Guo-You Li

Brevianamide J, A New Indole Alkaloid Dimer from Fungus Aspergillus versicolor

Brevianamide J (1), a new indole alkaloid dimer, was isolated together with four new diketopiperazine alkaloids (brevianamide K-N, 2-5) from the solid-state fermented culture of Aspergillus versicolor. Their structures were elucidated on the basis of spectral data. X-ray crystallographic analysis confirmed the structures of 1 and 4.

ent-Kaurane and Cembrane Diterpenoids from Isodon sculponeatus and Their Cytotoxicity

Nine new ent-kauranoids, sculponins D-L (1-9), and 14 known diterpenoids (10-23) were isolated from the aerial parts of Isodon sculponeatus. The structures of the new diterpenoids were determined by detailed interpretation of their 1D and 2D NMR spectra and HRESIMS. The isolated compounds were evaluated for their cytotoxic activities against a small panel of human cancer cell lines.

Calophyline A, a New Rearranged Monoterpenoid Indole Alkaloid from Winchia calophylla

Calophyline A (1), a novel unprecedented rearranged monoterpenoid indole alkaloid, along with a new natural product N-methyl aspidodasycarpine (2) and six known analogues, was isolated from the trunk barks of Winchia calophylla. The structure of compound 1 was elucidated on the basis of spectroscopic data and then confirmed by a single-crystal X-ray crystallographic analysis. A hypothetical biogenetic pathway for compound 1 was proposed. All isolated compounds were evaluated for their in vitro cytotoxicity against a small panel of human cancer cell lines.

Nitrogen-Containing Dihydro-β-agarofuran Derivatives from Tripterygium wilfordii

Thunder god vine, the dried roots of Tripterygium wilfordii, is a widely used traditional Chinese medicine. More than 200 bioactive complex natural products have been isolated from this herb. Inspired by the diversity of chemical structures and bioactivities of the components of this herb, the investigation to mine new chemical entities as potential drug leads led to the identification of 36 nitrogen-containing compounds. Among them, 18 new dihydro-β-agarofuran alkaloids (tripterygiumines A-L (1-12), M-Q (22-26), and R (33)) were identified from the spectroscopic data and chemical degradation studies. Tripterygiumine Q (26) exhibited immunosuppressive activity against human peripheral mononuclear cells with an IC50 value of 8.67 μM and showed no cytotoxicity, even at 100 μM, indicating that 26 may represent a novel scaffold for the development of new immunosuppressants.

Chaetoconvosins A and B, Alkaloids with New Skeleton from Fungus Chaetomium convolutum

Chaetoconvosins A and B (1 and 2), two novel cytochalasan alkaloids with a new 6/6/5/5/7 pentacyclic ring system, were isolated from the solid-state fermented medium of the wheat rhizospheric fungus Chaetomium convolutum cib-100. Their structures were elucidated on the basis of spectroscopic data. The structure of chaetoconvosin A (1) was confirmed by X-ray crystallographic analysis. Chaetoconvosin B (2), the major metabolite, showed remarkable inhibitory ability on root elongation and moderate cytotoxicity against several cancer cell lines.

ent-Kaurane Diterpenoids from Isodon nervosus

A pentacyclic ent-kauranoid, nervonin A ( 1), with an unprecedented cyclobutane moiety in the structure, and nine other new ent-kaurane diterpenoids, nervonins B-J ( 2- 10), along with 10 known ones ( 11- 20), were isolated from Isodon nervosus. Their structures were elucidated by detailed spectroscopic analysis. All diterpenoids were assayed for their cytotoxicity against K562, A549, and HepG2 human cell lines. Compounds 2, 11, 16, 17, and 20 showed significant cytotoxicity.

Electrospray ionization tandem mass spectrometry of chaetoglobosins

RATIONALE Chaetoglobosins are a family of macrocyclic polyketide alkaloids. They possess many similar isomers and exhibit a wide range of biological activities. Thus, there is a need for reliable, fast, and low-cost analysis of this class of compounds. METHODS A series of seven chaetoglobosins from Chaetomium globosum, including two types of isomers, were investigated using electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-QTOF-MS/MS) in both positive- and negative-ion mode. The identity of major product ions was supported by deuterium-labeling experiments. RESULTS In positive-ion mode, the product ion at m/z 130 is the characteristic ion of the indolyl group. A McLafferty rearrangement might play a significant role in the fragmentation of the macrocycle moiety for most chaetoglobosins and produces two series of characteristic product ions, accompanied by neutral losses. The characteristic product ion at m/z 309 in the MS/MS spectrum of chaetoglobosins E indicates the structure of the cyclic olefinic bond in ring B and can be used to distinguish it from the isomers, chaetoglobosins F(ex) , which has an exocyclic double bond on ring B. In negative-ion mode, the McLafferty rearrangement has an important role in the fragmentation pattern of the macrocycle. Some high-abundance radical ions were detected. The radical product ion at m/z 138 might differentiate chaetoglobosins F and penochalasin F, isomers which have very similar structures. CONCLUSIONS In summary, complementary information obtained from fragmentation experiments of [M+H](+) and [M-H](-) precursor ions is especially valuable for rapid identification of chaetoglobosins. The high-abundance radical ions in negative-ion mode are also of scientific interest.

A new sesquiterpene glucoside from Nicotiana rustica L.

A new compound, rel-2R,5S,9S,10R,11R,12-trihydroxy-6(7)-spirovetiven-8-one-9- O -β-D-glucopyranoside (1), along with a known spirovetiven glucoside (2), was isolated from the leaves of Nicotiana rustica L. The structure of compound (1) was elucidated on the basis of spectroscopic data.

A new cyclododeca[d]oxazole derivative from Streptomyces spp. CIBYL1.

A novel secondary metabolite, N-trans-cinnamoyl 2-amino-3a,4,5,6,7,8,9,10,11,12,13,13a-dodecahydrocyclododeca[d]oxazole (1), was isolated from Streptomyces spp. CIBYL1, along with five known compounds, pimprinine (2), (3R,4S,5R,6R)-3,4,5,6-tetrahydro-4-hydroxy-3,5,6-trimethyl-2H-pyran-2-one (3), indolyl-3-carboxylic acid (4), 2-phenylacetamide (5) and di(1H-pyrrol-2-yl)methanone (6). The structures of these metabolites were elucidated on the basis of extensive analysis of spectroscopic data, including OR, IR, HRMS, 1D and 2D NMR data and chemical derivation.

A new bergenin derivative from Corylopsis willmottiae

A new bergenin derivative, 11-O-(3′-O-methylgalloyl)-bergenin, was isolated from the whole plants of Corylopsis willmottiae Rehd. et Wils, along with 11-O-galloylbergenin, 11-O-syringylbergenin, bergenin, 4-O-galloylbergenin, and 4,11-di-O-galloylbergenin. They were identified on the basis of spectral evidence.