The characterisation of the in vitro metabolism and transport of 6-hydroxykynurenic acid, an important constituent of Ginkgo biloba extracts.

6-Hydroxykynurenic acid (6-HKA) is a nitrogen-containing phenolic acid compound in Ginkgo biloba leaves. The pharmacological activities of 6-HKA have been reported and shown that 6-HKA has the potential to become a therapeutic drug and may play an important role in the treatment of nervous system diseases. However, there are few studies on the drug metabolism and transport of 6-HKA. The aim of this study is to investigate the in vitro metabolism of 6-HKA and its interaction with multiple important drug transporters.The in vitro metabolism experiments in the present study demonstrate that 6-HKA might not undergo phase-I or phase-II metabolism in hepatic microsomes/S9 of rats. In addition, some drug transporters, including OAT1/3, OCT2, MDR1, OATP1B1, MATE1/2K and OCTN2, were investigated. The cellular uptake assays indicate that 6-HKA exhibits inhibition to the transport of classical substrates mediated by OAT3, OCT2, MATE2K and OCTN2 but has no significant effect on the transport of substrates mediated by MDR1, OAT1, OATP1B1 or MATE1. Further investigation of cellular accumulation assays shows that 6-HKA might be the substrate of OAT3, but not OCT2 or OCTN2. The bidirectional transport study suggests that 6-HKA is not a substrate of MDR1.The information about the in vitro metabolism of 6-HKA and the interaction between 6-HKA and some transporters will help us to better understand the pharmacokinetic properties of 6-HKA and provide reference for its pharmacodynamics, DDIs and drug-food interactions studies.

Ginkgo biloba and Its Constituent 6-hydroxykynurenic-acid as well as Its Proanthocyanidins Exert Neurorestorative Effects against Cerebral Ischemia.

Neuroprotective effects against cerebral ischemia/reperfusion (I/R) injury by Ginkgo biloba leaves are commonly attributed to the antioxidant activity of its proanthocyanidins. Furthermore, preliminary experiments identified 6-hydroxykynurenic acid (6-HKA) as a major contributor to this effect of extract of G. biloba leaves (EGb) prepared according to the Chinese Pharmacopoeia (ChP). In order to elucidate the specific contribution of both proanthocyanidins and 6-HKA to the overall neurorestorative effects of this extract according to ChP, EGb ChP was separated into pure 6-HKA and a newly developed Ginkgo proanthocyanidin extract (GPE), enriched in proanthocyanidins but not containing 6-HKA. Male Sprague-Dawley rats were divided into the groups: sham: 8; model (placebo): 25; GPE 80 mg/kg: 13; GPE 40 mg/kg: 13; GPE 20 mg/kg: 16; grape seed extract (negative control) 40 mg/kg: 18; nimodipine (positive control) 2 mg/kg: 8. All non-sham animals were subjected to cerebral I/R injury by occluding the middle cerebral artery with a nylon suture that was removed after 2 h of ischemia to establish reperfusion. For comparison, a parallel series of experiments were performed with 6-HKA. In these in vivo experiments, neurological dysfunctions were reduced by both GPE and 6-HKA, and both average infarct size and concentrations of malondialdehyde (MDA) and super oxide dismutase (SOD) were significantly ameliorated as compared to the model group. This data, therefore, demonstrates that the neuroprotective effects of EGb cannot be explained by a purely chemical antioxidative effect alone as has been previously proposed, especially with regards to the proanthocyanidins. A pharmacological neurorestorative effect of EGb on neurons and brain tissue itself seems to be a much more straightforward explanation for the presented observations. This effect is most likely explained by the synergistic action of both its numerous phenolic constituents (GPE) and 6-hydroxykynurenic acid (6-HKA), which could be identified as one major contributor to the observed activity.

[Similarities and differences between Ginkgo biloba and Panax notoginseng in treatment of ischemic cerebrovascular disease].

