Neuroprotective Dihydroagarofuran Sesquiterpene Derivatives from the Leaves of Tripterygium wilfordii

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

Undescribed abietane-type diterpenoids and oleanane-type triterpenoids from the stem and branch of Tripterygium wilfordii

Six undescribed abietane-type diterpenoids (tripterydinoids A-F) and five undescribed oleanane-type triterpenoids (tripterytrinoids A-E) were obtained and determined from the stem and branch of Tripterygium wilfordii Hook. f. (Celastraceae). Tripterydinoids A-C possessed the abietane-type diterpenoid skeleton with rare 8, 9-epoxy ring. The structures of undescribed compounds were established by extensive spectroscopic studies [HRESIMS, 1D/2D-NMR and electronic circular dichroism (ECD) calculation]. The absolute configurations of tripterydinoids A, B, E and tripterytrinoid A were defined by X-ray crystallographic analyses. Bioactivity screening indicated that tripterydinoids A-C exhibited potent inhibitory effects against NO release in LPS-activated RAW 264.7 macrophages with IC₅₀ values of 6.93, 4.46 and 2.98 μM, respectively. Meanwhile, tripterydinoids A-D and tripterytrinoids B, C showed moderate and selective cytotoxicities against five human tumor cell lines (A375, Huh7, MCF-7, HCT-116 and NCI-H460).

Nine new dihydro-β-agarofuran sesquiterpene polyesters from the leaves of Tripterygium wilfordii

Nine previously undescribed dihydro-β-agarofuran type sesquiterpene polyesters, tripteresters A–I (1–9) were isolated from the leaves of Tripterygium wilfordii.

Sesquiterpenoids with neuroprotective activities from the Chloranthaceae plant Chloranthus henryi

A rare sesquiterpenoid possessing a 6/6 bicyclic system fused with two clustered furan units and a pair of guaiane-type sesquiterpenoids were acquired from the roots of Chloranthus henryi. Their structures with absolute configurations were characterized with spectroscopic data, ECD, and X-ray diffraction analysis. All three sesquiterpenoids showed moderate neuroprotective activities on PC12 cells damaged with hydrogen peroxide.

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.

Dihydro-β-agarofuran sesquiterpenoid derivatives with neuroprotective activity from the leaves of Tripterygium wilfordii

A phytochemical investigation on the leaves of Tripterygium wilfordii Hook. F. was conducted, leading to the isolation of five undescribed dihydro-β-agarofuran sesquiterpenoids (1-5) and one known analogue (6). Their structures were determined by comprehensive spectroscopic analyses. The absolute configurations of the compounds were determined by comparison of the experimental ECD with the calculated data. In addition, all the compounds were evaluated for their neuroprotective activities against H₂O₂-induced cell injury in human neuroblastoma SH-SY5Y cells, and 3 showed the better protective effect with 76.63% cell viability comparing with the positive control Trolox (69.84%) at 12.5 μM.

Neuroprotective racemic germacranolides from the roots of Chloranthus henryi

Three pairs of new germacranolides, (+)/(-)-chlogermacrones A-C, along with two known analogues were obtained from the roots of Chloranthus henryi. Spectroscopic techniques and single-crystal X-ray crystallographic analyses were used for the structure elucidation of the compounds. All of the isolated compounds were tested for their neuroprotective effects on H₂O₂ damaged PC12 cells, compounds 3 and 5 increased cell viability from 43.4 ± 1.3% to 99.6 ± 8.7 and 68.1 ± 4.8% at 10 μM, respectively.

Dihydroagarofuran sesquiterpenoid derivatives from the leaves of Tripterygium wilfordii with potential neuroprotective effects against H2O2-induced SH-SY5Y cell injuries

In this study, eight undescribed sesquiterpenoid esters and four known analogues were isolated and their absolute configurations were determined by ECD calculations and single-crystal X-ray diffraction analysis.

Tripterfordins A-O, Dihydro-β-agarofuran Sesquiterpenoids from the Leaves of Tripterygium wilfordii

Fifteen new dihydro-β-agarofuran-type sesquiterpenoids, tripterfordins A-O, were obtained from the aqueous EtOH extracts of the leaves of Tripterygium wilfordii. These constituted a class of highly oxygenated tricyclic sesquiterpenoid polyesters with a cinnamoyloxy group at C-1. The assignments of their structures were conducted via extensive analyses of the spectroscopic data and comparison of experimental and calculated ECD data. The absolute configurations of compounds 1, 4, 9, and 10 were established via single-crystal X-ray diffraction data. Additionally, compounds 1, 4, 9, 10, and 13 exhibited pronounced inhibitory effects on nitric oxide production in RAW 264.7 murine macrophages stimulated by lipopolysaccharide with IC₅₀ values ranging from 11.9 to 31.0 μM.

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.

Anti-inflammatory abietanes diterpenoids isolated from Tripterygium hypoglaucum

Tripterygium hypoglaucum (H. Lév.) Hutch. has been used to remedy rheumatoid arthritis, however, it shows frequent toxicity to the body. In this study, liquid chromatograph-mass spectrometer (LC-MS) was guided to characterize abietanes diterpenoids with anti-inflammatory activity from the stem of T. hypoglaucum. Thirteen undescribed abietanes diterpenoids were isolated and purified, and their chemical structure was identified using various spectroscopic methods. These compounds belonged to abietanes with splitting C ring, abietanes with benzenoid rings, diterpene quinoids, diterpene quinoids with lactone rings, and abietanes with benzenoid and lactone rings, respectively. Lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 macrophages was used to evaluate anti-inflammatory activity of the compounds. The results indicated that hypoglicin B-G and hypoglicin J-M exhibited inhibitory activity of NO production with the IC₅₀ values of 6.01, 25.21, 8.29, 3.63, 0.72, 0.89, 36.91, 0.82, 2.85, 11.92 μM, respectively. Among these compounds, compound hypoglicin L showed high anti-inflammatory activity and low toxicity (SI = 5.02 × 10⁴). Further QPCR analysis revealed that hypoglicin D and hypoglicin L can inhibit the mRNA expression of iNOS in LPS-stimulated RAW264.7 cells at doses of 12.5 and 3.13 μM, respectively. Taken together, ten anti-inflammatory diterpenoids were found from T. hypoglaucum in this study.

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.