Determination of Stachydrine and Leonurine in Herba Leonuri and Its Succedaneum—Herba Lagopsis—with a Sensitive HPLC–MS/MS Method

Natural products in drug discovery and development: Synthesis and medicinal perspective of leonurine

Natural products, those molecules derived from nature, have been used by humans for thousands of years to treat ailments and diseases. More recently, these compounds have inspired chemists to use natural products as structural templates in the development of new drug molecules. One such compound is leonurine, a molecule isolated and characterized in the tissues of Herb leonuri. This molecule has received attention from scientists in recent years due to its potent anti-oxidant, anti-apoptotic, and anti-inflammatory properties. More recently researchers have shown leonurine to be useful in the treatment of cardiovascular and nervous system diseases. Like other natural products such as paclitaxel and artemisinin, the historical development of leonurine as a therapeutic is very interesting. Therefore, this review provided an overview of natural product discovery, through to the development of a potential new drug. Content will summarize known plant sources, the pathway used in the synthesis of leonurine, and descriptions of leonurine’s pharmacological properties in mammalian systems.

TLC-MS identification of alkaloids in Leonuri Herba and Leonuri Fructus aided by a newly developed universal derivatisation reagent optimised by the response surface method

INTRODUCTION

Dragendorff's reagent has low sensitivity and non-specificity for some alkaloids. A new alkaloid derivatisation reagent has been developed and optimised by using a Box-Behnken design method. This new reagent is applicable for structurally diverse natural alkaloids, and is proposed as a universal alkaloid staining reagent.

OBJECTIVE

To establish an efficient and sensitive thin-layer chromatography (TLC) identification method for Leonuri Herba and Leonuri Fructus to characterise their differences and similarities.

METHOD

Three key components (bismuth subnitrate, potassium iodide and iodine) in the derivatisation reaction were re-constructed and optimised using a response surface method. Different inorganic acids, essential additives of the staining reaction, were compared by a single-factor experiment design.

RESULTS

This newly optimised reagent for alkaloids reported in this study, named the enhanced Dragendorff-Wagner's reagent, is composed of 0.82% bismuth subnitrate, 11.1% potassium iodide and 0.76% iodine in 38% phosphoric acid solution. Validation results indicate that the TLC spot of stachydrine stained with the enhanced Dragendorff-Wagner's reagent had a limit of detection of 2.0 μg, good intra- and inter-plate, and intra- and intra-day precisions with relative standard devition values less than 5.0%, and stability over 90 min.

CONCLUSION

This enhanced Dragendorff-Wagner's reagent was applied for TLC identification of 16 reference alkaloids representing 11 structural skeletons, and two closely related herbs (Leonuri Herba and Leonuri Fructus). This newly enhanced Dragendorff-Wagner's reagent is a universal, effective, and sensitive staining reagent for alkaloids.

Chemical Fingerprint Analysis and Ultra-Performance Liquid Chromatography Quadrupole Time-of-Flight Mass Spectrometry-Based Metabolomics Study of the Protective Effect of Buxue Yimu Granule in Medical-Induced Incomplete Abortion Rats

Medical abortion is a common method to terminate an early pregnancy and often causes serious complications such as abnormal uterine bleeding and endometritis. Buxue Yimu granule (BYG) is a well-known traditional Chinese medicine prescription composed of five kinds of drugs and is widely used in gynecology and obstetrics. The aim of the present study was to establish the quality standard of BYG and investigate its protective effect on incomplete abortion. The chemical fingerprint of BYG was established by high performance liquid chromatography (HPLC). The major compounds of BYG were determined by ultra-performance liquid chromatography with triple quadrupole mass spectrometry. An incomplete abortion rat model was induced by intragastric administration of mifepristone (8.3 mg·kg^-1) combined with misoprostol (100.0 μg·kg^-1) during early pregnancy. The serum levels of human chorionic gonadotrophin (HCG), estradiol (E₂), and progesterone (PG) were determined. The serum endogenous metabolites were analyzed by ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS). Multivariate analysis, including partial least squares discriminant analysis (PLS-DA) and orthogonal partial least squares discriminant analysis (OPLS-DA), was employed to analyze the metabolic profiles, and MetaboAnalyst was used to investigate the metabolic pathways. Furthermore, hematoxylin-eosin staining (HE) was used to evaluate the histopathological changes in uterine tissue. The expression levels of VEGFA and NF-κB were detected by immunohistochemistry. The results indicated that HPLC fingerprint analysis can be successfully used to assess the quality of BYG. The medical-induced incomplete abortion rats were clearly separated from control rats, and the biochemical changes were gradually restored to normal after administration of BYG. Moreover, 19 potential biomarkers, including N-lactoylleucine, 2-piperidinone, isobutyryl-l-carnitine, eicosapentaenoylcholine, LysoPC(14:0), LysoPC(20:5), physagulin C, LysoPC(18:3), leukotriene D5, deoxycholic acid 3-glucuronide, glycine, pregnanediol 3-O-glucuronide, LysoPC(18:2), LysoPC(17:0/0:0), N-acetyl-leukotriene E4, LysoPC(18:0), platelet-activating factor, LysoPA(24:1), and LysoPC(18:1), which were mainly related to the amino acids metabolism, lipids metabolism, and bile acid biosynthesis, were identified. Consequently, BYG exerts a potential protective role in the intervention of incomplete abortion by anti-inflammatory, promote endometrial repair, and regulate the metabolic disorders.

