Structural characterization of monoterpene indole alkaloids in ethanolic extracts of Rauwolfia species by liquid chromatography with quadrupole time-of-flight mass spectrometry

Microbial allies: exploring fungal endophytes for biosynthesis of terpenoid indole alkaloids

Terpenoid indole alkaloids (TIAs) are natural compounds found in medicinal plants that exhibit various therapeutic activities, such as antimicrobial, anti-inflammatory, antioxidant, anti-diabetic, anti-helminthic, and anti-tumor properties. However, the production of these alkaloids in plants is limited, and there is a high demand for them due to the increasing incidence of cancer cases. To address this research gap, researchers have focused on optimizing culture media, eliciting metabolic pathways, overexpressing genes, and searching for potential sources of TIAs in organisms other than plants. The insufficient number of essential genes and enzymes in the biosynthesis pathway is the reason behind the limited production of TIAs. As the field of natural product discovery from biological species continues to grow, endophytes are being investigated more and more as potential sources of bioactive metabolites with a variety of chemical structures. Endophytes are microorganisms (fungi, bacteria, archaea, and actinomycetes), that exert a significant influence on the metabolic pathways of both the host plants and the endophytic cells. Bio-prospection of fungal endophytes has shown the discovery of novel, high-value bioactive compounds of commercial significance. The discovery of therapeutically significant secondary metabolites has been made easier by endophytic entities' abundant but understudied diversity. It has been observed that fungal endophytes have better intermediate processing ability due to cellular compartmentation. This paper focuses on fungal endophytes and their metabolic ability to produce complex TIAs, recent advancements in this area, and addressing the limitations and future perspectives related to TIA production.

Chemical composition and antioxidant activity of the Amazonian fruit Ambelania acida Aubl

Aqueous and hydroalcoholic extracts from the pulp of Ambelania acida Aubl. (Apocynaceae) fruits were subjected to analysis through UHPLC-HRMS and antioxidant potential using the TPC, DPPH, ABTS, FRAP, and ORAC assays. A putative identification of the compounds carried out by comparison of the fragmentation spectra revealed the predominance of the monoterpene indole alkaloids tabersonine, pseudocopsinine, ajmalicine, and strictosidine. Additionally, gallic acid, caffeic acid, citric acid, 3-O-p-coumaroylquinic acid, chlorogenic acid, catechin, ellagic acid, eschweilenol C (ellagic acid deoxyhexoside), and sucrose were identified. In face of the phenolic compounds observed, hydroalcoholic extract showed a higher antioxidant activity compared to the aqueous extract, observed at TPC (108.85 mg GAE/100g), FRAP (0.73 µmol Fe2SO4/g), DPPH (1221.76 µmol TE/g), ABTS (3460.00 µmol TE/g), and ORAC assays (120.47 µmol TE/g). These findings underscore the abundant presence of bioactive compounds, including phenolics and alkaloids, in an edible Amazonian fruit.

Biosynthesis of natural and halogenated plant monoterpene indole alkaloids in yeast

Monoterpenoid indole alkaloids (MIAs) represent a large class of plant natural products with marketed pharmaceutical activities against a wide range of indications, including cancer, malaria and hypertension. Halogenated MIAs have shown improved pharmaceutical properties; however, synthesis of new-to-nature halogenated MIAs remains a challenge. Here we demonstrate a platform for de novo biosynthesis of two MIAs, serpentine and alstonine, in baker's yeast Saccharomyces cerevisiae and deploy it to systematically explore the biocatalytic potential of refactored MIA pathways for the production of halogenated MIAs. From this, we demonstrate conversion of individual haloindole derivatives to a total of 19 different new-to-nature haloserpentine and haloalstonine analogs. Furthermore, by process optimization and heterologous expression of a modified halogenase in the microbial MIA platform, we document de novo halogenation and biosynthesis of chloroalstonine. Together, this study highlights a microbial platform for enzymatic exploration and production of complex natural and new-to-nature MIAs with therapeutic potential.

UPLC-ESI-QTOF-MS assisted targeted metabolomics to study the enrichment of vinca alkaloids and related metabolites in Catharanthus roseus plants grown under controlled LED environment

Enrichment of pharmaceutically important vinca alkaloids, vinblastine and vincristine, in the leaves of Madagascar periwinkle (Catharanthus roseus) plants through different pre- or postharvest treatments or cultivation conditions, e.g., exposing the plants to UV-irradiation, has been in focus for decades. Controlled LED environment in the visible light range offers the possibility of monitoring the changes in the concentration of metabolites in the vinca alkaloid-related pathway without involving UV-related abiotic stress. In the frame of our targeted metabolomics approach, 64 vinca alkaloids and metabolites were screened with the help of a UPLC-ESI-QTOF-MS instrumental setup from the leaf extracts of C. roseus plants grown in chambers under control (medium light), low light, and high blue / high red/ high far-red conditions. Out of the 14 metabolites that could be assigned either unambiguously with authentic standards or tentatively with high resolution mass spectrometry-based methods, all three dimer vinca alkaloids, that is, 3',4'-anhydrovinblastine, vinblastine and vincristine showed an at least nine-fold enrichment under high blue irradiation when compared with the control conditions: final concentrations of 961 mg kg-1 dry weight, 33.8 mg kg-1 dry weight, and 11.7 mg kg-1 dry weight could be achieved, respectively. As supported by multivariate statistical analysis, the key metabolites of the vinca alkaloid pathway were highly represented among the metabolites that were specifically stimulated by high blue light application.

