Abstract
New asteltoxins U (1) and V (2) were obtained from the solid-state fermentation of Pochonia suchlasporia TAMA 87. The spectroscopic characterization of 1 and 2 revealed that their chemical structures are similar to that of asteltoxin H, except for the modification of the α-pyrone moiety. Specifically, the methyl group on the γ-position of the α-pyrone moiety in asteltoxin H is replaced with a hydroxymethyl group in 1 and 2. In addition, 1 and 2 are a pair of isomers that differ in the geometry of the double bond between C-11 and C-12 in the conjugated triene moiety and that contain an all-trans (9E, 11E, 13E) moiety and a 9E, 11Z, 13E conjugated triene moiety, respectively. Compound 1 showed inhibitory activity toward the first cleavage of sea urchin embryos with a minimum inhibition concentration value of 3.1 µg/mL, whereas compound 2 did not show inhibitory activity up to a concentration of 25 µg/mL.