Shu-Qi Wang

Scaparvin A, A Novel Caged cis-Clerodane with an Unprecedented C-6/C-11 Bond, and Related Diterpenoids from the Liverwort Scapania parva

A novel caged cis-clerodane diterpenoid, scaparvin A, possessing an unprecedented C-6/C-11 bond and a ketal ring, as well as four new cis-clerodane derivatives, scaparvins B-E, were isolated from the Chinese liverwort Scapania parva. Their absolute structures were elucidated by analysis of NMR and CD data coupled with electronic circular dichroism (ECD) calculations. It was proposed that an enzymatic intramolecular aldol reaction was the key step in the biogenetic pathway of scaparvin A.

Stereochemistry of flavonoidal alkaloids from Dracocephalum rupestre

Phytochemical studies on the aerial parts of Dracocephalum rupestre led to the isolation of four groups of flavonoidal alkaloids, dracocephins A-D. They were elucidated as conjugates of flavanone with pyrrolidin-2-one on the basis of extensive spectroscopic analysis. The two stereogenic centers rendered each group of the dracocephins as two pairs of enantiomers simultaneously. All of the sixteen isomers were separated successfully by chiral HPLC and their stereochemical features were determined by their CD data and single-crystal X-ray diffraction analysis of one stereoisomer. The additive relation of the chiroptical contributions resulting from the two stereogenic centers was generalized. The CD contribution of the chiral carbon in the pyrrolidin-2-one ring was proposed by subtraction of their respective contributions.

ent-Kaurane Diterpenoids from Chinese Liverworts and Their Antitumor Activities through Michael Addition As Detected in Situ by a Fluorescence Probe

It is generally accepted that the origin of the cytotoxicity of ent-kaurane diterpenoids is due to the formation of reactive oxygen species (ROS) and that the α,β-unsaturated carbonyl is a pivotal moiety. Herein we demonstrate the isolation of 32 new and 12 known ent-kaurane diterpenoids from two Chinese liverworts. These compounds and three semisynthesized derivatives were screened against human cancer cell lines. The results revealed that their anticancer activities are caused by ROS formation through Michael modification of the protein thiols and depletion of glutathione unselectively. We also found that N-acetylcysteine reverses the cytotoxicity of these diterpenoids by forming Michael adducts, not through a well-recognized ROS scavenging pathway as previously reported. In situ intracellular thiol detection helped us visualize the intracellular distribution of the diterpenoids and determine the potency of their cytotoxicity. An alkaline analogue was found to be more selective because of the altered subcellular distribution.

Phenolic compounds with NF-κB inhibitory effects from the fungus Phellinus baumii

Chemical investigation of the fungus Phellinus baumii has resulted in characterization of five previously undescribed hispidin derivatives, phellibaumins A-E (1-5), as well as two pairs of new non-equivalent epimeric benzyl dihydroflavones, methylphelligrin A (9), epi-methylphelligrin A (10), methylphelligrin B (11), and epi-methylphelligrin B (12), together with five known compounds, interfungin B (6), phelligridin H (7), phelligridimer A (8), phelligrin A (13), and epi-phelligrin A (14). Phellibaumin A (1) was a novel hispidin derivative with a unique 3,4-dihydroxybenzofuran unit. These compounds exhibited NF-κB inhibitory activity with IC(50) values of 52.96 μM (1), 41.40 μM (2), 52.92 μM (5), 36.44 μM (9 and 10), and 22.46 μM (11 and 12), respectively.

Flavonoids from Malus hupehensis and their cardioprotective effects against doxorubicin-induced toxicity in H9c2 cells

Three biflavonoid glycosides along with 12 known flavonoids, were isolated from leaves of Malus hupehensis. The complete structures of two of the compounds were established from analysis of MS, NMR spectroscopic and CD data, as well as DFT CD calculations they were determined to be atropisomeric along a central biaryl axis. The antioxidant activities and protective effects of the compounds against doxorubicin-induced cardiomyopathy in H9c2 cells were also investigated. Amongst all of the isolated compounds, quercetin was the most active radical scavenger with EC(50) values of 3.2 μM and 17.8 μM by the DPPH and ABTS(+) methods, respectively. The results indicated that three of the flavanoids also had a strong protective influence against doxorubicin-induced cell death with EC(50) values of 8.3, 5.2 and 7.6 μM, respectively.