Ginkgo biloba and Panax notoginseng are both herb medicines for cerebrovascular disease, and play an active role in treating ischemic cerebrovascular disease(ICVD). Their mechanisms of action include antioxidant stress, nerve protection, vascular protection. According to the comparative study of literatures, G. biloba has a certain protective effect from the early stage of free radical formation throughout the whole process of causing cell inflammation and apoptosis in antioxidant stress; while P. notoginseng has mainly anti-inflammatory, anti-apoptosis effects. In the nerve protection and repair of nerve damage caused by glutamate, both could promote neurogenesis, repair damaged axons and protect nerve cells. In addition, G. biloba could also relieve neurotoxicity caused by glutamate damage, while P. notoginseng have a unique effect in repairing blood-brain barrier(BBB) and blood vessel regeneration. In clinic, they are used as auxiliary drugs in combination with thrombolytic therapy, and play curative effects in alleviating inflammation, eliminating edema, improving the cure rate and the prognosis. For cerebral diseases caused by chronic cerebral hypoperfusion, G. biloba could reduce inflammation and improve cognition. In addition, G. biloba could protect neurocyte by adjusting the secretion of dopamine in vivo, and has a certain effect on antidepressant diseases, which however needs further studies.

Mori Ramulus (Chin.Ph.)-the Dried Twigs of Morus alba L./Part 1: Discovery of Two Novel Coumarin Glycosides from the Anti-Hyperuricemic Ethanol Extract.

In Traditional Chinese Medicine (TCM), Mori ramulus (Chin.Ph.)-the dried twigs of Morus alba L.-is extensively used as an antirheumatic agent and also finds additional use in asthma therapy. As a pathological high xanthine oxidase (XO, EC 1.1.3.22) activity is strongly correlated to hyperuricemy and gout, standard anti-hyperuremic therapy typically involves XO inhibitors like allopurinol, which often cause adverse effects by inhibiting other enzymes involved in purine metabolism. Mori ramulus may therefore be a promissing source for the development of new antirheumatic therapeutics with less side effects. Coumarins, one of the dominant groups of bioactive constituents of M. alba, have been demonstrated to possess anti-inflammatory, antiplatelet aggregation, antitumor, and acetylcholinesterase (AChE) inhibitory activities. The combination of HPLC (DAD) and Q-TOF technique could give excellent separating and good structural characterization abilities which make it suitable to analyze complex multi-herbal extracts in TCM. The aim of this study was to develop a HPLC (DAD)/ESI-Q-TOF-MS/MS method for the identification and profiling of pharmacologically active coumarin glycosides in Mori ramulus refined extracts for used in TCM. This HPLC (DAD)/ESI-Q-TOF-MS/MS method provided a rapid and accurate method for identification of coumarin glycosides-including new natural products described here for the first time-in the crude extract of M. alba L. In the course of this project, two novel natural products moriramulosid A (umbelliferone-6-ß-d-apiofuranosyl-(1→6)-ß-d-glucopyranoside) and moriramulosid B (6-[[6-O-(6-deoxy-α-l-mannopyranosyl)-ß-d-glucopyranosyl]oxy]-2H-1-benzopyran-1-one) were newly discovered and the known natural product Scopolin was identified in M. alba L. for the first time.

HPLC quantification of all five ginkgolic acid derivatives in Ginkgo biloba extracts using 13 : 0 ginkgolic acid as a single marker compound.

An HPLC quantification method for ginkgolic acid derivatives in Ginkgo biloba leaf extracts was developed. Using 13 : 0 ginkgolic acid as a marker compound, the relative correlation factors of the four other ginkgolic acid derivatives - namely, 15 : 0 ginkgolic acid, 15 : 1 ginkgolic acid, 17 : 1 ginkgolic acid, and 17 : 2 ginkgolic acid - to 13 : 0 ginkgolic acid were determined by HPLC and subsequently used for calculating their contents in ten hydro-ethanolic refined extract samples. In other words, the content of 13 : 0 ginkgolic acid in the extracts was determined using the isolated compound as an external standard. Subsequently the now known concentration of this compound functioned as an internal standard for the quantification of the other four ginkgolic acid derivatives via the described correlation factors. This HPLC method was validated by two independent control measurements, one with an external standard for every individual compound and one based on the present method with the single marker compound alone. The results did not differ significantly in any of the 10 tested extract samples. The protocol presented here thus not only uses the same reference substance for G. biloba extracts as the current Chinese Pharmacopoeia method but also incorporates the advantages of the current European Pharmacopoeia approach. It is simple, reproducible, and can be used to determine the total contents of ginkgolic acid derivatives in G. biloba leaf extracts.

Lupane- and Friedelane-Type Triterpenoids from Celastrus stylosus.

