Phytochemicals with NO inhibitory effects and interactions with iNOS protein from Trigonostemon howii

Sustainable biosynthesis of valuable diterpenes in microbes

Diterpenes, or diterpenoids, are the most abundant and diverse subgroup of terpenoids, the largest family of secondary metabolites. Most diterpenes possess broad biological activities including anti-inflammatory, antiviral, anti-tumoral, antimicrobial, anticancer, antifungal, antidiabetic, cardiovascular protective, and phytohormone activities. As such, diterpenes have wide applications in medicine (e.g., the anticancer drug Taxol and the antibiotic pleuromutilin), agriculture (especially as phytohormones such as gibberellins), personal care (e.g., the fragrance sclareol) and food (e.g., steviol glucosides as low-calorie sweeteners) industries. Diterpenes are biosynthesized in a common route with various diterpene synthases and decoration enzymes like cytochrome P450 oxidases, glycosidases, and acyltransferases. Recent advances in DNA sequencing and synthesis, omics analysis, synthetic biology, and metabolic engineering have enabled efficient production of diterpenes in several chassis hosts like Escherichia coli, Saccharomyces cerevisiae, Yarrowia lipolytica, Rhodosporidium toruloides, and Fusarium fujikuroi. This review summarizes the recently discovered diterpenes, their related enzymes and biosynthetic pathways, particularly highlighting the microbial synthesis of high-value diterpenes directly from inexpensive carbon sources (e.g., sugars). The high titers (>4 g/L) achieved mean that some of these endeavors are reaching or close to commercialization. As such, we envisage a bright future in translating microbial synthesis of diterpenes into commercialization.

Trigonostemon species in south China: Insights on its chemical constituents towards pharmacological applications

ETHNOPHARMACOLOGY RELEVANCE

The Euphorbiaceae family, which contains about 300 genera and more than 5000 species, is widely distributed in different regions. Trigonostemon genus comprises a wide group of tropical and temperate plants belonging to the Euphorbiaceae family. This genus includes at least 50 species throughout tropical Asia, extending from India and Sri Lanka to New Guinea. They have been employed by local populations for the treatment of asthma, poisonous snake bites, and food poisoning.

AIM OF THE REVIEW

The main aim of the review is to critically analyze the reported traditional uses, bioactive chemical constituents and pharmacological activities of Trigonostemon species.

MATERIALS AND METHODS

Scientific databases, including Google Scholar, PubMed, CNKI, SpringerLink, Web of Science, Wiley Online Library and SciFinder, were searched using keywords such as "Trigonostemon", "South China", "chemical constituents", or "traditional use". Thus, available articles from 2000 to 2020 were collected and analyzed.

RESULTS AND DISCUSSION

This paper provides systematic data that Trigonostemon species possess a diverse phytochemical composition, (including diterpenes, alkaloids, coumarins, lignins, sesquiterpenes, triterpenoids, flavonoids, and polyphenols) found in different plant organs. Research on Trigonostemon plants has revealed critical therapeutic properties, such as antiviral, anti-tumor, antimicrobial, anti-inflammatory, and insecticidal activities.

CONCLUSIONS

It is envisaged that the current review will add value to more scientific research on Trigonostemon species and enhance/promote the increased interest in the sustainable use of Trigonostemon species as well as lead to the validation of unverified ethnobotanical claims. Future studies on Trigonostemon species would focus on establishing the links between the traditional uses, active compounds and reported pharmacological activities.

New 3,4-seco-diterpene and coumarin derivative from the leaves of Trigonostemon flavidus Gagnep

Two new compounds named trigoflavidus A (1) and trigoflavidus B (2), and eight known compounds, trigoflavidone (3), heterophypene (4), howpene C (5), 3,4-seco-sonderianol (6), trigonochinene C (7), fraxidin (8), isofraxidin (9), and isofraxetin (10) were isolated from the leaves of Trigonostemon flavidus Gagnep. by various chromatographic methods. Their chemical structures were elucidated via UV, IR, HR-ESI-MS and NMR spectroscopic methods and divided into two groups including six 3,4-seco-diterpenes (1, 3-7) and four coumarins (2, 8-10). Absolute configurations at stereocenters of compound 1 were confirmed by comparison of its CD spectra with those of the TD-DFT calculations. At a concentration of 30 µM, compounds 1-10 exhibited weak cytotoxic activity toward LU1, HepG2, MCF7, and SKMel2 human cell lines (cell viability all over 50%).

