Insecticidal Activity of Paraherquamides, Including Paraherquamide H and Paraherquamide I, Two New Alkaloids Isolated from Penicillium cluniae

Paraherquamide H ( 1 ) and paraherquamide I ( 2 ), two new compounds of the paraherquamide (PHQ) family, together with the already known paraherquamide A ( 3 ), paraherquamide B ( 4 ), paraherquamide E ( 5 ), VM55596 ( N -oxide paraherquamide) ( 6 ), paraherquamide VM55597 ( 7 ), and five known diketopiperazines ( 8 − 12 ) have been isolated from the culture broth of Penicillium cluniae Quintanilla. The structure of 1 and 2, on the basis of NMR and MS analysis, was established. It is worth noticing that, in both cases, an unusual oxidative substitution in C-16 was found, which had only previously been detected in PHQ 7 . Isolated compounds were tested for insecticidal activity against the hemipteran Oncopeltus fasciatus Dallas. Mortality data have allowed preliminary structure activity relationships to be proposed. The most potent product was 5 with a LD 50 of 0.089 μg/nymph.