentration of 100 μg/mL) showed 45±3.3 and 44±3.8% inhibition of rat liver microsomes, respectively, which were significantly less than that of known inhibitor ketoconazole (74±5.4% inhibition at 100 μg/mL). The 50% inhibitory concentrations (IC50) of ethanolic extract on CYP3A4 and CYP2D6 were 78±2.3 and 82±3.1 μg/mL, respectively, whereas its major bioactive constituent lupeol has IC50 values of 83±2.0 and 84±2.6 μg/mL for CYP3A4 and CYP2D6, respectively. The results were of lesser magnitude compared to known inhibitors, ketoconazole and quinidine, respectively. The current study revealed that P. foetida has less inhibitory potential in comparison to that of known inhibitors, ketoconazole and quinidine, on two major drug metabolizing isozymes, CYP3A4 and CYP2D6. Thus, the use of P. foetida as a complementary or alternative medicine may be safe in regard to herb-drug interactions.

Flavokawain A inhibits Cytochrome P450 in in vitro metabolic and inhibitory investigations

ETHNOPHARMACOLOGICAL RELEVANCE

Flavokawain A, the major chalcone in kava extracts, was served as beverages for informal social occasions and traditional ceremonials in most South Pacific islands. It exhibited strong antiproliferative and apoptotic effects against human prostate and urinary bladder cancer cells.

AIM OF THE STUDY

The current study was purposed to investigate the interaction between Flavokawain A and Cytochrome P450, including the inhibitory effects of Flavokawain A on predominant CYP450 isotypes and further clarified the inhibitory mechanism of FKA on CYP450 enzymes. Besides, study about identifying the key CYP450 isotypes responsible for the metabolism of FKA was also performed.

MATERIALS AND METHODS

In this study, probe-based assays with rat liver microsome system were used to characterize the inhibitory effects of FKA. Molecular docking study was performed to further explore the binding site of FKA on CYP450 isoforms. In addition, chemical inhibition experiments using specific inhibitors (a-naphthoflavone, quinidine, sulfamethoxazde, ketoconazole, omeprazole) were performed to clarify the individual CYP450 isoform that are responsible for the metabolism of FKA.

RESULTS

FKA showed significant inhibition on CYP1A2, CYP2D1, CYP2C6 and CYP3A2 activities with IC50 values of 102.23, 20.39, 69.95, 60.22μmol/L, respectively. The inhibition model was competitive, mixed-inhibition, uncompetitive, and noncompetitive for CYP1A2, CYP2D1, CYP2C6 and CYP3A2 enzymes. Molecular docking study indicated the ligand-binding conformation of FKA in the active site of CYP450 isoforms. The chemical inhibition experiments showed that the metabolic clearance rate of Flavokawain A decreased to 19.84%, 50.38%, and 67.02% of the control in the presence of ketoconazole, sulfamethoxazde and a-naphthoflavone.

CONCLUSION

The study showed that Flavokawain A has varying inhibitory effect on CYP450 enzymes and CYP3A2 was the principal CYP isoform contributing to the metabolism of Flavokawain A. Besides, CYP2C6 and CYP1A2 isoforms also play important roles in the metabolism of FKA. Our results provided a basis for better understanding the biotransformation of FKA and prediction of drug-drug interaction of FKA.