Targeted quantitative analysis of monoterpenoid indole alkaloids in Alstonia scholaris by ultra-high-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry

Monoterpene indole alkaloids exhibit structural diversity in herbal resources and have been developed as promising drugs owing to their significant biological activities. Confidential identification and quantification of monoterpene indole alkaloids is the key to quality control of target plants in industrial production but has rarely been reported. In this study, quantitative performance of three data acquisition modes of ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry including full scan, auto-MS2 and target-MS2 , was evaluated and compared for specificity, sensitivity, linearity, precision, accuracy, and matrix effect using five monoterpene indole alkaloids (scholaricine, 19-epi-scholaricine, vallesamine, picrinine, and picralinal). Method validations indicated that target-MS2 mode showed predominant performance for simultaneous annotation and quantification of analytes, and was then applied to determine monoterpene indole alkaloids in Alstonia scholaris (leaves, barks) after extraction procedures optimization using Box-Behnken design of response surface methodology. The variations of A. scholaris monoterpene indole alkaloids in different plant parts, harvest periods, and post-handling processes, were subsequently investigated. The results indicated that target-MS2 mode could improve the quantitative capability of ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry for structure-complex monoterpene indole alkaloids in herbal matrices. Alstonia scholaris, monoterpene indole alkaloids, quadrupole time of flight mass spectrometry, qualitative and quantitative analysis, ultra-high-performance liquid chromatography.

Spatial localization of monoterpenoid indole alkaloids in Rauvolfia tetraphylla by high resolution mass spectrometry imaging

Monoterpenoid indole alkaloids (MIAs) are a large group of biosynthetic compounds, which have pharmacological properties. One of these MIAs, reserpine, was discovered in the 1950s and has shown properties as an anti-hypertension and anti-microbial agent. Reserpine was found to be produced in various plant species within the genus of Rauvolfia. However, even though its presence is well known, it is still unknown in which tissues Rauvolfia produce reserpine and where the individual steps in the biosynthetic pathway take place. In this study, we explore how matrix assisted laser desorption ionization (MALDI) and desorption electrospray ionization (DESI) mass spectrometry imaging (MSI) can be used in the investigation of a proposed biosynthetic pathway by localizing reserpine and the theoretical intermediates of it. The results show that ions corresponding to intermediates of reserpine were localized in several of the major parts of Rauvolfia tetraphylla when analyzed by MALDI- and DESI-MSI. In stem tissue, reserpine and many of the intermediates were found compartmentalized in the xylem. For most samples, reserpine itself was mainly found in the outer layers of the sample, suggesting it may function as a defense compound. To further confirm the place of the different metabolites in the reserpine biosynthetic pathway, roots and leaves of R. tetraphylla were fed a stable-isotope labelled version of the precursor tryptamine. Subsequently, several of the proposed intermediates were detected in the normal version as well as in the isotope labelled versions, confirming that they were synthesized in planta from tryptamine. In this experiment, a potential novel dimeric MIA was discovered in leaf tissue of R. tetraphylla. The study constitutes to date the most comprehensive spatial mapping of metabolites in the R. tetraphylla plant. In addition, the article also contains new illustrations of the anatomy of R. tetraphylla.

Three new oxygenated yohimbane-type alkaloids from Ophiorrhiza japonica

A series of oxygenated yohimbane alkaloids, including three new compounds, ophiorrhines H-J (1-3), and seven known compounds, were isolated from the aerial parts of Ophiorrhiza japonica. The structures with absolute configurations were elucidated by extensive MS and NMR spectroscopic methods, as well as the single crystal X-ray diffraction and ECD calculations. Ophiorrhines H (1) and I (2) represent key oxygenated intermediates in the formation of aromatic ring E in the demethoxycarbonyl-3,14-dihydrogambirtannine (10). Ophiorrhine J (3) is a highly oxidized yohimbane derivative with the planar superconjugated system. The cytotoxic activities of all alkaloids against five human cancer cell lines were evaluated.

Strategy for the quality control of herbal preparations made of Sarcocephalus latifolius: Development and validation of a UHPLC-PDA method for quantification of angustoline and strictosamide and chemical profiling using LC-QToF

INTRODUCTION

Sarcocephalus latifolius is one of the most used plants in West African traditional medicine to treat malaria.

OBJECTIVE

The aim is to establish a strategy to control the quality of herbal preparations made from S. latifolius.

METHOD

A UHPLC-PDA method was developed for the determination and quantification of the two main bioactive compounds (angustoline and strictosamide) in various parts of the plant. Additionally, an LC-QToF with electrospray ionization method is described for the identification and confirmation of compounds in samples of different parts of the plant.

