Bioactive sesquiterpene polyol esters from the leaves of Tripterygium wilfordii

Activity of extracts and terpenoids from Tontelea micrantha (Mart. ex Schult.) A.C.Sm. (Celastraceae) against pathogenic bacteria

The pharmacological properties of plant extracts and phytochemicals, such as flavonoids and terpenoids, remain of great interest. In this work, the effect of extracts, friedelan-3,21-dione, and 3β-O-D-glucosyl-sitosterol isolated from Tontelea micrantha roots was evaluated against Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumoniae, Klebsiella oxytoca and Escherichia coli. The antibacterial activity was evaluated by the minimum inhibitory and bactericidal concentrations (MIC and MBC, respectively), and the synergistic effect was assessed by the Checkerboard assay. Furthermore, the cytotoxicity of the plant-derived compounds against Vero cells was measured by the 3-(4 5-dimethylthiazol-2-yl)-2 5-diphenyltetrazolium bromide (MTT) method. The biological effects of the isolated compounds were predicted using the PASS online software. The chloroform and hexane extracts of T. micrantha roots showed promising antibacterial effect, with MIC in the range of 4.8-78.0 µg/mL. Further analyses showed that these compounds do not affect the integrity of the membrane. The combination with streptomycin strongly reduced the MIC of this antibiotic and extracts. The extracts were highly toxic to Vero cells, and no cytotoxicity was detected for the two terpenoids isolated from them (i.e. friedelan-3,21-dione and 3β-O-D-glucosyl-sitosterol; CC50 > 1000 μg/mL). Therefore, extracts obtained from T. micrantha roots significantly inhibited bacterial growth and are considered promising agents against pathogenic bacteria. The cytotoxicity results were very relevant and can be tested in bioassays.

Anti-inflammatory sesquiterpene polyol esters from the stem and branch of Tripterygium wilfordii

The stem and branch extract of Tripterygium wilfordii (Celastraceae) afforded seven new dihydroagarofuran sesquiterpene polyesters [tripterysines A-G (1-7)] and eight known ones (8-15). The chemical structures of these new compounds were established based on combinational analysis of HR-ESI-MS and NMR techniques. The absolute configurations of tripterysines A-C (1-3) and E-G (5-7) were determined by X-ray crystallographic analysis and circular dichroism spectra. All the compounds were screened for their inhibitory effect on inflammation through determining their inhibitory effect on nitric oxide production in LPS-induced RAW 264.7 cells and the secretion of inflammatory cytokines TNF-α and IL-6 in LPS-induced BV2 macrophages. Compound 9 exhibited significant inhibitory activity on NO production with an IC₅₀ value of 8.77 μmol·L^-1. Moreover, compound 7 showed the strongest inhibitory effect with the secretion of IL-6 at 27.36%.

The Exploration of Novel Pharmacophore Characteristics and Multidirectional Elucidation of Structure-Activity Relationship and Mechanism of Sesquiterpene Pyridine Alkaloids from Tripterygium Based on Computational Approaches

Sesquiterpene pyridine alkaloids are a large group of highly oxygenated sesquiterpenoids, which are characterized by a macrocyclic dilactone skeleton containing 2-(carboxyalkyl) nicotinic acid and dihydro-β-agarofuran sesquiterpenoid, and are believed to be the active and less toxic components of Tripterygium. In this study, 55 sesquiterpene pyridine alkaloids from Tripterygium were subjected to identification of pharmacophore characteristics and potential targets analysis. Our results revealed that the greatest structural difference of these compounds was in the pyridine ring and the pharmacophore model-5 (Pm-05) was the best model that consisted of three features including hydrogen bond acceptor (HBA), hydrogen bond donor (HBD), and hydrophobic (HY), especially hydrophobic group located in the pyridine ring. It was proposed that 2-(carboxyalkyl) nicotinic acid part possessing a pyridine ring system was not only a pharmacologically active center but also a core of structural diversity of alkaloids from Tripterygium wilfordii. Furthermore, sesquiterpene pyridine alkaloids from Tripterygium were predicted to target multiple proteins and pathways and possibly played essential roles in the cure of Alzheimer's disease, breast cancer, Chagas disease, and nonalcoholic fatty liver disease (NAFLD). They also had other pharmacological effects, depending on the binding interactions between pyridine rings of these compounds and active cavities of the target genes platelet-activating factor receptor (PTAFR), cannabinoid receptor 1 (CNR1), cannabinoid receptor 1 (CNR2), squalene synthase (FDFT1), and heat shock protein HSP 90-alpha (HSP90AA1). Taken together, the results of this present study indicated that sesquiterpene pyridine alkaloids from Tripterygium are promising candidates that exhibit potential for development as medicine sources and need to be promoted.

