Microencapsulation of rosemary Rosmarinus officinalis essential oil by Chitosan - gum Arabic and its application for the control of two secondary pests of stored cereals

Abstract

Encapsulation of Rosmarinus officinalis essential oil (EO) on chitosan and gum Arabic matrix were prepared at different ratios with various concentrations of essential oil. The capsules were characterized by their encapsulation efficacy (EE%) and loading capacity (LC%). The cumulative release profiles were evaluated by UV/Vis spectroscopy. The chemical compounds for free and encapsulated essential oil were determined by GC-MS technique and the insecticidal toxicity against Tribolium castaneum and Oryzeaphilus surrinamensis was determined by fumigant bioassays. Results showed that capsules with ratio chitosan: gum arabic: EO (1: 1: 0.5) revealed the highest EE (45.8%) and LC (2.31%). In vitro release profiles demonstrated that encapsulated essential oil showed a sustained release especially for the ratio with high EO concentration. The major constituents of the rosemary essential oil were 1,8-cineole (39.67%), Camphor (18.04%), followed by borneol (10.52%) and α-Pinene (6.33%). After encapsulation numerous minor compounds have been missing during storage periods until identifying only 1, 8-cineole, α-terpineol and camphor after 60 days of storage. The fumigant tests demonstrated that encapsulated EO exhibited an effective control against insect pest during storage periods namely 30, 45, 60 days with 99%, 66%, 46% for T. castaneum and 100%, 84%, 82% for O. surrinamensis. This work supports the hypothesis that major essential oil components were responsible for its pesticidal activities over storage. Besides, toxicities against T. castaneum and O. surinamensis adults was mainly attributed to 1, 8-cineole.

Chitosan as a Control Tool for Insect Pest Management: A Review

“…In fact, in Soltani and co-authors [42], fumigation tests with nanocapsules of chitosan loaded with Rosmarinus officinalis EO showed an extension of mortality over time of T. castaneum (20% mortality after 60 days compared to the pure EO after the same time, at 2.1%). These results were confirmed by Soltani and co-authors [43,44], who reported that the rosemary oil nanoencapsulated by chitosan exhibited 82% and 50.7% mortality after 60 days against Oryzaephilus surinamensis (Linnaeus, 1758) (Coleoptera, Silvanidae) and Carpophilus hemipterus (Linnaeus, 1758) (Coleoptera, Nitidulidae) compared to the neat EO (62% and 19% mortality, respectively). Following these results, the EO nanoencapsulation in chitosan was more effective than the neat EO even over time.…”