Cu(II)/Vasicine Promoted Intramolecular C-O Formation: Synthesis of Benzoxazoles in EtOH

AIMS AND OBJECTIVES

Benzoxazoles are valuable bicyclic aromatic compounds; the construction of benzoxazoles via C-O cross-coupling reactions has attracted more and more attention.

MATERIALS AND METHODS

The best condition of C-O bond formation from o-haloanilides was carried out, taking Cu(OTf)₂ (5 mol%) and vasicine (10 mol%) as the catalysts in EtOH in the presence of K₂CO₃ (2 eq.) for 12 h at 90°C.

RESULTS

A series of 2-substituted benzoxazoles have been prepared in high yields from 2-bromoanilides and 2- iodioanilides under mild conditions.

CONCLUSION

We have developed an efficient Cu-vasicine catalytic system for intramolecular C-O bond formation. This strategy is applicable to the synthesis of a wide variety of 2-substituted benzoxazoles by intramolecular O-arylation of o-haloanilides.

In vivo and in vitro metabolism and pharmacokinetics of cholinesterase inhibitor deoxyvasicine from aerial parts of Peganum harmala Linn in rats via UPLC-ESI-QTOF-MS and UPLC-ESI-MS/MS

ETHNOPHARMACOLOGICAL RELEVANCE

Aerial parts of Peganum harmala Linn are a Uighur traditional medicinal herb in China used to treat amnesia, bronchial asthma, and cough. Deoxyvasicine (DVAS), a potent cholinesterase inhibitor exhibiting anti-senile dementia activity, is one of the chief active ingredients in aerial parts of P. harmala and plays a key role in mediating the pharmacological effects of P. harmala. However, the metabolic profiling and in vivo pharmacokinetic characteristics of DVAS still remain unknown.

AIM OF THE STUDY

The aim of this present study was to investigate the metabolism and pharmacokinetic properties of DVAS in rats by using ultra-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UPLC-ESI-QTOF-MS) and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-ESI-MS/MS) method.

MATERIALS AND METHODS

The metabolic profiling of DVAS was evaluated in vitro and in vivo by rat liver microsomes (RLMs) incubation and by rat bio-specimens, such as urine, feces, plasma, and bile, after the oral administration of 45 mg/kg DVAS. An efficient and sensitive UPLC-ESI-MS/MS method was developed and validated to simultaneously determine DVAS and its major four metabolites, namely, vasicine, deoxyvasicinone, vasicinone, and 1,2,3,9-tetrahydropyrrolo[2,1-b]quinazolin-3-β-D-glucuronide in rat plasma. For pharmacokinetic studies, 32 Sprague-Dawley rats were randomly divided into four groups, namely, intravenous dosage group (2 mg/kg DVAS) and three oral dosage groups (5, 15, and 45 mg/kg DVAS). In addition, the activity of the components in plasma after intravenous administration of DVAS was evaluated by in vitro anti-butyrylcholinesterase (BChE) assays.

RESULTS

A total of 23 metabolites were found in RLMs, plasma, urine, feces, and bile by UPLC-ESI-QTOF-MS. The metabolic pathway of DVAS in vivo and in vitro mainly involved hydroxylation, dehydrogenation, acetylation, methylation, glucuronidation, and O-sulphate conjugation, and the C-3 and C-9 sites were the main metabolic soft spots. All 23 metabolites were detected in the urine sample, and 13, 8, 22, and 6 metabolites were identified from rat feces, plasma, bile, and RLMs, respectively. The standard curves of DVAS and four metabolites in rat plasma showed good linearity in the concentration range of 0.82-524.00 ng/mL with acceptable selectivity, precision, accuracy, recovery, and stability. DVAS exhibited linear dose-proportional pharmacokinetics at doses of 5, 15, and 45 mg/kg after oral administration, and the average oral absolute bioavailability of DVAS was 47.46%. The in vitro anti-BChE assays implied that the inhibitive activities were mainly due to the different concentrations of prototype DVAS.

CONCLUSIONS

DVAS can be rapidly absorbed and excreted by blood, and it is also extensively metabolized in vivo, and the anti-BChE activity in blood is mainly attributed to DVAS. These findings can lay a foundation for new drug development for DVAS.