Comparative analysis of the main active constituents from different parts of Leonurus japonicus Houtt. and from different regions in China by ultra-high performance liquid chromatography with triple quadrupole tandem mass spectrometry

A rapid, sensitive and convenient analytical method of ultra-performance liquid chromatography coupled with triple-quadrupole linear ion-trap tandem mass spectrometry (UPLC-QTRAP®/MS²) was proposed for the simultaneous determination of characteristic alkaline and acidic components covering many structure types including alkaloids, phenolic acids, phenylpropanoids and flavonoids in Leonurus japonicus Houtt. (LJ). The proposed method was first reported and validated by assessing the matrix effects, linearity, limit of detections, limit of quantifications, precision, repeatability, stability and recovery of target components. The developed UPLC-QTRAP®/MS² was successfully applied to simultaneously determine all target compounds in 38 batches of LJ from 11 different producing regions in China and five organs (including root, caulis, branch, flower and leaf) of LJ from the same stand planting base in Jiangsu Province (China). The result showed that LJ in different regions with different geographical position would affect the accumulation of different compounds, and the significant discrepancies of some target compounds were also observed in different organs of LJ due to different biosynthetic pathway and enzymes in different organs. Furthermore, both hierarchical clustering analysis and principal components analysis were performed to classify the 38 batches of LJ samples from different producing regions on the basis of target compounds. As a result, the samples could be mainly clustered into different groups, which were similar with areas classification. Overall, the presented method would be helpful for the comprehensive utilization and development of LJ resources.

Novel Agmatine Derivatives in Maerua edulis With Bioactivity Against Callosobruchus maculatus, a Cosmopolitan Storage Insect Pest

Food security in developing countries is threatened by crop pests and ectoparasites in livestock. Strategies for their management still rely on synthetic pesticides which are not always effective and the active ingredients persist in the environment with negative consequences for beneficial arthropods, farmers and consumers, hence necessitating research on sustainable alternatives. Botanical insecticides are increasingly relevant, typically having lower impacts on users, consumers and the environment. One example is the southern African shrub the Blue bush-berry, Maerua edulis. Recent work reported effective pest control using this plant species against cattle ticks, storage beetles and vegetable pests. However, little is known about the chemistry underlying activity and this is essential to optimize its use. Here, we identified two novel plant chemical structures, the E and Z isomers of cinnamoyl-4-aminobutylguanidine along with the E and Z isomers of 4-hydroxycinnamoyl-4-aminobutylguanidine in the leaves of M. edulis. We isolated these compounds from the leaves and elucidated their chemical structures using various spectroscopic techniques including High Resolution Mass Spectrometry and Nuclear Magnetic Resonance Spectroscopy. We also identified a further 11 closely related structures of which 6 are tentatively reported here for the first time. Stachydrine and 3-hydroxystachydrine were also identified in the leaf extract, and occurred at very high concentrations; up to 2% w/w of dry leaves. We tested these two compounds, along with the 4 main cinnamoylamides and the crude M. edulis leaf extract against the cowpea bruchid Callosobruchus maculatus at concentrations equivalent to those present in extracts used by smallholder farmers. Mortality of insects exposed to crude plant extracts after 72 h was significantly higher than the untreated control although still lower than for insects exposed to rotenone, the positive control. The two new compounds and stachydrine showed similar activity to the crude extracts suggesting that these compounds explained the activity of the extract. After 6 days, the mortality of insects exposed to crude extracts and isolated compounds was similar to that recorded with the positive control. The stachydrine fraction and the E and Z isomers of cinnamoyl-4-aminobutylguanidine also inhibited oviposition activity in fecund female beetles. Our data show that methanol extracts of M. edulis were toxic to C. maculatus and inhibited oviposition even at 0.1% w/v so these foliar chemicals may explain the activity of the plant material. We also synthesized the amides which facilitated structural elucidation, produced adequate quantities for testing and demonstrated the potential for commercial synthesis.