RESULTS

With the UHPLC-PDA method, separation was achieved within 5 min using a C18 column stationary phase at a temperature of 45°C and a gradient system with a mobile phase of water and acetonitrile, both containing 0.1% formic acid. The method was validated for linearity, accuracy, precision (repeatability and intermediate precision), limit of detection (LOD), and limit of quantification (LOQ). The LOD and LOQ of angustoline were found to be 0.3 and 0.8 μg/ml, respectively, and those of strictosamide were found to be 0.1 and 0.3 μg/ml, respectively. Using the LC-QToF method, 90 secondary metabolites, including four isolated compounds from the plant's roots, were identified from leaf, bark, and root samples of S. latifolius.

CONCLUSION

This work is the first to propose a strategy to control the quality of herbal preparations made from S. latifolius. The developed method allows the quantification of the main bioactive compounds and the established chemical profile allows to distinguish the plant from any other species.

Integrated serum pharmacochemistry and investigation of the anti-gastric ulcer effect of Zuojin pill in rats induced by ethanol

CONTEXT

Zuojin Pill (ZJP) has been used to treat gastrointestinal problems in China for hundreds of years.

OBJECTIVE

To discover more potential active ingredients and evaluate the gastroprotective mechanisms of ZJP.

MATERIALS AND METHODS

An approach involving UPLC-Q-Orbitrap HRMS and serum pharmacochemistry was established to screen the multiple chemical constituents of ZJP. Male Sprague-Dawley (SD) rats were divided into six groups: normal control, ulcer control, omeprazole (30 mg/kg), and three ZJP groups (1.0, 2.0 and 4.0 g/kg). After oral treatment with ZJP or omeprazole for 7 days, all groups except the normal control group were orally administered 5 mL/kg ethanol to induce gastric ulceration. Histopathological assessment of gastric tissue was performed by haematoxylin and eosin staining. Antioxidant parameters and inflammatory mediators were determined using ELISA Kit and immunohistochemical analysis.

RESULTS

Ninety components were identified in ZJP. Among them, 23 prototypes were found in rat serum after oral administration of ZJP. The ulcer inhibition was over 90.0% for all the ZJP groups. Compared with the ulcer control rats, ZJP (4.0 g/kg) enhanced the antioxidant capacity of gastric tissue: superoxide dismutase (1.33-fold), catalase (2.61-fold), glutathione (2.14-fold), and reduced the malondialdehyde level (0.48-fold). Simultaneously, the ZJP meaningfully lowered the content of tumour necrosis factor-α (0.76-fold), interleukin-6 (0.66-fold), myeloperoxidase (0.21-fold), and nuclear factor kappa B (p65) (0.62-fold).

DISCUSSION AND CONCLUSIONS

This study showed ZJP could mitigate ethanol-induced rat gastric ulcers, which might benefit from the synergistic actions of multiple ingredients. The findings could support the quality control and clinical trials of ZJP.

A literature perspective on the pharmacological applications of yohimbine

Introduction: Phytochemicals have garnered much attention because they are useful in managing several human diseases. Yohimbine is one such phytochemical with significant pharmacological potential and could be exploited for research by medicinal chemists. It is an indole alkaloid obtained from various natural/synthetic sources.Aims and Results: The research on yohimbine started early, and its use as a stimulant and aphrodisiac by humans has been reported for a long time. The pharmacological activity of yohimbine is mediated by the combined action of the central and peripheral nervous systems. It selectively blocks the pre and postsynaptic α₂-adrenergic receptors and has a moderate affinity for α1 and α2 subtypes. Yohimbine also binds to other behaviourally relevant monoaminergic receptors in the following order: α-2 NE > 5HT-1A>, 5HT-1B > 1-D > D3 > D2 receptors.Conclusion: The current review highlights some significant findings that contribute to developing yohimbine-based drugs. It also highlights the therapeutic potential of yohimbine against selected human diseases. However, further research is recommended on the pharmacokinetics, molecular mechanisms, and drug safety requirements using well-designed randomized clinical trials to produce yohimbine as a pharmaceutical agent for human use.Key MessagesYohimbine is a natural indole alkaloid with significant pharmacological potential.Humans have used it as a stimulant and aphrodisiac from a relatively early time.It blocks the pre- and postsynaptic α2-adrenergic receptors that could be exploited for managing erectile dysfunction, myocardial dysfunction, inflammatory disorders, and cancer.

Genus Rauvolfia: A review of its ethnopharmacology, phytochemistry, quality control/quality assurance, pharmacological activities and clinical evidence

ETHNOPHARMACOLOGICAL RELEVANCE

The plants are from the genus Rauvolfia Plum. ex L. (Apocynaceae), which is represented by 74 species with many synonyms, and distributed worldwide, especially in the Asian, and African continents. Traditionally, some of them are used for the treatment of various disorders related to the central nervous system (CNS), cardiovascular diseases (CVD), and as an antidote due to the presence of monoterpene indole alkaloids (MIAs) such as ajmaline (144), ajmalicine (164) serpentine (182), yohimbine (190) and reserpine (214).

AIM

The present review provides comprehensive summarization and critical analysis of the traditional to modern applications of Rauvolfia species, and the major focus was to include traditional uses, phytochemistry, quality control, pharmacological properties, as well as clinical evidence that may be useful in the drug discovery process.