Stereoselective glucuronidation metabolism, pharmacokinetics, anti-amnesic pharmacodynamics, and toxic properties of vasicine enantiomers in vitro and in vivo

Vasicine (VAS) is a potential natural cholinesterase inhibitor for treatment of Alzheimer's disease. Due to one chiral centre (C-3) presenting in molecule, VAS has two enantiomers, d-vasicine (d-VAS) and l-vasicine (l-VAS). The study was undertaken to investigate the stereoselective glucuronidation metabolism, pharmacokinetics, anti-amnesic effect and acute toxicity of VAS enantiomers. In results, the glucuronidation metabolic rate of l-VAS was faster than d-VAS in human liver microsomes and isoenzymes tests, and it was proved that the UDP-glucuronosyltransferase (UGT) 1A9 and UGT2B15 were the major metabolic enzymes for glucuronidation of l-VAS, while only UGT1A9 for d-VAS, which take responsibility of the significantly less metabolic affinity of d-VAS than l-VAS in HLM and rhUGT1A9. The plasma exposure of d-VAS in rats was 1.3-fold and 1.6-fold higher than that of l-VAS after intravenous and oral administration of d-VAS and l-VAS, respectively. And the plasma exposure of the major glucuronidation metabolite d-VASG was one of tenth of l-VASG or more less, no matter by intravenous or oral administration. Both d-VAS and l-VAS were exhibited promising acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities, and the BChE inhibitory activity of d-VAS with IC₅₀ of 0.03 ± 0.001 μM was significantly stronger than that of l-VAS with IC₅₀ of 0.98 ± 0.19 μM. The molecular docking results indicated that d-VAS and l-VAS could bind to the catalytic active site (CAS position) either of human AChE and BChE, and the BChE combing ability of d-VAS (the score of GBI/WAS dG -7.398) was stronger than that of l-VAS (the score of GBI/WAS dG -7.135). Both d-VAS and l-VAS could improving the learning and memory on scopolamine-induced memory deficits in mice. The content of acetylcholine (ACh) after oral administration d-VAS increased more than that of l-VAS in mice cortex, through inhibiting cholinesterase (ChE) and increasing choline acetyltransferase (ChAT). In addition, the LD₅₀ value of d-VAS (282.51 mg·kg^-1) was slight lower than l-VAS (319.75 mg·kg^-1). These results indicated that VAS enantiomers displayed significantly stereoselective metabolic, pharmacokinetics, anti-amnesic effect and toxic properties in vitro and in vivo. The d-VAS might be the dominant configuration for treating Alzheimer's disease.

Determination of the phytochemical composition of Jingning fang and the in vivo pharmacokinetics of its metabolites in rat plasma by UPLC-MS/MS

Jingning fang (JNF) is an effective Traditional Chinese Medicine (TCM) which is used for the treatment of Attention Deficit Hyperactivity Disorder (ADHD). To clarify the bioactive constituents of JNF, a Thermo Q Exactive™ Plus Orbitrap™ mass spectrometer was used in this study. More than 127 chemical compounds were isolated and identified tentatively in the JNF extract, while 42 prototype constituents with 4 potential metabolites were identified tentatively in rat plasma. A method for simultaneous determination of polygalaxanthone III (PAIII), sibiricose A5 (A5), sibiricose A6 (A6), 3, 6'-disinapoyl sucrose (3,6'-DISS), tenuifoliside C (TEC), tenuifolin B (TNB), verbascoside (VCE), heterophyllin B (HEB) and schisandrin (SCH) in rat was developed and validated using polydatin (PLN) and psoralen (PSN) as internal standards. All calibration curves proved favorable linearity (R2≥0.9923) in linear ranges. The lower limit of quantification (LLOQ) was 2.5ng/mL for PAIII, A5, 3, 6'-DISS, TNB, VCE, HEB and SCH, 1.0ng/mL for A6 and TEC, respectively. Intra-day and inter-day precisions didn't exceed 14.0% for all the analytes. Extraction recoveries and matrix effects of analytes and IS were acceptable. The validated method has been successfully applied to the pharmacokinetics (PK) studies of the nine compounds in JNF. These findings are useful for predicting the bioactive components of JNF, and will aid in optimizing dose regimens of the drug.

Anti-amnesic effect of extract and alkaloid fraction from aerial parts of Peganum harmala on scopolamine-induced memory deficits in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Aerial parts of Peganum harmala Linn (APP) is used as traditional medical herb for treatment of forgetfulness in Uighur medicine in China. But, the active ingredients and underlying mechanisms are unclear.

AIM OF THE STUDY

The present study was undertaken to investigate the improvement effects of extract and alkaloid fraction from APP on scopolamine-induced cognitive dysfunction and to elucidate their underlying mechanisms of action, and to support its folk use with scientific evidence, and lay a foundation for its further researches.

