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 ( Of ChtII and Of Chi-h) inhibition, revealing that both the 3-pyrroline ring and the Δ 8′,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.