Dracotanosides A-D, spermidine glycosides from Dracocephalum tanguticum: structure and amide rotational barrier.

Four new spermidine glycosides, dracotanosides A-D (1-4), have been isolated from Dracocephalum tanguticum. These molecules represent the first spermidine glycosides from this plant genus. The structures, including absolute configurations, were determined by spectroscopic and chemical methods. The amide bond rotational barrier of aglycone 1a was calculated by density functional theory (DFT) computation.

Cytotoxic clerodane diterpenoids from the leaves and twigs of Casearia balansae.

Ten new clerodane diterpenoids (1-10), caseabalansins A-G, 18-epicaseabalansin A, 2-epicaseabalansin B, and 2-epicaseabalansin C, one new triterpenoid, balansinone (11), and seven known diterpenoids (12-18) were obtained from the leaves and twigs of Casearia balansae. Compounds 1 and 2 are the first examples of clerodane diterpenoids with an oxygen bridge between C-2 and C-19, and compounds 5-7 are three new diterpenoid artifacts presumably formed during the extraction process. The structures of the new compounds were established on the basis of extensive spectroscopic data, and that of 11 was verified by single-crystal X-ray crystallographic analysis. Compound 15 showed cytotoxic activity against the tumor cell lines PC3, DU145, SKOV3, and A549 with IC₅₀ values of 4.5, 4.3, 5.1, and 5.7 μM, respectively. Compounds 1a, 2a, and 4 showed selective activity against PC3 tumor cells.

Phenolic alkaloids from the aerial parts of Dracocephalum heterophyllum.

Chemical examination of aerial parts of Dracocephalum heterophyllum resulted in isolation of phenolic alkaloids, including two flavonoidal alkaloids, drahebephins A and B, one imidazole alkaloid with a phenolic substituent, drahebenine, together with 15 other known compounds. Their structures were established by extensive spectroscopic data analyses. Due to the stereogenic center in the pyrrolidin-2-one ring, the flavonoidal alkaloids are chiral, although they were isolated as racemates. The enantiomers were separated by HPLC using a chiral phase and stereochemically characterized by circular dichroism (CD) spectroscopy. The structure of compound drahebenine was established by X-ray crystallography.

Diterpenoids from the Chinese Liverwort Heteroscyphus tener and Their Antiproliferative Effects

Four new ent-labdane diterpenoids, heteroscyphins A-D (1-4), and four known diterpenoids (5-8) were isolated from the Chinese liverwort Heteroscyphus tener (Steph.) Schiffn. The absolute configuration of compound 1 was defined by single-crystal X-ray diffraction using Cu Kα radiation. Cytotoxicity tests revealed that compounds 3 and 5 exhibited modest activity against seven cancer cell lines. Compound 5 showed inhibitory effects on prostate cancer (PCa) cell proliferation but with less inhibition on non-neoplastic prostate epithelial cells. Compound 5 markedly caused cell growth arrest at the G0/G1 phase and induced cellular apoptosis through ROS-mediated DNA damage in PCa cells.

Chiral separation of two diastereomeric pairs of enantiomers of novel alkaloid-lignan hybrids from Lobelia chinensis and determination of the tentative absolute configuration

Four novel alkaloid-lignan hybrids, lobechinenoids A-D (1-4), were isolated as a mixture of two diastereomeric pairs of enantiomers from the aerial parts of Lobelia chinensis. These compounds are constituted of the union of a tetrahydroisoquinoline alkaloid and a dihydrobenzofuran neolignan moiety. The structures were determined by detailed analyses of IR, MS and NMR data. These four compounds were characterized as two pairs of enantiomers by on-line chiral high performance liquid chromatography (HPLC)-circular dichroism (CD) analysis. The chiral HPLC separation was accomplished in the normal-phase mode using Chiralpak AD-H, a polysaccharide-derived chiral stationary phase (CSP) and a hexane-ethanol mobile phase. In order to study the chiroptical properties, all of the four single stereoisomers were successfully prepared on an analytical Chiralpak AD-H column and their stereochemical features were determined tentatively based on their CD spectra.