Studies concerning the molecular complexation of Lippia sidoides essential oil in β-cyclodextrin by conventional and ultrasound assisted method

Abstract

Lippia sidoides Cham. is an aromatic herb from Northeast of Brazil, popularly known as pepper-rosmarin. This plant contains an essential oil (EO) with high concentration of thymol and carvacrol; comparable of thyme oil. The presence of these and other bioactive compounds give this specie important antimicrobial, larvicidal, molluscicides, and antioxidant activities. When exposed to oxygen, light or heat, EOs can undergo irreversible alterations in their physicochemical properties. Microencapsulation can be applied to transform these substances into more stable materials (lower volatility and less susceptibility to oxidation) providing easy handling (solid form). Formation of inclusion complexes of EO in cyclodextrins has been reported as an efficient method to improve stability of their terpenoid compounds. There are several complexation methods, and the slurry method followed by water removal by filtration and evaporation or by other drying method (ex. freeze drying or spray drying) is one of the most commonly used. Since the slurry preparation and drying conditions are the key factor involved in the encapsulation efficiency, the aim of this work was to investigate the effects of ultrasound (ultrasound assisted complexation) in the efficiency of formation of inclusion complexes of L. sidoides EO in b-cyclodextrin (b-CD) compared with conventional homogenization technique. The ratio EO:b-CD studied were 1:10 and 2:10, and the solid content of the aqueous slurry set at 30%. The prepared slurries were spray dried at temperature of 160 °C, gas flow rate of 60 m3/h, feed composition flow rate of 4 g/min. EO content, thymol content, product mean diameter, moisture content, and process yield were the responses evaluated. The results showed that the use of ultrasound improved at least 1.2 times the complexation efficiency compared to the conventional homogenization method. The ratio EO:b-CD of 1:10 showed better performance with regard to the total EO retention.