Structural Diversification and Biosynthesis of Pesticidal Pyrroline-Derived Alkaloid from Penicillium citrinum SCSIO DF147.

The pyrroline-derived alkaloid N-(2-methyl-3-oxodec-8-enoyl)-2-pyrroline (MOEP, 1) is a potential pesticide that remains to be structurally diversified for target screening and biosynthesis studies. Bioactivity-guided investigation of the marine-derived fungus Penicillium citrinum SCSIO DF147 yielded five classes of pyrroline-derived alkaloids (1-15), including five new compounds (2-4, 14, and 15). These compounds were first evaluated for chitinase (OfChtII and OfChi-h) inhibition, revealing that both the 3-pyrroline ring and the Δ8',9' double bond are key functional groups. Pesticidal and fungicidal evaluation highlighted compound 1, which outperformed the positive control diflubenzuron against the lepidopteran pest Plutella xylostella, causing 100% larval mortality after 5 days of feeding at 5 mM. The biosynthetic gene cluster (pasA-D) for 1 was identified and characterized. The cytochrome P450 PasB was shown to catalyze the final tailoring step, transforming intermediate 8 into the 3-pyrroline functional group in 1 via dehydroxymethylation and dehydrogenation. These findings provide insights for developing new chitinase-targeting pesticides.