Erinacine A and related cyathane diterpenoids: Molecular diversity and mechanisms underlying their neuroprotection and anticancer activities

The presence of a fused 5/6/7 tricyclic core characterizes the group of cyathane diterpene natural products, that include more than 170 compounds, isolated from fungi such as Cyathus africanus and Hericium erinaceus. These compounds have a common biosynthetic precursor (cyatha-3,12-diene) and can be produced bio- or hemi-synthetically, or via total syntheses. Cyathane diterpenes display a range of pharmacological properties, including anti-inflammatory (possibly through binding to the iNOS protein) and neuroprotective effects. Many cyathanes like cyahookerin C, cyathin Q and cyafranines B and G can stimulate neurite outgrowth in cells, whereas conversely a few molecules (such as scabronine M) inhibit NGF-stimulated neurite outgrowth. The main anticancer cyathanes are erinacine A and cyathins Q and R, with a capacity to trigger cancer cell death dependent on the production of reactive oxygen species (ROS). These compounds, active both in vitro and in vivo, activate different signaling pathways in tumor cells to induce apoptosis (and autophagy) and to upregulate the expression of several proteins implicated in the organization and functioning of the actin cytoskeleton. An analysis of the functional analogy between erinacine A and other natural products known to interfere with the actin network in a ROS-dependent manner (notably cucurbitacin B) further supports the idea that erinacine A functions as a perturbator of the cytoskeleton organization. Collectively, we provide an overview of the molecular diversity of cyathane diterpenes and the main mechanisms of action of the lead compounds, with the objective to encourage further research with these fungal products. The anticancer potential of erinacine A deserves further attention but it will be necessary to better characterize the implicated targets and signaling pathways.

NO inhibitory diterpenoids as potential anti-inflammatory agents from Euphorbia antiquorum

Two new ent-atisane-type diterpenoids (1 and 2), three new lathyrane-type diterpenoids (3-5), and seven known analogues (6-12) were isolated from Euphorbia antiquorum. The structures of these diterpenoids were established by analysis of their NMR, MS, and electronic circular dichroism data. The anti-inflammatory activities were evaluated biologically and compounds 1, 4, 7, 8, and 10 displayed strong NO inhibitory effects with IC₅₀ values less than 40 μM. The potential anti-inflammatory mechanism was also investigated using molecular docking and Western blotting.

Potential in vitro anti-allergic, anti-inflammatory and cytotoxic activities of ethanolic extract of Baliospermum montanum root, its major components and a validated HPLC method

Background

The root of Baliospermum montanum has been used as an ingredient of traditional Thai medicines for the treatments of several diseases including itching eczema, muscle and joint inflammation, and cancer. Few studies have been done on phytochemical components of this root. In this study, we isolated major compounds of the crude ethanolic extract of B. montanum root and developed and validated a high performance liquid chromatographic (HPLC) method for the determination of its major components. We then investigated anti-allergic, anti-inflammatory and cytotoxic activities of the extract.

Methods

The aims of this study were to investigate in vitro activities including inhibitory effect of β-hexosaminidase released from RBL-2H3 cells, inhibition of nitric oxide (NO) production from RAW 264.7 cells and cytotoxic activity against cancerous liver cell lines (HepG2 and KKU M156) by using sulforhodamine B (SRB) assay. Isolation of major components was conducted by using column chromatographic method. Isolated major compounds were analyzed by using high performance liquid chromatography (HPLC).

Results

The crude extract exhibited the highest cytotoxic activity, with IC₅₀ less than 1 μg/mL, while its anti-allergy and anti-inflammation were also potent with IC₅₀ less than 6 μg/mL. Three propiophenones isolated from B. montanum root exhibited moderate cytotoxic activities (IC₅₀ > 20 μg/mL). Two of the propiophenones found were major components that can be detected by HPLC. The developed and validated HPLC method showed good accuracy, precision, and linearity.

Conclusion

The results of this study suggested that ethanolic extract of of B.montanum root can be a potential source of anti-allergy, anti-inflammation, and anti-cancer compounds. The isolated compounds can serve as markers when B. montanum is used in herbal remedies but not as overall responsive markers. The HPLC method developed may be useful for quality control in the production of the extract and for further formulation developments. However, investigation of several associated biological activities is necessary before the development can proceed further. Minor active compounds should be isolated and a more sensitive analytical method should be developed to detail the key responsive components of the ethanolic extract of B. montanum root.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2449-0) contains supplementary material, which is available to authorized users.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial sources from 2017.