Medium-Chain Fatty Acids from Eugenia winzerlingii Leaves Causing Insect Settling Deterrent, Nematicidal, and Phytotoxic Effects

(Myrtaceae) is an endemic plant from the Yucatan peninsula. Its organic extracts and fractions from leaves have been tested on two phloem-feeding insects, and , on two plant parasitic nematodes, and , and phytotoxicity on and . Results showed that both the hexane extract and the ethyl acetate extract, as well as the fractions, have strong antifeedant and nematicidal effects. Gas chromatography-mass spectrometry analyses of methylated active fractions revealed the presence of a mixture of fatty acids. Authentic standards of detected fatty acids and methyl and ethyl derivatives were tested on target organisms. The most active compounds were decanoic, undecanoic, and dodecanoic acids. Methyl and ethyl ester derivatives had lower effects in comparison with free fatty acids. Dose-response experiments showed that undecanoic acid was the most potent compound with EC values of 21 and 6 nmol/cm for and , respectively, and 192 and 64 nmol for and , respectively. In a phytotoxicity assay, medium-chain fatty acids caused a decrease of 38-52% in root length and 50-60% in leaf length of , but no effects were observed on . This study highlights the importance of the genus as a source of bioactive metabolites for plant pest management.