Natural Nitrogenous Sesquiterpenoids and Their Bioactivity: A Review

Nitrogenous sesquiterpenoids fromnatural sourcesare rare, so unsurprisingly neither the potentially valuable bioactivity nor thebroad structural diversity of nitrogenous sesquiterpenoids has been reviewed before. This report covers the progressduring the decade from 2010 to February 2020 on the isolation, identification, and bioactivity of 391 nitrogen-containing natural sesquiterpenes from terrestrial plant, marine organisms, and microorganisms. This complete and in-depth reviewshouldbe helpful for discovering and developing new drugs of medicinal valuerelated to natural nitrogenous sesquiterpenoids.

Dihydroagarofuran sesquiterpenoids esterified with organic acids from the leaves of Tripterygium wilfordii

Six new and one known dihydroagarofuran sesquiterpenoids esterified with organic acids were obtained from the leaves of Tripterygium wilfordii. Spectroscopic techniques (UV, IR, MS, NMR, ORD and CD) were used for the structure elucidation of the compounds. The structures of compounds 1 and 2 were confirmed by X-ray single crystallographic analyses. The inhibitory effects on NO production in LPS-induced macrophages of 1-7 were conducted. At 10 μmol/L, compounds 1, 2 and 7 showed moderate inhibitory effects on NO production in LPS-induced macrophages with inhibitory rate at 31.2 ± 3.6, 40.9 ± 4.3, and 66.79 ± 3.1%, respectively.

New 18(4→3)-Abeo-Abietanoids from Tripterygium wilfordii

Three 18(4→3)-abeo-abietanoids, a new natural product and two new compounds, named tripordolides A–C (1–3), were isolated from the leaves of Tripterygium wilfordii. Their structures were elucidated on the basis of their spectroscopic analysis, and the absolute configuration of compounds was confirmed by CD and X-ray crystallographic analysis using anomalous scattering of Cu Kα radiation. Compounds 1 and 3 showed moderate inhibitory activities against NO production in lipopolysaccharide-induced (LPS) RAW 264.7 macrophages in vitro.

Neuroprotective Dihydroagarofuran Sesquiterpene Derivatives from the Leaves of Tripterygium wilfordii

Thirteen dihydroagarofuran derivatives, including 12 new sesquiterpenoid esters and one known sesquiterpenoid alkaloid, were obtained from the leaves of Tripterygium wilfordii. Spectroscopic techniques and the ECD method were used for the structure elucidation of the compounds. The structures of compounds 1 and 8 were confirmed by single-crystal X-ray crystallographic analyses. Compounds 8, 9, 11, 12, and 13 increased cell viability of the okadaic acid treated PC12 cells from 60.4 ± 23.0% to 72.4 ± 14.1, 71.5 ± 11.5, 75.7 ± 15.6, 81.2 ± 13.1, and 86.2 ± 25.5% at 10 μM, respectively.

Chemical constituents from the roots of Tripterygium wilfordii and their cytotoxic activity

In our ongoing search for bioactive constituents, a new sesquiterpene polyol ester, named triptersinine U (1), together with five known triterpenes (2-6) and seven sesquiterpene pyridine alkaloids (7-13), were isolated from the roots of Tripterygium wilfordii Hook. f. Their chemical structures were elucidated using extensive spectroscopic analyses, including 1D and 2D NMR, and HRESIMS, as well as comparison with previously reported data. Cytotoxic activities of all compounds 1-13 were evaluated against six human tumor cell lines (HepG2, Hep3B, Bcap37, U251, MCF-7 and A549) using the MTT in vitro assay. The results showed that triterpenes exhibited moderate cytotoxic activities toward the tested cell lines.

Prenylated flavonoids from the stems and roots of Tripterygium wilfordii

Phytochemical investigation on the stems and roots of Tripterygium wilfordii led to the isolation and characterization of three new prenylated flavanones, tripteryols A-C (1-3), along with (±)-5,4'-dihydroxy-2'-methoxy-6',6″-dimethypyraro-(2″,3″:7,8)-6-methyflavanone (4), and ((2S)-5,7,4'-trihydroxy-2'-methoxy-8,5'-di(3-methyl-2-butenyl)-6-methylflavanone (5). Structures of the compounds 1-5 were elucidated using spectroscopic techniques, such as UV, IR, NMR (1D and 2D), and HRESI-MS. Tripteryols B (2) was found active in the antimicrobial assay against Cryptococcus neoformans, Pseudomonas aeruginosa, vancomycin-resistant Enterococcus faecalis (VRE) and methicillin-resistant Staphylococcus aureus (MRSA) with IC₅₀ values in the range of 2.95-8.59μg/mL. Compounds 4 and 5 showed significant antimicrobial activities against C. neoformans, MRSA and Staphylococcus aureus with IC₅₀ values in the range of 1.06-2.60μg/mL. Additionally, significant antimalarial activities of tripteryols A-B (1-2) against chloroquine-sensitive D6 and resistant W2 clones of Plasmodium falciparum were observed and none of the compounds 1-5 were cytotoxic to Vero cells.