Secoiridoid glucosides and unusual recyclized secoiridoid aglycones from Ligustrum vulgare

Swertia chirayita: A comprehensive review on traditional uses, phytochemistry, quality assessment and pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Swertia chirayita (Roxb.) H. Karst. is a traditionally used, well-recognized medicinal plant of the family Gentianaceae with significant therapeutic potential. It has been traditionally used to cure various ailments such as fever, vomiting, jaundice, digestive disorders, heart diseases, diabetes, malaria, scorpion bite, and skin diseases.

AIM OF REVIEW

The present review emphasized the traditional uses, phytochemistry, pharmacology, toxicology, chemical profiling, and structural identification of isolated compounds by analytical and spectroscopic techniques. This review demonstrates the possibility of advanced ethnopharmacological research.

MATERIALS AND METHODS

The literature on S. chirayita was obtained from bibliographic databases like Web of Science, PubMed, Science-Direct, American Chemical Society (ACS), Google Scholar, and SciFinder. The compiled review is covered up until March 2022.

RESULTS

Approximately, 123 specialized metabolites including xanthones, seco-iridoids, terpenoids, alkaloids, and flavonoids have been isolated and characterized from S. chirayita. The extract and isolated compounds exhibited a wide spectrum of pharmacological effects such as anti-inflammatory, antioxidant, antitumor, hepatoprotective, antiviral, antimalarial, and antibacterial offering scientific evidence for traditional claims of this medicinal plant. In addition, various analytical methods using HPTLC, UPLC, HPLC, LC-MS, and GC-MS have also been documented to determine the phytochemicals of S. chirayita.

CONCLUSION

The current article provides information on traditional usage, phytochemistry, chemical profiling, structure elucidation, pharmacological efficacy, toxicity, and future prospects of S. chirayita. This plant has long been traditionally used in a variety of ways by indigenous people. Numerous phytoconstituents and several pharmacological activities have been reported in S. chirayita. However, there are still some scientific gaps such as identification of bioactive compounds, structure-activity relationship and mechanistic action of isolated bioactive compounds, development of effective analytical methods for comprehensive quality control, and safety profiles that need to be addressed.

Preliminary results on the separation of the different parts of Ligustrum lucidum Ait fruit and the main bioactive compounds analysis

Oleanolic acid (OA) and ursolic acid (UA) possess anti-inflammatory, antioxidative, antiprotozoal, antimutagenic and anticancer properties and are the main bioactive compounds in the fruit of Ligustrum lucidum Ait. The aim of this paper was to study the method of separating the whole fruit into the main ingredients containing OA and UA for the later effective extraction with reduced organic solvents and easy separation and purification. In the present study, the sarcocarps and exocarps were separated from the whole fruits (designated exo-sarcocarps, the mass percentages (w/w, dry weight basis), 33.1%), testae (13.5%) and cores (48.7%) by using methods separated. The contents of OA and UA in whole fruits, exo-sarcocarps, testae and cores were analyzed. The OA and UA extraction yields were highest in exo-sarcocarps vs. yields from whole fruits, testae or cores. The spective yields of OA and UA from exo-sarcocarps were 24.34 ± 2.09 and 7.82 ± 0.09 mg/g; these yields were about 4 times higher than OA yields and about 4 times higher than UA yields from fruit.

The Oleaceae family: A source of secoiridoids with multiple biological activities

In the quest to search and discover bioactive compounds from nature, terpenoids have emerged as one of the most interesting and researched classes of compounds. Secoiridoid, a type of the terpenoid, has also been extensively studied, especially their chemical structures and pharmacological effects. Oleaceae is a family of woody dicotyledonous plants with broad economic and medicinal values. This family contains a large number of flavonoids, monoterpenoids, iridoids, secoiridoids and phenylethyl alcohols, of which the secoiridoids have various biological activities. The purpose of this review is to summarize the phytochemical and pharmacological of the secoiridoids (glycosides, aglycones, derivatives and dimers) in the Oleaceae family from 1987 to 2018. This review will also serve as a reference for further studies.

[Diversity of Secondary Metabolites from Some Medicinal Plants and Cultivated Lichen Mycobionts]

 Studies on the structural determination, biosynthesis, and biological activities of secondary metabolites from natural sources are significant in the field of natural products chemistry. This review focuses on diverse secondary metabolites isolated from medicinal plants and cultivated mycobionts of lichens in our laboratory. Monoterpene-tetrahydroisoquinoline glycosides and alkaloids isolated from Cephaelis acuminata and Alangium lamarckii gave important information on the biosynthesis of ipecac alkaloids. A variety of glycosides linked with a secologanin unit and indole alkaloids were obtained from medicinal plants belonging to the families of Rubiaceae, Apocynaceae, and Loganiaceae. Plant species of the four genera Fraxinus, Syringa, Jasminum, and Ligustrum of the family Oleaceae were chemically investigated to provide several types of secoiridoid and iridoid glucosides. The biosynthetic pathway leading from protopine to benzophenanthridine alkaloids in suspension cell cultures of Eschscholtzia californica was elucidated. The structures and biological activities of the bisbenzylisoquinoline alkaloids of Stephania cepharantha and Nelumbo nucifera were also investigated. In addition, the mycobionts of lichens were cultivated to afford various types of metabolites that differ from the lichen substances of intact lichens but are structurally similar to fungal metabolites. The biosynthetic origins of some metabolites were also studied. These findings suggest that cultures of lichen mycobionts could be sources of new bioactive compounds and good systems for investigating secondary metabolism in lichens.

