Effect of Thymol and Carvacrol Encapsulated in Hp-Β-Cyclodextrin by Two Inclusion Methods against Geotrichum citri-aurantii.

ABSTRACT

Geotrichum citri-aurantii causes sour rot in citrus fruits and is responsible for important economic losses during storage. However, the availability of chemical fungicides for the control of this pathogen is limited. Thus, the aim of this research was to evaluate the antifungal efficacy of thymol and carvacrol encapsulated in 2-hydroxylpropyl-beta-cyclodextrin (HP-ß-CD) (prepared by the microwave irradiation method [MW] and solubility method [S]) for inhibition of G. citri-aurantii using in vitro bioassays broth (micro and macrodilutions methods) and inoculated food testing. Both encapsulated thymol and carvacrol were shown to be effective for inhibiting G. citri-aurantii growth in in vitro assays. Thymol was more effective in inhibiting G. citri-aurantii, while better encapsulation was provided by MW. HP-ß-CD-thymol encapsulated by MW (HP-ß-CD-thymol-MW) showed the lowest 50% effective dose (ED50 = 1.16 mM), minimum inhibitory concentration (MIC = 5.06 mM), and minimum fungicide concentration (MFC = 52.6 mM). HP-ß-CD-thymol-MW was found highly effective in reducing the growth rate and mycelial growth inhibition. Finally, HP-ß-CD-thymol-MW and HP-ß-CD-carvacrol-MW showed a higher persistent effect than thymol and carvacrol in their natural form in inhibiting this fungus. Therefore, HP-ß-CD-thymol-MW could be a promising alternative to synthetic fungicides for controlling G. citri-aurantii, the causal agent of citrus sour rot. PRACTICAL APPLICATION Encapsulated thymol and carvacrol in HP-ß-Cyclodextrins are effective for controlling G. citri-aurantii in in vitro experiments. Encapsulation of thymol and carvacrol by microwave irradiation method (MW) was more effective than the solubility (S) method. Thymol was more effective than carvacrol, and the best results on G. citri-auriantii inhibition were achieved using the HP-ß-CD-thymol-MW method (which gave the lowest ED50 , MIC, and MFC).