Two new triterpenoids, 30-hydroxylup-20(29)-ene 3ß-caffeate (1) and 24-nor-friedelan-6α,10-dihydroxy-1,2-dioxo-4,7-dien-29-oic acid (2), together with eight known compounds 3-10, were isolated from the roots of Celastrus stylosus. The structures of these compounds were elucidated on the basis of spectroscopic analyses. To the best of our knowledge, this represents the first study on the chemical constituents of C. stylosus. The antiproliferative activities of the triterpenoids against six human cancer cell lines (PANC-1, A549, PC-3, HepG2, SGC-7901, and HCCLM3) were evaluated. Compounds 3, 4, and 10 exhibited comparable activities against PC-3 and HCCLM3 cell lines as the positive control taxol.

Exploration of the in vitro Antiviral Effects and the Active Components of Changyanning Tablets Against Enterovirus 71.

Purpose: This study aims to investigate the in vitro antiviral effects of the aqueous solution of Changyanning (CYN) tablets on Enterovirus 71 (EV71), and to analyze its active components. Methods: The in vitro anti-EV71 effects of CYN solution and its herbal ingredients were assessed by testing the relative viral RNA (vRNA) expression level and the cell viability rates. Material basis analysis was performed using HPLC-Q-TOF-MS/MS detection. Potential targets and active components were identified by network pharmacology and molecular docking. The screened components were verified by in vitro antiviral experiments. Results: CYN solution exerted anti-EV71 activities as the vRNA is markedly reduced after treatment, with a half maximal inhibitory concentration (IC50) of 996.85 µg/mL. Of its five herbal ingredients, aqueous extract of Mosla chinensis (AEMC) and leaves of Liquidambar formosana Hance (AELLF) significantly inhibited the intracellular replication of EV71, and the IC50 was tested as 202.57 µg/mL and 174.77 µg/mL, respectively. Based on HPLC-Q-TOF-MS/MS results, as well as the comparison with the material basis of CYN solution, a total of 44 components were identified from AEMC and AELLF. Through network pharmacology, AKT1, ALB, and SRC were identified as core targets. Molecular docking performed between core targets and the components indicated that 21 components may have anti-EV71 effects. Of these, nine were selected for in vitro pharmacodynamic verification, and only rosmarinic acid manifested in vitro anti-EV71 activity, with an IC50 of 11.90 µg/mL. Moreover, rosmarinic acid can stably bind with three core targets by forming hydrogen bonds. Conclusion: CYN solution has inhibitory effects on EV71 replication in vitro, and its active component was identified as rosmarinic acid. Our study provides a new approach for screening and confirmation of the effective components in Chinese herbal preparation.

Quality Evaluation of Shexiang Tongxin Dropping Pill Based on HPLC Fingerprints Combined with HPLC-Q-TOF-MS/MS Method.

Shexiang Tongxin Dropping Pill (STP) is a composite formula of traditional Chinese medicine that is widely used for the treatment of cardiovascular diseases. It consists of seven medicinal extracts thereof or materials, including Bufonis venenum, synthetic Moschus, Panax ginseng, Bovis calculus artifactus, Bear bile powder, Salvia miltiorrhiza Bge and synthetic borneol. However, it is considerably difficult to evaluate the quality of STP due to its complex chemical compositions. This paper was designed to explore a comprehensive and systematic method combining fingerprints and chemical identification for quality assessment of STP samples. Twenty batches of STP samples were analyzed by high-performance liquid chromatography (HPLC) and high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry. Ten common peaks were detected by HPLC fingerprint similarity evaluation system. Meanwhile, 100 compounds belonging to 4 structural characteristics, including 23 bufadienolides, 36 organic acids, 34 saponins and 7 other types, were systematically identified as the basic components in STP. This study could be used for clarifying the multiple bioactive substances and developing a comprehensive quality evaluation method of STP.

The Tandem of Liquid Chromatography and Network Pharmacology for the Chemical Profiling of Pule'an Tablets and the Prediction of Mechanism of Action in Treating Prostatitis.

Prostatitis, a prevalent urinary tract disorder in males, has a complex etiology that leads to severe clinical discomfort. Pule'an Tablets, a classic single-component formulation primarily based on rapeseed pollen, have been clinically proven to have a beneficial therapeutic effect on both prostatitis and benign prostatic hyperplasia. However, there is currently a lack of research on the chemical composition and mechanisms of action of Pule'an Tablets in treating prostatitis. In this study, using liquid chromatography-mass spectrometry (LC-MS), a total of 53 compounds in Pule'an Tablets were identified, including flavonoids, phenylpropionamides, lipids, glucosinolates, and nucleic acids. Subsequently, through a network pharmacology analysis, potential target genes and their mechanisms of action were predicted accordingly. The results suggested that genes such as LPAR5, LPAR6, LPAR4, LPAR3, LPAR2, LPAR1, F2, ENPP2, MMP9, and TNF, along with pathways like prostate cancer, endocrine resistance, bladder cancer, and the IL-17 signaling pathway, may represent potential pathways involved in the therapeutic effects of Pule'an Tablets. This study represents the first systematic investigation into the chemical composition of Pule'an Tablets, shedding light on the potential mechanisms underlying their efficacy in treating prostatitis. These findings could serve as a valuable reference for future pharmacological research on Pule'an Tablets.

