New Indole Diketopiperazine Alkaloids from Soft Coral‐Associated Epiphytic Fungus Aspergillus sp. EGF 15‐0‐3

Three new indole diketopiperazine alkaloids, 11‐methylneoechinulin E and variecolorin M, and (+)‐variecolorin G, along with 12 known analogs, were isolated from a soft coral‐associated epiphytic fungus Aspergillus sp. EGF 15‐0‐3. The structures of the new compounds were unambiguously established by extensive spectroscopic analyses including HR‐ESI‐MS, 1D and 2D NMR spectroscopy and optical rotation measurements. The absolute configurations of (+)‐ and (?)‐variecolorin G were determined by experimental and quantum‐chemical ECD investigations and single‐crystal X‐ray diffraction analysis. Variecolorin G is a pair of enantiomeric mixtures with a ratio of 1 : 2. Moreover, (+)‐neoechinulin A is firstly reported as a natural product. The cytotoxic activities of all the isolated compounds against NCI‐H1975 gefitinib resistance (NCI‐H1975/GR) cell lines were preliminarily evaluated by MTT method.     

Possible antagonism of (Z)‐2‐hexenyl (E)‐3‐hexenoate against the attractiveness of (E)‐2‐hexenyl (Z)‐3‐hexenoate to Ooencyrtus nezarae (Hymenoptera: Encyrtidae)

Ooencyrtus nezarae (Hymenoptera: Encyrtidae) is an egg parasitoid of bean bug Riptortus pedestris (Hemiptera: Alydidae) which is a major pest of beans. Females of O. nezarae are attracted to (E)‐2‐hexenyl (Z)‐3‐hexenoate (EZ), one of the components of aggregation pheromone of R. pedestris. Effects of three isomers (ZE, EE and ZZ) of EZ on the attractiveness of O. nezarae were tested using electroantennography (EAG) and field bioassays. EAG analyses revealed that the response of O. nezarae to ZE was significantly higher than those to air, hexane and two other isomers, even though the response was lower than that to EZ. ZE affected the attractiveness of EZ dose‐dependently in the field. Addition of ZE (100 mg) to EZ (10 mg) caused a significant reduction in the catches of O. nezarae females. Single or binary addition of two other isomers (EE and ZZ) to EZ could not decrease or increase significantly the number of O. nezarae catches of EZ. Even though addition of ZZ (10, 50 or 100 mg) to EZ (10 mg) caused dose‐dependent reduction in the number of O. nezarae female catches, the reductions were not significantly different from that of EZ. EZ and its three isomers were not attractive to O. nezarae males at all.