NO inhibitory phytochemicals as potential anti-inflammatory agents from the twigs of Trigonostemon heterophyllus

Four new diterpenoids from the aerial parts of Leucas zeylanica (L.) R. Br

Four new undescribed halimane- and labdane-type diterpenoids, named zeylleucapenoids E-H (1-4), along with four known analogues (5-8), were isolated from the aerial parts of Leucas zeylanica (L.) R. Br. Their structures were determined by comprehensive spectroscopic analysis and computational calculations. Compounds 1 and 2 are the highly modified halimane diterpenoids featuring a 6/6/6-fused tricyclic system with an unusual six-membered 6,11-ether ring. Compound 8 exhibits nontoxic effects for zebrafish embryo, while it displays efficient reduction against NO production in a dose-dependent manner and strongly suppresses the secretion of LPS-induced TNF-α and IL-6 cytokines in RAW264.7 macrophages. In addition, marked reductions of iNOS and COX-2 expression were observed. Molecular docking analysis indicated that 8 has high affinities with the target amino acid residues on protein-binding sites, which may be a possible mechanism contributing to the anti-inflammatory potential of this molecule.

Zeylleucapenoids A-D, Highly Oxygenated Diterpenoids with Anti-Inflammatory Activity from Leucas zeylanica (L.) R. Br

Four previously undescribed highly oxygenated diterpenoids (1-4), zeylleucapenoids A-D, characterized by halimane and labdane skeletons, were isolated from the aerial parts of Leucas zeylanica. Their structures were elucidated primarily via NMR experiments. The absolute configuration of 1 was established using theoretical ECD calculations and X-ray crystallographic analysis, whereas those for 2-4 were assigned using theoretical ORD calculations. Zeylleucapenoids A-D were tested for anti-inflammatory activity against nitric oxide (NO) production in RAW264.7 macrophages, of which only 4 showed significant efficacy with an IC₅₀ value of 38.45 μM. Further, active compound 4 was also evaluated for the inhibition of the release of pro-inflammatory cytokines TNF-α and IL-6 and was found to have a dose-dependent inhibitory effect, while it showed nontoxic activity for zebrafish embryos. A subsequent Western blotting experiment revealed that 4 inhibited the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, molecular docking analysis indicated that the possible mechanism of action for 4 may be bind to targets via hydrogen and hydrophobic bond interactions.

Strophiofimbrins A and B: Two Rearranged Norditerpenoids with Novel Tricyclic Carbon Skeletons from Strophioblachia fimbricalyx

Two rearranged norditerpenoids with novel tricyclic carbon skeletons, strophiofimbrin A (1) and strophiofimbrin B (2), were isolated from Strophioblachia fimbricalyx. Their structures were established by 1D/2D NMR spectroscopy, HRESIMS, quantum chemistry calculations, and X-ray diffraction analyses. 1 and 2 represented the first examples of diterpenoids with unprecedented 5/6/7-fused ring systems. In the proposed biosynthetic pathway, they were suspected to derive from cleistanthane norditerpenoids via ring opening, expansion, cyclization, and rearrangement based on the existence of phenanthrenone and cleistanthane diterpenoids from Strophioblachia and Trigonostemon, two closely related genera of the Euphorbiaceae family. Furthermore, compounds 1 and 2 exhibited significant proliferation inhibition and obvious neuroprotective effects.

Potential inhibitors of microglial activation from the roots of Vernicia montana Lour

During our continuous investigation of natural, herbal inhibitors of microglial over-activation in the Euphorbiaceae family, two plants of the Vernicia genus showed remarkable inhibitory effects on nitric oxide (NO) production in over-activated microglia. In this study, bioactivity-guided phytochemical research on the active fraction of the roots of V. montana was carried out. As a result, seven undescribed terpenoids and lignans, together with thirty-one known components, were isolated and identified using comprehensive spectral analysis. All the identified compounds were evaluated for their inhibitory effects on NO production in lipopolysaccharide-stimulated BV-2 cells. Combined with our previous research on the Vernicia genus, the effective material basis of different plants and medicinal components was analyzed systematically.

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.

3, 4-seco-Isopimarane and 3, 4-seco-pimarane diterpenoids from Callicarpa nudiflora

A phytochemical investigation was carried out on the extract of a medicinal plant Callicarpa nudiflora, resulting in the characterization of five new 3, 4-seco-isopimarane (1-5) and one new 3, 4-seco-pimarane diterpenoid (6), together with four known compounds. The structures of the new compounds were fully elucidated by extensive analysis of MS, 1D and 2D NMR spectroscopic data, and time-dependent density functional theory (TDDFT) calculation of electronic circular dichroism (ECD) spectra, and DFT calculations for NMR chemical shifts and optical rotations.

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%).

Natural iridoids from Patrinia heterophylla showing anti-inflammatory activities in vitro and in vivo

Inflammation, especially chronic inflammation, has been found to be closely related to the pathology of many diseases and the discovery of bioactive natural products to inhibit NO production is one of strategies to treat inflammation. In our continuous search for bioactive natural substances as potential anti-inflammatory agents, five new compounds (1-5) were extracted and purified from Patrinia heterophylla. The NMR and MS data analysis, along with electronic circular dichroism (ECD) calculations, led to the identification of these isolates, which were new iridoids. Using cell and zebrafish models, the in vitro and in vivo anti-inflammatory effects were conducted to evaluate the potency of anti-inflammation of these compounds. The preliminary mechanism was explored using molecular docking and Western blotting experiments.