Baicalein-corrected gut microbiota may underlie the amelioration of memory and cognitive deficits in APP/PS1 mice.

Background: Baicalein is an active ingredient extracted from the root of S. baicalensis Georgi, which exhibits cardiovascular protection, anti-inflammatory, and anti-microbial properties. Our previous study showed that chronic treatment of Baicalein ameliorated cognitive dysfunction in a mouse model of Alzheimer's disease (AD). However, it remains unknown whether Baicalein ameliorates cognitive deficits in AD mouse models by altering gut microbiota and its metabolites. Methods: Behavioral tests, metagenomic and untargeted metabolomics analyses were used to evaluate the effects of Baicalein on the APP/PS1 mice. Results: Our research showed that treatment of Baicalein for 2 weeks ameliorated cognition and memory in a dose-dependent manner, as indicated by the significant increases in the Discrimination index and Number of crossings and decrease in latency to the previous platform location in 8-month of age APP/PS1 mice in novel object recognition and water maze tests. The metagenomic analysis showed the abundance of the dominant phyla in all groups, including Bacteroidetes (14.59%-67.02%) and Firmicutes (20.19%-61.39%). LEfSe analysis of metagenomics identified three species such as s__Roseburia_sp_1XD42_69, s__Muribaculaceae_bacterium_Isolate_104_HZI, s__Muribaculaceae_bacterium_Isolate_110_HZI as Baicalein-treated potential biomarkers. Metabolite analysis revealed the increment of metabolites, including glutamate, thymine and hexanoyl-CoA. Conclusion: The effects of Baicalein on memory and cognition may relate to the metabolism of nucleotides, lipids and glucose.

Pharmacokinetics and brain distribution studies of 6-hydroxykynurenic acid and its structural modified compounds.

OBJECTIVES: 6-Hydroxykynurenic acid (6-HKA) is an organic acid component in extracts of Ginkgo biloba leaves and acts as a major contributor to neurorestorative effects, while its oral bioavailability was low. Therefore, using prodrug method to improve the bioavailability and brain content of 6-HKA is significant. METHODS: Three structural modified compounds of 6-HKA were synthesized, and ultra performance liquid chromatography-tandem mass spectrometry methods for quantification of these structural modified compounds in rat plasma and rat brain homogenate were established and comprehensively validated. The methods were effectively applied to investigate the effects of structural modification on apparent permeability coefficients in cells, the pharmacokinetics and the brain distribution in rats. KEY FINDINGS: The results illustrated that esterification can greatly improve the apparent permeability coefficient and bioavailability of 6-HKA. Comparing with direct oral administration of 6-HKA, the bioavailability of isopropyl ester was greatly improved (from 3.96 ± 1.45% to 41.8 ± 15.3%), and the contents of 6-HKA in rat brains (49.7 ± 9.2 ng/g brain) were significantly higher after oral administration. CONCLUSIONS: The bioavailability and the brain content of 6-HKA can be improved by the prodrug method. Among three structural modified compounds, isopropyl-esterified 6-HKA was the most promising treatment.

Biology of Peptide Transporter 2 in Mammals: New Insights into Its Function, Structure and Regulation.

Peptide transporter 2 (PepT2) in mammals plays essential roles in the reabsorption and conservation of peptide-bound amino acids in the kidney and in maintaining neuropeptide homeostasis in the brain. It is also of significant medical and pharmacological significance in the absorption and disposing of peptide-like drugs, including angiotensin-converting enzyme inhibitors, ß-lactam antibiotics and antiviral prodrugs. Understanding the structure, function and regulation of PepT2 is of emerging interest in nutrition, medical and pharmacological research. In this review, we provide a comprehensive overview of the structure, substrate preferences and localization of PepT2 in mammals. As PepT2 is expressed in various organs, its function in the liver, kidney, brain, heart, lung and mammary gland has also been addressed. Finally, the regulatory factors that affect the expression and function of PepT2, such as transcriptional activation and posttranslational modification, are also discussed.