MATERIALS AND METHODS

The acetylcholinesterase (AChE) inhibitory activities of extract (EXT), alkaloid fraction (ALK) and flavonoid fraction (FLA) from APP were evaluated in normal male C57BL/6 mice. The anti-amnesic effects of EXT and ALK from APP were measured in scopolamine-induced memory deficits mice by the Morris water maze (MWM) tasks. The levels of biomarkers, enzyme activity and protein expression of cholinergic system were determined in brain tissues.

RESULTS

The AChE activity was significantly decreased and the content of neurotransmitter acetylcholine (ACh) was significantly increased in normal mice cortex and hippocampus by treatment with donepezil at dosage of 8mg/kg, EXT at dosages of 183, 550, 1650mg/kg and ALK at dosages of 10, 30, 90mg/kg (P<0.05), and the AChE activity and the content of ACh were not significantly changed in cortex and hippocampus after treatment with FLA at dosages of 10, 30, 90mg/kg (P>0.05). In the MWM task, scopolamine-induced a decrease in both the swimming time within the target zone and the number of crossings where the platform had been placed were significantly reversed by treatment with EXT at dosages of 550, 1650mg/kg and ALK at dosages of 30, 90mg/kg (P<0.05). Moreover, the activity and protein expression of AChE was significantly decreased and the content of neurotransmitter ACh was significantly increased in cerebral cortex of scopolamine-induced mice by treatment with EXT at dosages of 183, 550, 1650mg/kg and ALK at dosages of 10, 30, 90mg/kg (P<0.05), compared with scopolamine-treated group.

CONCLUSIONS

EXT and ALK from APP exert beneficial effect on learning and memory processes in mice with scopolamine-induced memory impairment. APP is an effective traditional folk medicine and the ALK fraction is proved to be the main effective components for the treatment of forgetfulness. The ALK may be valuable source for lead compounds discovery and drug development for treatment of memory impairment such as in Alzheimer's disease.

A review on traditional uses, phytochemistry, pharmacology, pharmacokinetics and toxicology of the genus Peganum

ETHNOPHARMACOLOGICAL RELEVANCE

The plants of the genus Peganum have a long history as a Chinese traditional medicine for the treatment of cough, hypertension, diabetes, asthma, jaundice, colic, lumbago, and many other human ailments. Additionally, the plants can be used as an amulet against evil-eye, dye and so on, which have become increasingly popular in Asia, Iran, Northwest India, and North Africa.

AIM OF THE REVIEW

The present paper reviewed the ethnopharmacology, phytochemistry, analytical methods, biological activities, metabolism, pharmacokinetics, toxicology, and drug interaction of the genus Peganum in order to assess the ethnopharmacological use and to explore therapeutic potentials and future opportunities for research.

MATERIALS AND METHODS

Information on studies of the genus Peganum was gathered via the Internet (using Google Scholar, Baidu Scholar, Elsevier, ACS, Pudmed, Web of Science, CNKI and EMBASE) and libraries. Additionally, information was also obtained from some local books, PhD and MS's dissertations.

RESULTS

The genus Peganum has played an important role in traditional Chinese medicine. The main bioactive metabolites of the genus include alkaloids, flavonoids, volatile oils, etc. Scientific studies on extracts and formulations revealed a wide range of pharmacological activities, such as cholinesterase and monoamine oxidase inhibitory activities, antitumor, anti-hypertension, anticoagulant, antidiabetic, antimicrobial, insecticidal, antiparasidal, anti-leishmaniasis, antioxidant, and anti-inflammatory.

CONCLUSIONS

Based on this review, there is some evidence for extracts' pharmacological effects on Alzheimer's and Parkinson's diseases, cancer, diabetes, hypertension. Some indications from ethnomedicine have been confirmed by pharmacological effects, such as the cholinesterase, monoamine oxidase and DNA topoisomerase inhibitory activities, hypoglycemic and vasodilation effects of this genus. The available literature showed that most of the activities of the genus Peganum can be attributed to the active alkaloids. Data regarding many aspects of the genus such as mechanisms of actions, metabolism, pharmacokinetics, toxicology, potential drug interactions with standard-of-care medications is still limited which call for additional studies particularly in humans. Further assessments and clinical trials should be performed before it can be integrated into medicinal practices.

Peganumine B-I and two enantiomers: new alkaloids from the seeds of Peganum harmala Linn. and their potential cytotoxicity and cholinesterase inhibitory activities

Ten new alkaloids (peganumine B-I and two enantiomers), containing five β-carbolines, three quinazolones, two compounds with both of the above skeletons, and one amphoteric alkaloid with a four-membered ring, were isolated from Peganum harmala.