Desenvolvimento de encapsulados de óleo essencial de Syzygium aromaticum (L.) por gelificação iônica e avaliação da atividade antioxidante

Abstract

Considering the need to improve products, improve the thermal stability of volatile compounds and develop complementary pharmacological therapies, this work aimed to develop sodium alginate encapsulates loaded with clove essential oil (Syzygium aromaticum) using techniques ionic gelation and freeze drying. They were prepared encapsulated in different concentrations of essential oil: F1 (1.0%, v/v); F2 (0.5%, v/v); and F3 (0.1%, v/v). A 3.0% (w/v) CaCl2 solution was used for chemical crosslinking with the alginate (1.0% w/v). Encapsulated F1, F2 and F3 were subjected to freeze-drying to obtain encapsulated LF1, LF2 and LF3, respectively. The following techniques were used to characterize the formulations: eugenol release, degree of swelling, GC/MS, SEM, FTIR, TGA/DSC, in addition to analysis of antioxidant power (DPPH and FRAP). Encapsulated F1, F2 and F3 were rounded, rigid to the touch, with color varying from translucent (lower concentration of CEO) to whitish (higher concentration of CEO). Freeze-drying was used in order to remove the aqueous content present in the encapsulates and provide greater thermal stability to the final product. The encapsulated lyophilized products appeared rigid, with a dry, rough and shriveled appearance. The Encapsulation Efficiency (EE%) was high (LF1: 39.3% + 0.79; LF2: 50.4% + 0.63; LF3: 76.9% + 0.51). Eugenol was the majority component identified by GC/MS. The high phenolic content present in the essential oil (449.9 mg E.AG g-1) was preserved in the freeze-dried encapsulates, resulting in important antioxidant activity. The encapsulated LF1 showed the lowest IC50 of 18.1 μg/mL, reaching 80.3% inhibition of the DPPH radical. In the FRAP test, it presented a reducing power of 1,824.6 + 3.5 µmol Fe2+/g, a value close to that of pure essential oil. The three lyophilized encapsulates showed statistical differences in all concentrations analyzed by ANOVA and Tukey's test (p<0.05). The FTIR peaks corresponding to the CEO present in the encapsulates were identified without molecular changes. SEM microscopies showed a low tendency for the formation of agglomerates and rigid particles, with a wrinkled, porous appearance and irregular shapes. In thermal analysis, the LF3 encapsulated was apparently more stable followed by the LF2 and LF1 encapsulated. The degree of swelling was 19.2% (PBS solution). The release of eugenol (92.5%) in PBS solution was faster than in acidic medium. In general, it is concluded that the results are promising and offer a basis for expanding the scope of research into freeze-dried encapsulated essential oils. The low-cost technology used allows the content and characteristics of CEO to be maintained in the three concentrations tested, offering a basis for future research with essential oil encapsulates.