Influence of organic anion transporter 1/3 on the pharmacokinetics and renal excretion of ginkgolides and bilobalide.

ETHNOPHARMACOLOGICAL RELEVANCE: The major terpene lactones of ginkgo biloba extract (GBE) include ginkgolide A, B, C and bilobalide are used for the protection of cardiovascular, cerebrovascular and neurodegenerative diseases. Terpene lactones are orally bioavailable and predominantly eliminated via the renal pathway. However, information on the transporters involved in the pharmacokinetics (PK) and renal excretion of terpene lactones is limited. AIM OF THE STUDY: The objective of this study is to assess the role of OAT1/3 which are important transporters in the human kidney in the PK and renal excretion ginkgolide A, B, C and bilobalide. MATERIALS AND METHODS: Uptake of ginkgolide A, B, C and bilobalide in Madin-Darby Canine Kidney (MDCK) and human embryonic kidney 293 (HEK293) cells overexpressing OAT1 or OAT3, respectively were studied. To verify the result from in vitro cell models, the studies on PK, kidney accumulation and urinary excretion of ginkgolide A, B, C and bilobalide were carried out in rats. RESULTS: The result showed that ginkgolide A, B, C and bilobalide are low-affinity substrates of OAT1/3. Following co-administration with probenecid, a typical inhibitor of OAT1/3, the rat plasma concentrations of ginkgolide A, B, C and bilobalide increased significantly. AUC showed a significant increase in the probenecid-treated rats compared to control rats (893.48 vs. 1123.85, 314.91 vs. 505.74, and 2724.97 vs. 3096.40 µg/L*h for ginkgolide A, B and bilobalide, respectively), while the clearance of these compounds significantly decreased. The accumulation of ginkgolide A, B and bilobalide in the kidney of the probenecid-treated rats was reduced by 1.8, 2.4, and 1.5-fold, respectively; further reducing the cumulative urinary recovery of these compounds. CONCLUSION: The findings indicated that ginkgolide A, B and bilobalide are excreted via OAT1/3-mediated transport in the kidney and OAT1/3 inhibitor significantly influence the PK ginkgolides and bilobalide.

Development and validation of a sensitive LC-MS/MS method for the determination of 6-hydroxykynurenic acid in rat plasma and its application to pharmacokinetics study.

A sensitive and specific bioanalytical method of liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the quantification of 6-hydroxykynurenic acid (6-HKA) in a small quantity of rat plasma has been developed and comprehensively validated. Tolbutamide (Tol) was used as the internal standard (IS). An aliquot of 50 µL rat plasma sample was deproteinized by 150 µL methanol, and then 100 µL of its supernatant was mixed with 100 µL water after centrifugation. Chromatographic separation was performed on a ZORBAX Eclipse Plus C18 Rapid Resolution HD column (2.1 mm × 100 mm, 1.8 µm) with a gradient mobile phase consisting of water containing 2 mM ammonium formate and methanol at a flow rate of 0.2 mL/min over a total run time of 5.0 min. The mass spectrometer was operated under multiple reactions monitoring (MRM) mode with the transitions m/z 206.1 → 160.0 for 6-HKA and m/z 269.0 → 170.0 for Tol. The linear range was 2.5-250 ng/mL with the square regression coefficient (r2) of 0.997. The lower limit of quantification (LLOQ) was 2.5 ng/mL (Relative Error, RE +1.6% and RSD 4.8%, n = 5). The intra- and inter-day precision and accuracy was <13.3%. The mean recovery of 6-HKA in rat plasma was between the range of 99.3-103.4%. This method was successfully applied to study the pharmacokinetics of 6-HKA in rats after oral administration at a single dose of 20.0 mg/kg and after tail intravenous injection at a single dose of 2.0 mg/kg. Pharmacokinetic parameters bioavailability, Cmax, oral, Tmax, oral, AUC0-24h, oral, AUC0-∞, oral, AUC0-24h, iv and AUC0-∞, iv were 3.96%, 152.0 ±â€¯85.5 ng/mL, 0.4 ±â€¯0.1 h, 340.0 ±â€¯136.3 ng/mL ∗ h, 369.5 ±â€¯135.0 ng/mL ∗ h, 906.6 ±â€¯324.1 ng/mL*h and 932.9 ±â€¯336.5 ng/mL ∗ h, respectively.