MATERIALS AND METHODS

Information related to traditional uses, chemical constituents, separation techniques/analytical methods, and pharmacological properties of the genus Rauvolfia were obtained using electronic databases such as Web of Science, Scopus, SciFinder, PubMed, PubChem, ChemSpider, and Google Scholar between the years 1949-2021. The scientific name of the species and its synonyms were checked with the information of The Plant List.

RESULTS

A total of seventeen Rauvolfia species have been traditionally explored for various therapeutic applications, out of which the roots of R. serpentina and R. vomitoria are used most commonly for the treatment of many diseases. About 287 alkaloids, seven terpenoids, nine flavonoids, and four phenolic acids have been reported in different parts of the forty-three species. Quality control (QC)/quality assurance (QA) of extracts/herbal formulations of Rauvolfia species was analyzed by qualitative and quantitative methods based on the major MIAs such as compounds 144, 164, 182, 190, and 214 using HPTLC, HPLC, and HPLC-MS. The various extracts of different plant parts of thirteen Rauvolfia species are explored for their pharmacological properties such as antimicrobial, antioxidant, antiprotozoal, antitrypanosomal, antipsychotic, cardioprotective, cholinesterase inhibitory, and hepatoprotective. Of which, clinical trials of herbal formulations/extracts of R. serpentina and MIAs have been reported for CVD, CNS, antihypertensive therapy, antidiabetic effects, and psoriasis therapy, while the extracts and phytoconstituents of remaining Rauvolfia species are predominantly significant, owning them to be additional attention for further investigation under clinical trials and QC/QA.

CONCLUSION

The present communication has provided a comprehensive, systematic, and critically analyzed vision into the traditional uses, phytochemistry, and modern therapeutic applications of the genus Rauvolfia are validated by scientific evidence. In addition, different plant parts from this genus, especially raw and finished herbal products of the roots of R. serpentina have been demonstrated for the QC/QA.

Combination of HPLC-Q-TOF-MS/MS, Network Pharmacology, and Molecular Docking to Reveal the Mechanism of Apple Pollen in the Treatment of Type 2 Diabetes Mellitus

Studies have found that apple pollen can restrain the activity of amylase. Therefore, we speculate that it may be prescribed to treat patients with type 2 diabetes mellitus (T2DM), while its chemical and pharmacologic profiles remain to be further explained. In this study, the potential bioactive compounds of apple pollen and the underlying mechanism of action were investigated by performing chemical and network pharmacology analysis. Therefore, HPLC-QTOF-MS/MS analysis based on chemical compound libraries was applied in identifying the chemical profiles of apple pollen and network pharmacology was adopted for predicting the potential targets of the active components of apple pollen. Initially, the chemical map of apple pollen was identified and characterized. Secondly, the potential targets of active compounds of apple pollen were predicted with the Swiss Target Prediction and PharmMapper databases, whereas targets of T2DM were collected from the GeneCards and OMIM database. Thereafter, the target of active compounds and T2DM targets established common targets using Venn. Afterwards, the common targets were imported into the STRING database in order to construct the protein-protein interaction (PPI) network and select the core targets of apple pollen treatment of T2DM. In addition, GO and KEGG signaling pathway enrichment analyses were conducted on the selected core targets using the DAVID database. As a result, totally 28 compounds were identified. Meanwhile, network pharmacological analysis showed that 3-hydroxy-3-methyl glutaric acid, 5-hydroxyindoleacetic acid, DL-3-phenyllactic acid, isorhamnetin-3-glucoside-4′-glucoside, isorhamnetin-3-O-glucoside, syringetin-3-O-galactoside, rhamnetin, m-coumaric acid, quercitrin, isorhamnetin-3-galactoside-6″-rhamnoside, and kaempferol-3-O-alpha-L-arabinoside might be the active compounds of apple pollen. Moreover, AKT1, PPARG, SRC, EGFR, CASP3, ESR1, and the other potential core targets might be involved in the treatment of T2DM by modulating the following pathways, containing insulin resistance, hepatitis C, pancreatic cancer, insulin signaling pathway, TNF signaling pathway, and PI3K-AKT signaling pathway. Quercitrin, kaempferol, and isorhamnetin-3-O-glucoside bound most stably to AKT1. Isorhamnetin-3-O-glucoside and quercitrin bound most stably to SRC. In addition, arachidonic acid bound most stably to PPARG.

Medicinal Plants for Anti-neurodegenerative diseases in West Africa

ETHNOPHARMACOLOGICAL RELEVANCE

Neurodegenerative diseases are neuronal diseases that affect the brain components by degenerating the structure and function of the central or peripheral nervous system progressively. It is a leading cause of death and affects huge amount of people worldwide. Plant-based medicines have been utilised in the therapies for many illnesses that have defied western treatments, including neurodegenerative diseases.

AIM OF THIS REVIEW

This review presents an overview of the major neurodegenerative diseases and reported prominent medicinal plants used in managing those diseases in West Africa.

METHODS

Scientific articles regarding medicinal plants and their usefulness in managing neurodegenerative diseases in West Africa were pooled from different scientific databases. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses to filter articles based on their relevance. Pharmacological activity, plant parts used, experimental models, and some isolated chemical compounds of those plants were summarised.

