Encapsulation of Cynara Cardunculus Guaiane-type Lactones in Fully Organic Nanotubes Enhances Their Phytotoxic Properties

The encapsulation of bioactive natural products has emerged as a relevant tool for modifying the poor physicochemical properties often exhibited by agrochemicals. In this regard, natural guaiane-type sesquiterpene lactones isolated from Cynara cardunculus L. have been encapsulated in a core/shell nanotube(c)agrochemical system. Monitoring of the F and O signals in marked sesquiterpenes confirmed that the compound is present in the nanotube cavity. These structures were characterized using scanning transmission electron microscopy-X-ray energy-dispersive spectrometry techniques, which revealed the spatial layout relationship and confirmed encapsulation of the sesquiterpene lactone derivative. In addition, biological studies were performed with aguerin B (1), cynaropicrin (2), and grosheimin (3) on the inhibition of germination, roots, and shoots in weeds (Phalaris arundinacea L., Lolium perenne L., and Portulaca oleracea L.). Encapsulation of lactones in nanotubes gives better results than those for the nonencapsulated compounds, thereby reinforcing the application of fully organic nanotubes for the sustainable use of agrochemicals in the future.

This research was funded by the Agencia Estatal de Investigacion, Ministerio de Ciencia e Innovacion, grant number PID2020-115747RB-I00/AEI/10.13039/501100011033, Spain. F. J.R.M thanks the University of Cadiz for postdoctoral support under grant 2018-009/PU/EPIF-FPI-CT/CP. Furthermore, this work has received financial support from the Junta de Andalucia (FQM334), MINECO/FEDER (projects MAT2017-87579-R). This project has received funding from the European Union's Horizon 2020 research and innovation program under grant 823717-ESTEEM3. STEM studies were performed at the DME Facilities of SCCYT at the University of Cadiz. We also thank Semillas Fito (Barcelona, Spain) for kindly supplying us with wheat seeds.