Herbicidal Polyketides and Diketopiperazine Derivatives from Penicillium viridicatum

Herbicidal activity-guided isolation from the fermentation extract of Penicillium viridicatum had obtained two herbicidal series of polyketides (1–7) and diketopiperazine derivatives (8–11), especially including three novel polyketides (1–3). The structures and absolute configurations of new 1–3 were elucidated by extensive spectroscopic analyses, as well as comparisons between measured and calculated ECD spectra. Novel polyketides 1–3 and known 4, all bearing the heptaketide skeleton with a trans-fused decalin ring of 8-CH3 substitution, could significantly inhibit the radicle growth of Echinochloa crusgalli seedlings with a dose-dependent relationship. Especially at the concentration of 10 μg/mL, 1–4 exhibited the inhibition rates with 81.5% ± 2.0, 76.4% ± 0.8, 79.6% ± 1.1, and 80.0 ± 1.8%, respectively, even better than the common-used synthetic herbicide of acetochlor with 76.1 ± 1.4%. Further greenhouse bioassay revealed that 4 showed pre-emergence herbicidal activity against E. crusgalli with the fr...