Meicheng Wang

Diterpenes inhibiting NO production from Euphorbia helioscopia

Three new jatrophane diterpenes (1-3), an unreported spectroscopic data jatrophane diterpenene (4), and nine known analogues (5-13) have been isolated from the whole plants of Euphorbia helioscopia. Their structures were established by detailed spectroscopic data analyses (IR, ESIMS, HR-ESIMS, and 1D and 2D NMR), and the structure of 1 was confirmed by X-ray crystallography. The diterpenes showed inhibitory activities on LPS-induced NO production in murine microglial BV-2 cells.

Two novel clerodane diterpenenes with NGF-potentiating activities from the twigs of Croton yanhuii.

Nerve growth factor (NGF) and analog reagents to promote the neurite outgrowth of nerve cells against the neuron degeneration are expected to be potentially useful for the medical treatment of Alzheimers disease. In our focus on the discovery of bioactive diterpenes, we investigated the chemical constituents of the plant Croton yanhuii. This investigation led to the isolation and identification of two novel clerodane diterpenes (1 and 2). Their structures were elucidated on the basis of extensive 1D and 2D NMR (COSY, HMQC, HMBC, and NOESY) and mass (ESIMS and HR-ESIMS) spectroscopic data analyses. Further biological screenings showed that both of the compounds enhanced NGF-mediated neurite outgrowth from PC12 cells.

Isolation, characterization, and neuroprotective activities of sesquiterpenes from Petasites japonicus.

Neuroprotective reagents to protect the nerve cells against oxidative stress and other damages are potentially effective for the medical treatment of Parkinsons disease. Petasites japonicus, a wild vegetable, belongs to the family Compositae and its extract has shown the neuroprotective effects. A further phytochemical investigation of P. japonicus for neuroprotective substances led to the isolation of eight new (1-8) and two known (9 and 10) sesquiterpenes. Their structures were elucidated on the basis of extensive 1D and 2D NMR (HMQC, HMBC, (1)H-(1)H COSY, and NOESY) spectroscopic data analyses, and the structure of 1 was confirmed by X-ray crystallography. The neuroprotective activities of these sesquiterpenes were evaluated against cobalt chloride (CoCl2)-induced neuronal cell death in human dopaminergic SH-SY5Y cells. Five compounds showed a neuroprotective activity.

Bioactive Clerodane Diterpenoids from the Twigs of Casearia balansae

Eight new clerodane diterpenes, balanspenes A-H (1-8), along with two known analogues (9 and 10), were isolated from the twigs of Casearia balansae. The structures of 1-8 were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analysis, and the absolute configurations of compounds 1, 4, and 7 were confirmed by comparing their experimental CD spectra with those calculated by the time-dependent density functional theory method. Compounds 4-7, 9, and 10 were found to possess the property of being able to stimulate NGF-mediated neurite outgrowth from PC12 cells.

Isolation and characterization of sesquiterpenes from Celastrus orbiculatus and their antifungal activities against phytopathogenic fungi.

Celastrus orbiculatus is an insecticidal plant belonging to the Celastraceae family. In this survey on the secondary metabolites of plants for obtaining bioactive substances to serve agriculture, the chemical constituents of the fruits of C. orbiculatus were investigated. This phytochemical investigation resulted in the isolation of nine new and one known sesquiterpene. Their structures, especially the complicated stereochemical features, were elucidated on the basis of extensive NMR spectroscopic data analyses, time-dependent density functional theory CD calculations, and the CD exciton chirality method. Biological screenings disclosed that these sesquiterpenes showed antifungal activities against six phytopathogenic fungi. The results of our phytochemical investigation further disclosed the chemical components of C. orbiculatus, and biological screening implied that it may be potentially useful to protect crops against phytopathogenic fungi and the bioactive compounds may be regarded as candidate agents of antifungal agrochemicals for crop protection products.

Bioactive Diterpenoids from the Leaves of Callicarpa macrophylla

A phytochemical investigation of the leaves of Callicarpa macrophylla led to the isolation of five new diterpenoids (1-5), macrophypenes A-E, and nine known analogues (6-14). The structures of 1-5 were established on the basis of extensive analysis of NMR spectroscopic data, X-ray diffraction data, and experimental and calculated electronic circular dichroism spectra. Compound 1 is a spiroditerpenoid with a novel skeleton, and compound 5 is a rare ent-abietane diterpenoid possessing a peroxide bridge. Compounds 1, 5-7, and 11-14 stimulate nerve growth factor mediated neurite outgrowth from PC12 cells.