Ash leaf metabolomes reveal differences between trees tolerant and susceptible to ash dieback disease

European common ash, Fraxinus excelsior, is currently threatened by Ash dieback (ADB) caused by the fungus, Hymenoscyphus fraxineus. To detect and identify metabolites that may be products of pathways important in contributing to resistance against H. fraxineus, we performed untargeted metabolomic profiling on leaves from five high-susceptibility and five low-susceptibility F. excelsior individuals identified during Danish field trials. We describe in this study, two datasets. The first is untargeted LC-MS metabolomics raw data from ash leaves with high-susceptibility and low-susceptibility to ADB in positive and negative mode. These data allow the application of peak picking, alignment, gap-filling and retention-time correlation analyses to be performed in alternative ways. The second, a processed dataset containing abundances of aligned features across all samples enables further mining of the data. Here we illustrate the utility of this dataset which has previously been used to identify putative iridoid glycosides, well known anti-herbivory terpenoid derivatives, and show differential abundance in tolerant and susceptible ash samples.

Chemical constituents from the fruits of Ligustrum japonicum and their inhibitory effects on T cell activation

A previously undescribed nor-dammarane, 3β,20,23-trihydroxy-24,25,26,27-tetranordammarane; three previously undescribed secoiridoid glycosides, ligujaponosides A-B, and iso-oleonuzhenide; and twenty three known compounds, were isolated from the fruits of Ligustrum japonicum Thunb. Their chemical structures were elucidated by extensive spectroscopic analyses, including 1D and 2D NMR, and HRMS. The isolated compounds were screened for immunosuppressive effects on T activated cells by evaluating interleukin-2 (IL-2) production. Among them, sesamin inhibited IL-2 production in Jurkat T cells with an IC50 value of 38 ± 2 μM. In addition, sesamin inhibited the phosphorylation of extracellular signal-regulated protein kinase (ERK), a member of the mitogen-activated protein kinase (MAPK) family, in phorbol 12-myristate 13-acetate (PMA)/A23187-stimulated T cells. Therefore, sesamin was demonstrated to inhibit T cell activation via regulation of MAPK phosphorylation pathway.

New secoiridoids from the fruits of Ligustrum lucidum Ait with triglyceride accumulation inhibitory effects

Five new secoiridoids, nuzhenal C (1), 6'-O-trans-cinnamoyl iso-8-epikingisidic acid (2), ligulucidumosides A (3), B (4), and C (5), were obtained from the fruits of Ligustrum lucidum Ait. Their structures were elucidated by chemical and spectroscopic methods (UV, IR, HRESI-TOF-MS, 1D and 2D NMR). Among them, compound 3 is the first 1-OCH3 substituent secoiridoid obtained from plant kingdom. Furthermore, activity screening results showed that all of the isolates had triglyceride accumulation inhibitory effects in HepG2 cells.

Structure and cytotoxic activity of enzymatic hydrolysis products of secoiridoid glucosides, isoligustroside and isooleuropein

Hydrolysis of isoligustroside (1) and isooleuropein (2), secoiridoid glucosides, in the presence of β-glucosidase provided 2-(4-hydroxyphenyl)methyl (2R,3S,4S)-3-formyl-3,4-dihydro-4-(2-methoxy-2-oxoethyl)-2-methyl-2H-pyran-5-carboxylate (3) and 2-(3,4-dihydroxyphenyl)methyl (2R,3S,4S)-3-formyl-3,4-dihydro-4-(2-methoxy-2-oxoethyl)-2-methyl-2H-pyran-5-carboxylate (4), respectively. The structures of 3 and 4 were elucidated on the basis of extensive spectral analyses, including 2D-NMR experiments. Compounds 3 and 4 were found to be new rearrangement products of the aglycones of 1 and 2. The cytotoxic activities of 3 and 4 were evaluated using a disease-oriented panel of 39 human cancer cell lines and showed moderate cytotoxic activity for 4, while 3 exhibited weaker activity compared to that of 4.

Seasonal variations in metabolite profiling of the fruits of Ligustrum lucidum Ait

The metabolite profiling of fruits of the herb Ligustrum lucidum Ait collected during different months has been performed using ultra-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC/QTOFMS) and multivariate statistical analysis techniques. The markers such as oleuropein acid, neonuezhenide, specnuezhenide, oleuropein and ligustrosidic acid accountable for such variations were identified through the loadings plot of principal component analysis (PCA), and the tentative identification of the markers is completed by comparing the mass spectra and retention times with those of reference compounds and/or tentatively assigned by matching empirical molecular formulae and MS/MS data with those of the known compounds published. Furthermore, one of the chemical markers, such as specnuezhenide, which is water-soluble, biologically active and also the predominant compound in this crude drug, was quantified by ultra-performance liquid chromatography coupled with a tunable UV detector (UPLC-TUV). The developed UPLC method provides good linearity (r(2)=0.9991), repeatability (RSD=2.96%), intra- and inter-day precisions (RSD=0.21%, 0.96%), with accuracies of 99.18-100.26% and a recovery of specnuezhenide of 97.57%. The fruits of L. lucidum Ait collected from August to December were tested. The results clearly show that the fruits of L. lucidum Ait harvested in October have the highest yields of specnuezhenide. It is also noted that the variations of content of specnuezhenide obtained by both methods have a strong correlation. This suggests that the newly proposed strategy is a reliable and simple method for the rapid discrimination of subtle variations, within the same plant species or strains, due to different seasonal collection times.