Ascherxanthone A (1), a novel symmetrical tetrahydroxanthone dimer, was isolated from the entomopathogenic fungus Aschersonia sp. BCC 8401. The structure of 1 was elucidated by spectroscopic analysis, especially 2D-NMR. Compound 1 exhibited activity against Plasmodium falciparum K1 with an IC(50) value of 0.20 microg/mL, but it also showed cytotoxic activities against Vero cells and three tumor cell lines.

[structure: see text]. Vertihemiptellides A (1) and B (2), unique diketopiperazine dimers, were isolated from the insect pathogenic fungus Verticillium hemipterigenum BCC 1449. Structures of these compounds were elucidated by NMR and mass spectral analysis, and the stereochemistry of 1 was determined by X-ray crystallography. The absolute stereochemistry of bisdethiodi(methylthio)-1-demethylhyalodendrin (3), previously isolated from the same fungus, was revised to the (3R,6R) configuration.

Paecilodepsipeptide A (1), a new cyclohexadepsipeptide possessing three d-amino acid residues, together with its linear analogues paecilodepsipeptides B (2) and C (3), was isolated from the insect pathogenic fungus Paecilomyces cinnamomeus BCC 9616. Structures of these compounds were elucidated primarily by NMR and mass spectroscopic analyses. The absolute configurations of the amino acid and hydroxy acid residues of 1 were addressed by HPLC analysis of its acid hydrolyzate using a chiral column and Marfey's method. Paecilodepsipeptide A (1) showed activity against the malarial parasite Plasmodium falciparum K1 with an IC50 value of 4.9 microM. This compound also showed cytotoxicity to two cancer cell lines, KB (IC50 5.9 microM) and BC (IC50 6.6 microM); however, it was inactive against noncancerous Vero cells up to 67 microM (50 microg/mL).

Fourteen new compounds, oudemansins 1–4, oudemansinols 5–7, favolasins 8–10, favolasinin (12), polyketides 13–15, and (R,E)-2,4-dimethyl-5-phenyl-4-pentene-2,3-diol (16), together with nine known compounds were isolated from the basidiomycete fungus Favolaschia sp. BCC 18686. Two new compounds, favolasin E (11) and 9-oxostrobilurin E (17), were isolated from the closely related organism Favolaschia calocera BCC 36684 along with nine β-methoxyacrylate-type derivatives. Compounds in the class of oudemansins and strobilurins exhibited moderate to strong antimalarial activity with relatively low cytotoxicity against Vero cells (African green monkey kidney fibroblasts). Potent antimalarial activity was demonstrated for 9-methoxystrobilurins G, K, and E (IC50 values 0.061, 0.089, and 0.14 μM, respectively). The structure–activity relationships (SAR) for antimalarial activity is proposed on the basis of the activity of the new and several known β-methoxyacrylate derivatives in combination with the data from previously isolated compounds. Furthermore, several compounds showed specific cytotoxicity against NCI-187 cells (human small-cell lung cancer), although the SAR was different from that for antimalarial activity.