Esterification with a Long-Chain Fatty Acid Elevates the Exposure Toxicity of Tigliane Diterpenoids from Euphorbia fischeriana Roots against Nematodes

In this study, two tigliane diterpenoids, 12-deoxyphorbol-13-hexadecanoateand 12-deoxyphorbol-13-acetate (prostratin), were identified fromthe methanol extract of the roots of Euphorbia fischeriana and were found to have the ability to significantly reduce the survivalof Caenorhabditis elegans. It was determined thatexposure to these two compounds had toxic effects on the growth, reproduction,locomotion behavior, and accumulation of lipids and lipofuscin ofthe nematodes. Moreover, the transcription levels of the genes associatedwith lipid accumulation, apoptosis, insulin, and nuclear hormone synthesisin C. elegans were significantly influenced. Interestingly,12-deoxyphorbol-13-hexadecanoate produced exposure toxicity at lowerconcentrations than that of prostratin. Pearson correlation analysisindicates that the elevated exposure toxicity of 12-deoxyphorbol-13-hexadecanoatemay be the result of differing transcription levels, which resultfrom the differential expression of fat-6, egl-38, and cep-1. These results revealthat esterification with a long-chain fatty acid elevates the exposuretoxicity of this tigliane diterpenoid, thus providing a basis forthe application of tigliane diterpenoids in plant-derived nematicides.