Dichapetalin-type triterpenoids and lignans from the aerial parts of Phyllanthus acutissima

Chemical investigation of the aerial parts of Phyllanthus acutissima resulted in the isolation of five new dichapetalin-type triterpenoids, acutissimatriterpenes A-E ( 1- 5), and two new lignans, acutissimalignans A ( 6) and B ( 7), along with two known lignans and three known ellagic acid derivatives. The structures of 1- 7 were determined mainly on the basis of spectroscopic methods. The compounds obtained were evaluated for cytotoxic and anti-HIV-1 activities.     

Antimycobacterial anthraquinone-chromanone compound and diketopiperazine alkaloid from the fungus Chaetomium globosum KMITL-N0802

Investigation of the fungus Chaetomium globosum KMITL-N0802 led to the isolation of a novel anthraquinone-chromanone compound named chaetomanone along with seven known compounds, ergosterol, ergosteryl palmitate, chrysophanol, chaetoglobosin C, alternariol monomethyl ether, echinuline and isochaetoglobosin D. These compounds were characterized by spectroscopic methods. Chaetomanone and echinulin exhibited activity towards Mycobacterium tuberculosis.     

Azadirachtin derivatives from seed kernels of Azadirachta excelsa

Three new azadirachtin derivatives, named azadirachtins O-Q (1-3), along with the known azadirachtin B (4), azadirachtin L (5), azadirachtin M (6) 11alpha-azadirachtin H (7), 11beta-azadirachtin H (8), and azadirachtol (9) were isolated from seed kernels of Azadirachta excelsa. Their structures were established by spectroscopic techniques, and the structure of 3 was confirmed by X-ray analysis. Compounds 1-7 and 9 exhibited toxicity to the diamondback moth (Plutella xylostella) with an LD50 of 0.75-1.92 microg/g body weight, in 92 h.     

Trishomocubane amino acid as a beta-turn scaffold

The synthesis and X-ray structure of two diasteriomeric heptapeptides [Ac-Ala-Ala-Ala-(R/S)-Cage-Ala-Ala-Ala-NH2] with a trishomocubane amino acid as a beta-turn scaffold are reported. The amino acid was synthesized as a racemate and two diastereomeric peptides were obtained. The two peptides were separated by preparative high-pressure liquid chromatography and crystals suitable for X-ray analysis were grown for both diasteriomeric peptides. In general, both the peptides satisfy the criteria for beta-turn conformations. Five of the six Ala residues of both cage peptide crystals satisfy the criteria for 3(10)-helix characteristics and the cage amino acid residue satisfied the alpha-helix classification. These experimental results confirm previous theoretical studies in our laboratory which predicted that the cage moiety would be a strong/active beta-turn inducer.     

Antiplasmodial sesquiterpene alkaloids from the roots of Maytenus mekongensis

Eight new sesquiterpene alkaloids (1-8) and four known sesquiterpene alkaloids (9-12) have been isolated from the roots of Maytenus mekongensis. Structures were determined using extensive spectroscopic methods. The relative configuration of 7-epi-mekongensine (2) was established by single-crystal X-ray crystallographic analysis. The alkaloids were evaluated for antiplasmodial activity against Plasmodium falciparum, K1 strain, and for cytotoxicity using a panel of cell lines.     

New bioactive prenylflavonoids and dibenzocycloheptene derivative from roots of Dendrolobium lanceolatum

Two new flavanones (1 and 2), a new flavan (3), and a new rare dibenzocycloheptene derivative (4) together with a known flavan, 4'-hydroxy-2' ',2' 'dimethyl-pyranoflavan (5), were isolated from the roots of Dendrolobium lanceolatum. Their structures were established on the basis of spectral evidence, and an X-ray analysis was performed to confirm the structure of 4. Compounds 1-3 exhibited antimalarial activity with IC50 values of 2.6, 3.3, and 3.1 microg/mL, respectively. Compounds 1-5 showed moderate antimycobacterial activity with MIC values of 6.3, 12.5, 25, 25, and 50 microg/mL, respectively. In addition, 1 showed strong cytotoxicity against cancer cell lines KB, BC, and NCI-H187 with IC50 values of 1.2, 1.6, and 0.6 microg/mL, respectively, while 2 showed moderate cytotoxicity against the NCI-H187 cell line with an IC50 value of 8.1 microg/ mL.     

Ketene acetal and spiroacetal constituents of the marine fungus Aigialus parvus BCC 5311

Aigialone (1) and aigialospirol (2), two structurally unique compounds, were isolated from the mangrove fungus Aigialus parvus BCC 5311. The structure of the new ketene acetal 1 was elucidated by spectral analysis, and its relative stereochemistry was determined by X-ray crystallography. The stereochemistry of aigialospirol (2), elucidated by NMR spectral analysis, suggested that this compound is possibly derived from hypothemycin (3), a metabolite previously isolated from this same fungus.     

Antimalarial dihydroisocoumarins produced by Geotrichum sp., an endophytic fungus of Crassocephalum crepidioides

Three novel dihydroisocoumarin derivatives (1-3) with antimalarial, antituberculous, and antifungal activities have been isolated by bioassay-guided fractionation from an endophytic fungus, Geotrichum sp., collected from Crassocephalum crepidioides. Structures were established as 7-butyl-6,8-dihydroxy-3(R)-pent-11-enylisochroman-1-one (1), 7-but-15-enyl-6,8-dihydroxy-3(R)-pent-11-enylisochroman-1-one (2), and 7-butyl-6,8-dihydroxy-3(R)-pentylisochroman-1-one (3) using spectroscopic data.     

Bioxanthracenes from the insect pathogenic fungus Cordyceps pseudomilitaris BCC 1620. II. Structure elucidation

Structures of eleven bioxanthracenes (1 approximately 11) and two monomers (12 and 13), isolated from the insect pathogenic fungus Cordyceps pseudomilitaris BCC 1620, were elucidated. The structure, including the axial stereochemistry, of one of the major symmetrical dimers (1) was determined by X-ray crystallographic analysis, while the stereochemistries of the other isomers were deduced by chemical conversions and spectroscopic means.