RESULTS

In the West Africa region, Fabaceae (19%) and Solanaceae (13%) have the highest representation of plant families used to treat neurological diseases, while Apocynaceae, Asteraceae, Euphorbiaceae have also been utilised. Flavonoids, alkaloids, phenolic compounds, terpenoids, coumarins present in those plants and their derivatives are reported to possess neuro-protective effects. Biochemical enzymes correlating to antioxidants, anti-inflammatory effects are the potential targets against neurodegenerative diseases.

CONCLUSION

Medicinal plants for anti-neurodegenerative diseases in West Africa have been documented with their neuropharmacological activities. Plant families such as Fabaceae, Solanaceae, Apocynaceae, Asteraceae, and Euphorbiaceae could be a major natural source for discovery of anti-neurodegenerative drugs, thus the metabolites from them should be given priority for neurological research. This review will provide clues for further investigations on the screening and development of anti-neurodegenerative natural products from West African medicinal plants.

Catharanthus roseus (L.) G. Don: A review of its ethnobotany, phytochemistry, ethnopharmacology and toxicities

ETHNOPHARMACOLOGICAL RELEVANCE

Catharanthus roseus (L.) G. Don is a well known medicinal plant belonging to family Apocynaceae that have been traditionally used as medicine since ancient times. C. roseus is a well-recognized herbal medicine due to its anticancer bisindole alkaloids (vinblastine (111), vincristine (112) and vindesine (121)). In the Ayurvedic system of medicine, different parts of C. roseus are used in folklore herbal medicine for treatment of many types of cancer, diabetes, stomach disorders, kidney, liver and cardiovascular diseases.

AIM OF THE STUDY

The main idea behind this communication is to update comprehensively and analyze critically the traditional applications, phytochemistry, pharmacological activities, and toxicity of various extracts and isolated compounds from C. roseus.

MATERIALS AND METHODS

The presented data covers scientific works on C. roseus published across the world between 1967 and 2021 was searched from various international publishing houses using search engines as well as several traditional texts like Ayurveda and relevant books. Collected data from different sources was comprehensively summarized/analyzed for ethnomedicinal uses, phytochemistry, analytical chemistry, biological activities and toxicity studies of C. roseus.

RESULTS AND DISCUSSION

C. roseus has a wide range of applications in the traditional system of medicine especially in cancer and diabetes. During phytochemical investigation, total of 344 compounds including monoterpene indole alkaloids (MIAs) (110), bisindole alkaloids (35), flavonoids (34), phenolic acids (9) and volatile constituents (156) have been reported in the various extracts and fractions of different plant parts of C. roseus. The extracts and isolated compounds of C. roseus have to exhibit many pharmacological activities such as anticancer/cytotoxic, antidiabetic, antimicrobial, antioxidant, larvicidal and pupicidal. The comparative toxicity of extracts and bioactive compounds investigated in dose dependent manner. The investigation of toxicity showed that the both extracts and isolated compounds are safe to a certain limit beyond that they cause adverse effects.

CONCLUSION

This review is a comprehensive, critically analyzed summarization of sufficient baseline information of selected topics in one place undertaken till date on C. roseus for future works and drug discovery. The phytochemical investigation including biosynthetic pathways showed that the MIAs and bisindole alkaloids are major and characteristic class of compounds in this plant. The present data confirm that the extracts/fractions and their isolated alkaloids especially vinblastine (111) and vincristine (112) have a potent anticancer/cytotoxic and antidiabetic property and there is a need for further study with particular attention to the mechanisms of anticancer activity. In biosynthesis pathways of alkaloids especially bisindole alkaloids, some enzymes and rearrangement are unexposed therefore it is required to draw special attention. It also focuses on attracting the attention of scientific communities about the widespread biological activities of this species for its better utilization prospects in the near future.

Strictosidine synthase, an indispensable enzyme involved in the biosynthesis of terpenoid indole and β-carboline alkaloids

Terpenoid indole (TIAs) and β-carboline alkaloids (BCAs), such as suppressant reserpine, vasodilatory yohimbine, and antimalarial quinine, are natural compounds derived from strictosidine. These compounds can exert powerful pharmacological effects but be obtained from limited source in nature. the whole biosynthetic pathway of TIAs and BCAs, The Pictet-Spengler reaction catalyzed by strictosidine synthase (STR; EC: 4.3.3.2) is the rate-limiting step. Therefore, it is necessary to investigate their biosynthesis pathways, especially the role of STR, and related findings will support the biosynthetic generation of natural and unnatural compounds. This review summarizes the latest studies concerning the function of STR in TIA and BCA biosynthesis, and illustrates the compounds derived from strictosidine. The substrate specificity of STR based on its structure is also summarized. Proteins that contain six-bladed four-stranded β-propeller folds in many organisms, other than plants, are listed. The presence of these folds may lead to similar functions among organisms. The expression of STR gene can greatly influence the production of many compounds. STR is mainly applied to product various valuable drugs in plant cell suspension culture and biosynthesis in other carriers.

