Yunjiang Feng

Flinderoles A−C: Antimalarial Bis-indole Alkaloids from Flindersia Species

With the aim of finding new natural product antimalarials, the novel indole alkaloids flinderole A-C were found to have selective antimalarial activities with IC(50) values between 0.15-1.42 microM. Flinderole A was isolated from the Australian plant Flindersia acuminata and flinderoles B and C from the Papua New Guinean plant F. amboinensis. Flinderoles A-C contain an unprecedented rearranged skeleton compared to their related isomers of the borreverine class of compounds.

Clavatadine A, A Natural Product with Selective Recognition and Irreversible Inhibition of Factor XIa †

Bioassay-guided fractionation of a CH2Cl2/MeOH extract of the sponge Suberea clavata using the serine protease factor XIa to detect antithrombotic activity led to the isolation of the new marine natural products, clavatadines A and B. Clavatadines A and B inhibited factor XIa with IC50s of 1.3 and 27 microM, respectively. A crystal structure of protein-inhibitor (clavatadine A) complex was obtained and revealed interesting selective binding and irreversible inhibition of factor XIa. The cocrystal structure provides guidance for the design and synthesis of future factor XIa inhibitors as antithrombotic agents.

Antitrypanosomal Cyclic Polyketide Peroxides from the Australian Marine Sponge Plakortis sp.

Bioassay-guided fractionation of the crude extract from the Australian marine sponge Plakortis sp. led to the isolation of two new cyclic polyketide peroxides, 11,12-didehydro-13-oxo-plakortide Q (1) and 10-carboxy-11,12,13,14-tetranor-plakortide Q (2). Antitrypanosomal studies showed that compound 1 had an IC(50) value of 49 nM against Trypanosoma brucei brucei, and compound 2, where a carboxylic acid is present in the side chain, had a 20-fold reduction of activity. 11,12-Didehydro-13-oxo-plakortide Q (1) is the most active peroxide isolated so far against T. b. brucei, and it indicates the potential therapeutic value of this class of compounds.

Clavatadines C-E, Guanidine Alkaloids from the Australian Sponge Suberea clavata

Three new marine alkaloids, clavatadines C-E (1-3), together with the three known compounds aerophobin 1 (4), purealdin L (5), and aplysinamisine II (6) were isolated from extracts of the sponge Suberea clavata by bioassay-guided fractionation using a serine protease factor XIa assay. Their structures were determined by 1D and 2D NMR spectroscopy. Compounds 1-6 exhibited weak inhibition of factor XIa.

Ianthelliformisamines A–C, Antibacterial Bromotyrosine-Derived Metabolites from the Marine Sponge Suberea ianthelliformis

A high-throughput screening campaign using a prefractionated natural product library and an in vitro Pseudomonas aeruginosa (PAO200 strain) assay identified two antibacterial fractions derived from the marine sponge Suberea ianthelliformis. Mass-directed isolation of the CH(2)Cl(2)/CH(3)OH extract from S. ianthelliformis resulted in the purification of three new bromotyrosine-derived metabolites, ianthelliformisamines A-C (1-3), together with the known natural products aplysamine 1 (4) and araplysillin I (5). The structures of 1-3 were determined following analysis of 1D and 2D NMR and MS spectroscopic data. This is the first report of chemistry from the marine sponge S. ianthelliformis. Ianthelliformisamine A (1) showed inhibitory activity against the Gram-negative bacterium P. aeruginosa with an IC(50) value of 6.8 μM (MIC = 35 μM).

Chemical constituents from Eucalyptus citriodora Hook leaves and their glucose transporter 4 translocation activities.

Bioassay-guided phytochemical investigation of the EtOAc fraction from the leaves of a Chinese medicinal herb, Eucalyptus citriodora Hook, resulted in the isolation of a new compound rhodomyrtosone E (1), along with 12 known compounds (2-13). The structure of the new compound was established by 1D and 2D NMR, MS data and X-ray crystallographic analysis. Betulinic acid (2) and corosolic acid (5) increased glucose transporter 4 (GLUT-4) translocation by 2.38 and 1.78-fold, respectively.

Polydiscamides B-D from a Marine Sponge Ircinia sp. as Potent Human Sensory Neuron-Specific G Protein Coupled Receptor Agonists

Polydiscamides B, C, and D (1-3) were isolated from a sponge Ircinia sp. The structures of 1 to 3 were elucidated by the comparison of their NMR and HRESIMS spectroscopic data with that of a structurally related compound, polydiscamide A. All compounds showed potent agonist activity against human sensory neuron-specific G protein couple receptor (SNSR), a receptor involved in the modulation of pain, and they are the first examples of nonendogenous human SNSR agonists.

Isolation, structure determination and cytotoxicity studies of tryptophan alkaloids from an Australian marine sponge Hyrtios sp.

Mass-guided fractionation of the MeOH extract from a specimen of the Australian marine sponge Hyrtios sp. resulted in the isolation of two new tryptophan alkaloids, 6-oxofascaplysin (2), and secofascaplysic acid (3), in addition to the known metabolites fascaplysin (1) and reticulatate (4). The structures of all molecules were determined following NMR and MS data analysis. Structural ambiguities in 2 were addressed through comparison of experimental and DFT-generated theoretical NMR spectral values. Compounds 1-4 were evaluated for their cytotoxicity against a prostate cancer cell line (LNCaP) and were shown to display IC50 values ranging from 0.54 to 44.9 μM.

Trikentramides A-D, indole alkaloids from the Australian sponge Trikentrion flabelliforme.

Chemical investigations of two specimens of Trikentrion flabelliforme collected from Australian waters have resulted in the identification of four new indole alkaloids, trikentramides A-D (9-12). The planar chemical structures for 9-12 were established following analysis of 1D/2D NMR and MS data. The relative configurations for 9-12 were determined following the comparison of (1)H NMR data with data previously reported for related natural products. The application of a quantum mechanical modeling method, density functional theory, confirmed the relative configurations and also validated the downfield carbon chemical shift observed for one of the quaternary carbons (C-5a) in the cyclopenta[g]indole series. The indole-2,3-dione motif present in trikentramides A-C is rare in nature, and this is the first report of these oxidized indole derivatives from a marine sponge.

Iotrochamides A and B, antitrypanosomal compounds from the Australian marine sponge Iotrochota sp.

Bioassay-guided isolation of the CH(2)Cl(2)/MeOH extract from the Australian sponge Iotrochota sp. resulted in the purification of two new N-cinnamoyl-amino acids, iotrochamides A (1) and B (2). The chemical structures of 1 and 2 were determined by 1D/2D NMR and MS data analyses. Compounds 1 and 2 were shown to inhibit Trypanosoma brucei brucei with IC(50) values of 3.4 and 4.7 μM, respectively.