Characterization and NO Inhibitory Activities of Chemical Constituents from an Edible Plant Petasites tatewakianus

Petasites tatewakianus is an edible plant belonging to the family Compositae. In our continuous search for NO inhibitors, which may be useful for the development of anti-inflammatory agents, the chemical constituents of the leaves of the edible plant P. tatewakianus were investigated. This phytochemical investigation led to the isolation of 3 new (1-3) and 10 known (4-13) sesquiterpenes and 2 other types of known compounds (14 and 15). Their structures were elucidated on the basis of extensive 1D and 2D NMR spectroscopic data analyses, and the absolute configurations of compounds 1 and 3 were confirmed by comparing their experimental CD spectra with those calculated by the time-dependent density functional theory (TDDFT) method. The following biological studies disclosed that these isolated compounds showed inhibitory activities on LPS-induced NO production in murine microglial BV-2 cells. The results of our phytochemical investigation, including two new bakkenolide sesquiterpenes (1 and 2), one new sesquiterpene with an unusual carbon skeleton (3), and the first report of compounds 5-7 and 10-15 from this species, further revealed the chemical composition of P. tatewakianus as an edible plant, and the biological studies implied that P. tatewakianus, containing bioactive substances with the inhibitory activities of NO production, was potentially beneficial to human health.

Isolation, Characterization, and Antiproliferative Activities of Eudesmanolide Derivatives from the Flowers of Inula japonica.

Inula japonica belongs to the family Asteraceae, and its flowers have been used as dietary supplements and health tea in China. The study aimed to identify the bioactive components with the antiproliferative property. Ten 1,10-seco-eudesmanolide derivatives, including four new compounds (1-4), were isolated from the flowers of I. japonica. Their structures were established on the basis of the interpretation of spectroscopic data and electronic circular dichroism (ECD) calculations. All of these isolates were evaluated for their antiproliferative activities against MCF-7 and MDA-MB-231 human breast cancer cells. Compound 4 possessed the most potent effects, with the IC50 values of 0.20 ± 0.04 and 6.22 ± 1.30 μM against MCF-7 and MDA-MB-231 cells, respectively. The present investigation indicated that eudesmanolide derivatives from the flowers of I. japonica, especially compound 4, might be used as potential antitumor chemotherapy agent candidates.

Bioactive ent-Pimarane and ent-Abietane Diterpenoids from the Whole Plants of Chloranthus henryi

Two new ent-pimarane (1 and 2), eight new ent-abietane (3-10) diterpenoids, and eight known analogues (11-18) were isolated from the whole plants of Chloranthus henryi. The absolute configuration of 1 was determined on the basis of single-crystal X-ray diffraction data. Compound 8 represents a class of rare naturally occurring C-14 norabietanes, and compounds 9 and 10 feature rare 13,14-seco-abietane skeletons. Compounds 5, 12, 13, and 15 inhibited the yeast-to-hyphae transition of Candida albicans with IC50 values between 97.3 and 738.7 μM.

Sesquiterpenes from Carpesium macrocephalum inhibit Candida albicans biofilm formation and dimorphism

One new xanthanolide, 4-(2-methybutyryl)-4H-tomentosin (1) was isolated from the whole plant of Carpesium macrocephalum together with nine known sesquiterpenes (2-10), including four eudesmane sesquiterpenes (2, 4, 5, and 10), one guaianolide (3), two xanthanolides (6 and 9) and two carabranolides (7 and 8). Their structures were elucidated on the basis of detailed spectroscopic analyses. All isolates were evaluated for their antifungal activities against the growth, biofilm formation and yeast-hyphal transition in Candida albicans. All compounds lacked the antifungal activity (MIC50>256 μg/ml) except compound 6 with the MIC50 value of 128 μg/ml. However, compounds 3, 5 and 10 strongly inhibited biofilm formation with IC50 values ranging from 15.4 to 38.0 μg/mL, and compounds 1, 3, 4, 6 and 7 inhibited the yeast-to-hyphae morphogenetic transition with the IC50 values between 31.6 and 118.4 μg/mL. The above results indicated that sesquiterpenes from C. macrocephalum may have therapeutic potential for candidiasis as virulence inhibitors.