RESUMEN
In this study, poly (lactic-co-glycolic) acid (PLGA) particles were synthesized and coated with chitosan. Three essential oil (EO) components (eugenol, linalool, and geraniol) were entrapped inside these PLGA particles by using the continuous flow-focusing microfluidic method and a partially water-miscible solvent mixture (dichloromethane: acetone mixture (1:10)). Encapsulation of EO components in PLGA particles was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction, with encapsulation efficiencies 95.14%, 79.68%, and 71.34% and loading capacities 8.88%, 8.38%, and 5.65% in particles entrapped with eugenol, linalool, and geraniol, respectively. The EO components' dissociation from the loaded particles exhibited an initial burst release in the first 8 h followed by a sustained release phase at significantly slower rates from the coated particles, extending beyond 5 days. The EO components encapsulated in chitosan coated particles up to 5 µg/mL were not cytotoxic to bovine gut cell line (FFKD-1-R) and had no adverse effect on cell growth and membrane integrity compared with free EO components or uncoated particles. Chitosan coated PLGA particles loaded with combined EO components (10 µg/mL) significantly inhibited the motility of the larval stage of Haemonchus contortus and Trichostrongylus axei by 76.9%, and completely inhibited the motility of adult worms (p < 0.05). This nematocidal effect was accompanied by considerable cuticular damage in the treated worms, reflecting a synergistic effect of the combined EO components and an additive effect of chitosan. These results show that encapsulation of EO components, with a potent anthelmintic activity, in chitosan coated PLGA particles improve the bioavailability and efficacy of EO components against ovine gastrointestinal nematodes.
RESUMEN
The anthelmintic effects of extracted coriander oil and five pure essential oil constituents (geraniol, geranyl acetate, eugenol, methyl iso-eugenol, and linalool) were tested, using larval motility assay, on the third-stage larvae (L3s) of Haemonchus contortus, Trichostrongylus axei, Teladorsagia circumcincta, Trichostrongylus colubriformis, Trichostrongylus vitrinus and Cooperia oncophora. Coriander oil and linalool, a major component of tested coriander oil, showed a strong inhibitory efficacy against all species, except C. oncophora with a half maximal inhibitory concentration (IC50) that ranged from 0.56 to 1.41% for the coriander oil and 0.51 to 1.76% for linalool. The coriander oil and linalool combinations conferred a synergistic anthelmintic effect (combination index [CI] <1) on larval motility comparable to positive control (20 mg/mL levamisole) within 24 h (p < 0.05), reduced IC50 values to 0.11-0.49% and induced a considerable structural damage to L3s. Results of the combined treatment were validated by quantitative fluorometric microplate-based assays using Sytox green, propidium iodide and C12-resazurin, which successfully discriminated live/dead larvae. Only Sytox green staining achieved IC50 values comparable to that of the larval motility assay. The cytotoxicity of the combined coriander oil and linalool on Madin-Darby Canine Kidney cells was evaluated using sulforhodamine-B (SRB) assay and showed no significant cytotoxic effect at concentrations < 1%. These results indicate that testing essential oils and their main components may help to find new potential anthelmintic compounds, while at the same time reducing the reliance on synthetic anthelmintics.