Banca de DEFESA: JANIELE ALVES EUGÊNIO RIBEIRO GALVÃO

Obtaining the Extract of Aranto leaves (Kalanchoe laetivirens) with supercritical CO2 and Ethanol.

Kalanchoe laetivirens, supercritical extraction, CO₂, ethanol, quercetin.

Aranto (Kalanchoe laetivirens) is an Africa’s native succulent plant, which is present on several continents. Easy to propagate, it contains bioactive compounds such as phenolic compounds and bufadienolides. Used as a natural remedy, there is still no unanimity regarding its pharmacological effectiveness. However, recent studies indicate that its components have anti-inflammatory, antitumor and analgesic activity. In this context, extraction with supercritical CO₂ appears as an alternative for obtaining these components, as it avoids the degradation of bioactives, in addition to being a quick extraction that allows for a purer extract. Furthermore, in some cases the use of cosolvents is necessary due to their solubility with the component of interest and also the viscosity of the extract. That said, ethanol was used in all the experiments. The operating conditions for the tests were developed in a pressure range of 80 to 140 bar, a temperature of 35 to 65° C and a mass ratio between aranto and ethanol of 0.58 to 1.75, with a fixed extraction time of 30 minutes and a previously defined bed particle size with an average diameter of 1.15 mm, making up a 2³ factorial design with a triplicate at the central point. The extract was characterized in terms of antioxidant power by sequestering the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical and the content of phenolic compounds by the Folin-Ciocalteu spectrophotometric method. In addition, the following was identified and quantified in the samples, quercetin, via HPLC (High Performance Liquid Chromatography). The mass yields obtained in the extractions ranged from 0.48 to 2.19%, with the best results being obtained at 65 °C, 80 bar and a ratio of 0.58. According to the statistical analysis of the yield results, the concentration of the solvent had a significant effect. In the Soxhlet extractions, a yield of 19.05% was found using dried aranto leaves and ethanol as the solvent. However, a yield of 0.97% was observed using the fresh leaves of the respective plant, due to the 95.9% moisture content. The results of the quercetin quantification of the samples ranged from 1.03 to 31.96 mg/L. The antioxidant content of the best supercritical extraction condition resulted in an EC50 value (effective concentration that reduces 50% of free radicals) of 22.86 µg/ml, while the sample from the conventional extraction of the dried leaves with ethanol resulted in values of 114.26 µg/ml. With regard to the content of phenolic compounds, the best condition showed 65.73 mg EAG/g Extract (EAG - Gallic Acid Equivalents), while the soxhlet extractions showed 83.28 and 89.09 mg EAG/g Extract from the fresh and dried leaves respectively.