Antimicrobial and cytotoxic activities of indole alkaloids and other constituents from the stem barks of Rauvolfia caffra Sond (Apocynaceae)

Twenty indole alkaloids, among which two undescribed ones named rauvolfianoids A (1) and B (2), were isolated from the stem barks of Rauvolfia caffra Sond along with eight other compounds from other biosynthetic pathways. The structures were elucidated by analysis of spectroscopic data, including 1 D and 2 D NMR; absolute configurations of 1 and 2 were determined by CD exciton chirality method. Compounds 1 and 2 were evaluated for antimicrobial and anticancer activities against three bacterial strains (Escherichia coli, Shigella sp and Salmonella sp) and CRC-related opportunistic pathogens. 1 showed moderate antibacterial activity against Salmonella sp with the MIC value of 25 μg/ml, while 2 exhibited weak selective activity against all tested pathogens. In addition, these alkaloids were characterized as weak apoptosis inducers in HCT116 human colon carcinoma cell line.

Simultaneous determination of five alkaloids from Rauvolfia vomitoria in rat plasma by LC-MS/MS: Application to a comparative pharmacokinetic study in normal and type 2 diabetic rats

Rauvolfia vomitoria is widely distributed in the tropical regions of Africa and Asia, and has been used in traditional folk medicine in China. Indole alkaloids were found to be major bioactive components, while the effects of diabetes mellitus on the pharmacokinetic parameters of the components have not been reflected in vivo. In this study, an efficient and sensitive liquid chromatography-tandem mass spectrometry method was developed and validated for the simultaneous determination of five ingredients of R. vomitoria in rats. Detection was implemented in multiple-reaction-monitoring mode with an electrospray positive-ionization source. Validation parameters were all in accordance with the current criterion. The established method was effectively employed to compare the pharmacokinetic behaviors of five alkaloids (reserpine, yohimbine, ajmaline, ajmalicine, and serpentine) between normal and type 2 diabetic rats. The single-dose pharmacokinetic parameters of the five alkaloids were determined in normal and diabetic rats after oral administration of 100 and 200 mg/kg body weight. The results indicated that diabetes mellitus significantly altered the pharmacokinetic characteristics of yohimbine, ajmaline, and ajmalicine after oral administration in rats. This is an attempt to provide some evidence for clinicians that may serve as a guide for the use of antidiabetic medicine in clinical practice.

J, Unnithan JK, K.M. P, Balachandran I. Identification of suitable substitute for Sarpagandha (Rauvolfia serpentina (L.) Benth. ex Kurz) by phytochemical and pharmacological evaluation

Background

Sarpagandha is an important Ayurveda drug used for treating many diseases including high blood pressure. Rauvolfia serpentina is the genuine source plant for Sarpagandha and it is a critically endangered species belonging to the family Apocynaceae. The present study is aimed at finding out an appropriate substitute for the endangered species R. serpentina by evaluating the phytochemistry and biological activities of allied species such as Rauvolfia tetraphylla L, Rauvolfia hookeri S.R.Sriniv. & Chithra, Rauvolfia micrantha Hook.f., and Rauvolfia verticillata (Lour.) Baill.

Results

The result indicated that the root of R. serpentina is phytochemically similar with that of R. tetraphylla. Chemical profiling using HPTLC showed similar chemical profiles for R. serpentina and R. tetraphylla. LC/MS characterization of various species showed that most of the active alkaloids are common for both R. serpentina and R. tetraphylla. Anti-hypertensive activity and analgesic activity were evaluated in experimental animal model. Rauvolfia serpentina and R. tetraphylla showed comparatively significant reduction in systolic and diastolic pressure. Comparable analgesic activity was also shown by R. serpentina and R. tetraphylla.

Conclusion

On the basis of phytochemical and pharmacological evaluation, it was concluded that the root of R. tetraphylla can be used as a validated substitute for Sarpagandha.

Graphical abstract

A Fast and Reliable UHPLC-MS/MS-Based Method for Screening Selected Pharmacologically Significant Natural Plant Indole Alkaloids

Many substances of secondary plant metabolism have often attracted the attention of scientists and the public because they have certain beneficial effects on human health, although the reason for their biosynthesis in the plant remains unclear. This is also the case for alkaloids. More than 200 years have passed since the discovery of the first alkaloid (morphine), and several thousand substances of this character have been isolated since then. Most often, alkaloid-rich plants are part of folk medicine with centuries-old traditions. What is particularly important to monitor for these herbal products is the spectrum and concentrations of the present active substances, which decide whether the product has a beneficial or toxic effect on human health. In this work, we present a fast, reliable, and robust method for the extraction, preconcentration, and determination of four selected alkaloids with an indole skeleton, i.e., harmine, harmaline, yohimbine, and ajmalicine, by ultra-high performance liquid chromatography coupled with tandem mass spectrometry. The applicability of the method was demonstrated for tobacco and Tribulus terrestris plant tissue, the seeds of Peganum harmala, and extract from the bark of the African tree Pausinystalia johimbe.

