Eco-Friendly Crop Protection: Argyrantemum frutescens, a Source of Biofungicides

Plant-derived biopesticides are emerging as a promising and popular alternative for promoting cleaner and safer agricultural practices. The present work aims to explore Argyranthemum frutescens (Asteraceae) as a source of botanical pesticides and to validate this through a cultivation process. To this task, a bioassay-guided fractionation of the ethanolic root extracts from both wild and cultivated A. frutescens on phytopathogenic fungi of Botrytis cinerea, Fusarium oxysporum, and Alternaria alternata was conducted. This approach led to the identification of polyacetylenes with higher potency than commercial fungicides. Specifically, compounds 3 (capillin) and 5 (frutescinone) showed more than 90% growth inhibition at 0.05 mg/mL concentration on B. cinerea, while compounds 2 (capillinol) and 3 were also more active than positive controls, Fosbel-Plus and Azoxystrobin, against F. oxysporum. The structures of the isolated polyacetylenes (1–6, 9, and 10) and alkamides (7, 8, and 11) were determined through spectroscopic analysis, and the absolute configuration of stereocenter C1 of compounds 1, 2, 4 and 9 was determined by NMR-spectroscopy with (R)-(-)-α-methoxy-phenylacetic as a chiral derivatizing agent, and biogenetic considerations. Overall, this study supports the potential of polyacetylenes as promising agrochemical lead compounds against phytopathogens, and validates A. frutescens cultivation as a viable source of biopesticides.