Structural Diversification and Biosynthesis of Pesticidal Pyrroline-Derived Alkaloid from <i>Penicillium citrinum</i> SCSIO DF147

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