Encapsulation of Ruta essential oil in chitosan and alginate matrices as an ecological alternative for the control of nematodes

Duvan Fernando Castillo, Rubén Albeiro Sánchez-Andica, Brayan Fernando Enriquez, Jaime Restrepo, Martha Isabel Páez-Melo

Preparation and evaluation of new formulations based on the encapsulation of Ruta essential oil (REO) in chitosan (CHS-REO) and alginate (ALG-REO) biopolymeric matrices for its potential use as a nematicide of the genus Meloidogyne spp. Controlled release formulations of REO obtained by ionic gelation were characterized by Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), Zeta Potential, and thermal analysis. Their swelling (Sw) and release rate (RR) were evaluated at different pH, with their corresponding nematicidal activity. Encapsulation efficiencies of 33.4 ± 2.4% (w/w) for ALG-REO and 37.7 ± 3.7% (w/w) with CHS-REO were obtained. The presence of REO in the capsules was evidenced by FTIR and thermal analysis. Release studies revealed that in acidic conditions (pH 4.2), the CHS-REO particles reached a Sw of 240% (w/w) in 30 days and 101% (w/w) for ALG-REO particles, generating a RR of 23.7% for CHS-REO and 20.4% for ALG-REO. On the other hand, at pH 6.8 it favored the Sw for ALG-REO (840% (w/w)) and therefore the RR (45.6%) and disfavored the Sw of CHS-REO generating low RR (16.9%). It was shown that the highest nematicidal effectiveness against the nematode Meloidogyne spp. of the formulations evaluated was that generated by ALG-REO in the Palmira soil and CHS-REO in the Santander soil, possibly due to the pH of each soil. The highest nematicidal efficacy of REO was achieved when it was in encapsulated form and not in free form and this efficacy did not present differences in nematicidal activity (P <0.05) in contrast with the synthetic control nematicide without having a phytotoxic effect on the plant. This study revealed that REO encapsulated in biopolymeric matrices can be used as new nematicidal formulations.