Medicinal chemistry of indole derivatives: Current to future therapeutic prospectives

Indole is a versatile pharmacophore, a privileged scaffold and an outstanding heterocyclic compound with wide ranges of pharmacological activities due to different mechanisms of action. It is an superlative moiety in drug discovery with the sole property of resembling different structures of the protein. Plenty of research has been taking place in recent years to synthesize and explore the various therapeutic prospectives of this moiety. This review summarizes some of the recent effective chemical synthesis (2014-2018) for indole ring. This review also emphasized on the structure-activity relationship (SAR) to reveal the active pharmacophores of various indole analogues accountable for anticancer, anticonvulsant, antimicrobial, antitubercular, antimalarial, antiviral, antidiabetic and other miscellaneous activities which have been investigated in the last five years. The precise features with motives and framework of each research topic is introduced for helping the medicinal chemists to understand the perspective of the context in a better way. This review will definitely offer the platform for researchers to strategically design diverse novel indole derivatives having different promising pharmacological activities with reduced toxicity and side effects.

Simultaneous determination of intestinal permeability and potential drug interactions of complex mixtures using Caco-2 cells and high-resolution mass spectrometry: Studies with Rauwolfia serpentina extract

Caco-2 cells are a commonly used model for estimating the intestinal bioavailability of single chemical entity pharmaceuticals. Caco-2 cells, when induced with calcitriol, also express other biological functions such as phase I (CYP) and phase II (glucuronosyltransferases) drug metabolizing enzymes which are relevant to drug-supplement interactions. Intestinal bioavailability is an important factor in the overall safety assessment of products consumed orally. Foods, including herbal dietary supplements, are complex substances with multiple chemical components. Because of potential interactions between components of complex mixtures, more reliable safety assessments can be obtained by studying the commercial products "as consumed" rather than by testing individual chemical components one at a time. The present study evaluated the apparent intestinal permeability (P_app) of a model herbal extract, Rauwolfia serpentina, using both whole plant extracts and the individual purified Rauwolfia alkaloids. All test compounds, endpoint substrates, and their metabolites were quantified using liquid chromatography and high-resolution mass spectrometry. The P_app values for individual Rauwolfia alkaloids were comparable whether measured individually or as components of the complete extract. Both Rauwolfia extract and all individual Rauwolfia alkaloids except yohimbine inhibited CYP3A4 activity (midazolam 1'-hydroxylation). Both Rauwolfia extract and all individual Rauwolfia alkaloids except corynanthine and reserpic acid significantly increased glucuronosyltransferase activity (glucuronidation of 4-methylumbelliferone). The positive control, ketoconazole, significantly inhibited both CYP3A4 and glucuronosyltransferase activities. These findings suggest that the Caco-2 assay is capable of simultaneously identifying both bioavailability and potentially hazardous intestinal drug-supplement interactions in complex mixtures.

Extraction, fractionation and re-fractionation of Artemisia nilagirica for anticancer activity and HPLC-ESI-QTOF-MS/MS determination

ETHNOPHARMACOLOGICAL RELEVANCE

Medicinal plants used in traditional medicines are affordable, easily accessible, safer, less toxic and considered as a rich or efficient source of bioactive molecules for modern therapeutics. Artemisia nilagirica (AR) has a long history of use in Indian traditional medicine to combat a wide variety of diseases including cancer.

AIM OF THE STUDY

Considering the vast potential of traditional healing plants to deliver safer, less toxic and efficient chemotherapeutics, we have examined anticancer activity of ethanolic extract, bioactive fractions and sub-fractions of AR against different human cancer cell lines along with their phytochemical analysis to understand the insights of novel anticancer activities for further preclinical studies.

MATERIALS AND METHODS

Fresh plant material of AR was procured from the wild, dried and ground. The grinded materials was extracted in ethanol (AR-01) and fractionated into butanol (AR-02), ethyl acetate (AR-03), hexane (AR-04) and water (AR-05). The cytotoxicity was evaluated against three different human cancer cell lines, i.e. colon (DLD-1), lung (A-549), and breast (MCF-7) using Sulforhodamine B (SRB) assay along with non-cancerous VERO cells as control and doxorubicin (DOX) as positive control. As we observed strong cytotoxicity of AR-03 and AR-04 fractions against tested cells and marked cytotoxic effects particularly in colon cancer cell lines, we further re-fractionated, AR-03 into (AR-03A, AR-03B, AR-03C, AR-03D, AR-03E) and AR-04 into (AR-04A, AR-04B, AR-04C) sub-fractions by column chromatography and investigated against the same panel of cell lines in addition to one more colon cancer cell line (HT-29). Phytochemical analysis was performed through HPLC-ESI-QTOF-MS/MS fragmentation.

RESULTS

Ethyl acetate (AR-03) and hexane (AR-04) fractions were found to be the most cytotoxic against all the tested cell lines. Further, AR-03E and AR-04A sub-fractions were found more specific cytotoxic selectively against DLD-1 cancer cell lines at 100µg/ml concentration. HPLC-ESI-QTOF-MS/MS determination revealed the presence of 17 compounds in AR-01. Among them, 4 compounds were reported for the first time in this species. However, 3 identified compounds (artemorin, β-santonin and caryophyllene oxide) in AR-03E sub-fraction were commonly present in each bioactive fraction and may be considered as potential and safest cytotoxic agents for anticancer activity.

CONCLUSIONS

Experimental evidences reported in this paper for anticancer activity validate the traditional wisdom of Artemisia nilagirica as an anticancer herbal drug. To our knowledge, this is our first novel observation of cytotoxicity and selectivity of ethyl acetate and hexane sub-fraction of AR-01 i.e. AR-03E and AR-04A respectively against DLD-1 human cancer cell lines. HPLC-ESI-QTOF-MS/MS determination attributes the identification of cytotoxic compounds which may be used for further preclinical studies.

Identification, characterization and distribution of terpene indole alkaloids in ethanolic extracts of Catharanthus roseus using high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry and the study of their geographical variation

RATIONALE

Catharanthus roseus is a well-known dicotyledonous medicinal plant containing diverse classes of bioactive terpene indole alkaloids (TIAs), in particular the anticancer agents vinblastine and vincristine. In view of the commercial importance of these compounds there is an urgent need to develop an accurate and reliable method for the screening of TIAs from C. roseus.

METHODS

A method for the separation and characterization of these compounds was developed using high-performance liquid chromatography coupled with positive electrospray ionization quadrupole time-of-flight tandem mass spectrometry (HPLC/ESI-QTOF-MS/MS). Chromatographic separation of TIAs was carried out using a Thermo Betasil C8 column (250 mm × 4.5 mm, 5 μm) at 25°C using 0.1% formic acid in water and acetonitrile.

RESULTS

Diagnostic fragmentation pathways for vinpocetine, vindesine, catharanthine, vinblastine, vindoline and vincristine were established on the basis of their product ions. A total of 72 TIAs were detected of which 11 were unambiguously identified by comparison with their standards, and the remaining 61 were tentatively identified. The geographical distribution of the TIAs in ethanolic extracts of 30 samples of C. roseus collected from five states of India was studied using principal component analysis (PCA).

CONCLUSIONS

The developed analytical method together with diagnostic fragment patterns were used to rapidly and effectively identify targeted and untargeted TIAs in C. roseus. A PCA study of the results obtained was used to discriminate among the C. roseus samples.

Identification and characterization of phenolics and terpenoids from ethanolic extracts of Phyllanthus species by HPLC-ESI-QTOF-MS/MS

Phyllanthus species plants are a rich source of phenolics and widely used due to their medicinal properties. A liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed using high-pressure liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (HPLC-ESI-QTOF-MS/MS) for the identification and characterization of quercetin, kaempferol, ellagic acid and their derivatives in ethanolic extracts of Phyllanthus species. The chromatographic separation was carried out on Thermo Betasil C₈ column (250 mm×4.5 mm, 5 µm) using 0.1% formic acid in water and 0.1% formic acid in methanol as the mobile phase. The identification of diagnostic fragment ions and optimization of collision energies were carried out using 21 reference standards. Totally 51 compounds were identified which include 21 compounds identified and characterized unambiguously by comparison with their authentic standards and the remaining 30 were tentatively identified and characterized in ethanolic extracts of P. emblica, P. fraternus, P. amarus and P. niruri.

Simultaneous Determination of Bioactive Monoterpene Indole Alkaloids in Ethanolic Extract of Seven Rauvolfia Species using UHPLC with Hybrid Triple Quadrupole Linear Ion Trap Mass Spectrometry

INTRODUCTION

Rauvolfia serpentina is an endangered plant species due to its over-exploitation. It has highly commercial and economic importance due to the presence of bioactive monoterpene indole alkaloids (MIAs) such as ajmaline, yohimbine, ajmalicine, serpentine and reserpine.

OBJECTIVE

To develop a validated, rapid, sensitive and selective ultra-high-performance liquid chromatography coupled with hybrid triple quadrupole-linear ion trap mass spectrometry (UHPLC-QqQLIT -MS/MS) method in the multiple reaction monitoring (MRM) mode for simultaneous determination of bioactive MIAs in ethanolic extract of seven Rauvolfia species and herbal formulations.

METHODS

The separation of MIAs was achieved on an ACQUITY UPLC BEH™ C18 column (1.7 μm, 2.1 mm × 50 mm) using a gradient mobile phase (0.1% aqueous formic acid and acetonitrile) at flow rate 0.3 μL/min in 7 min. The validated method showed good linearity (r(2)  ≥ 0.9999), limit of detection (LOD) (0.06-0.15 ng/mL), limit of quantitation (LOQ) (0.18-0.44 ng/mL), precisions [intraday: relative standard deviation (RSD) ≤ 2.24%, interday: RSD ≤ 2.74%], stability (RSD ≤ 1.53%) and overall recovery (RSD ≤ 2.23%).

RESULTS

The validated method was applied to quantitate MIAs. Root of Rauvolfia vomitoria showed a high content of ajmaline (48.43 mg/g), serpentine (87.77 mg/g) whereas high quantities of yohimbine (100.21 mg/g) and ajmalicine (120.51 mg/g) were detected in R. tetraphylla. High content of reserpine was detected in R. micrantha (35.18 mg/g) and R. serpentina (32.38 mg/g).

CONCLUSION

The encouraging results of this study may lead to easy selection of suitable Rauvolfia species according to the abundance of MIAs. Copyright © 2016 John Wiley & Sons, Ltd.