CAROLINA MOSER PARAÍSO

Título da Dissertação: EXTRAÇÃO DOS COMPOSTOS BIOATIVOS DOS CÁLICES DE HIBISCO (Hibiscus sabdariffa L.) ASSISTIDO POR ULTRASSOM VISANDO APLICAÇÃO EM MATRIZ ALIMENTÍCIA

Orientadora: Profa Dra. Grasiele Scaramal Madrona

Data da Defesa: 23/02/2018

RESUMO GERAL

INTRODUCTION
The dried calyxes of Hibiscus sabdariffa L., popularly known as hibiscus or roselle, have a high content of antioxidant substances such as anthocyanins, flavonoids and phenolic acids capable of reducing the risk of certain diseases. Due to the importance of the different bioactive compounds present in the hibiscus calyxes, extraction by ultrasound appears as a more efficient alternative to conventional methods to obtain vegetal extracts. In addition, this method can reduce the extraction time and the use of toxic solvents, which is desirable for the extraction of bioactive compounds, as these can be incorporated into food, thus increasing the possible beneficial health effects.
AIMS
The objective of the present study was to evaluate, through experimental design, the best conditions of ultrasound-assisted extraction of the hibiscus calyx bioactive compounds, aiming its application in a food product.
MATERIAL AND METHODS
The extraction of bioactive compounds by ultrasound-assisted method was performed using a three-factor experimental design, with sonication time (X1 = 15 to 45 min), solvent-water / ethanol concentration (X2 = 0 to 50%) and temperature (X3 = 25 to 65 °C). Design Box-Behnken was used to investigate the effect of process variables on the extraction of anthocyanins and phenolic compounds, and was evaluated by surface response. The characterization of the extract obtained in the optimized condition was performed by UPLC-MS / MS and FTIR. The extracts were also evaluated during 22 days at temperatures of 4 and 25 °C, with light and without light using two 20W fluorescent lamps and a dark chamber for the parameters anthocyanins, phenolic compounds and instrumental color (CIEL * a * b * system). The pH stability (with variation of 3 to 8) was also evaluated by spectrophotometry. Two gelatin formulations with 2% and 4% addition of hibiscus extract were submitted to sensory analysis in which the evaluated attributes were: color, flavor and overall acceptance. The effects of in vitro digestion and colonic fermentation in vitro on phenolic compounds, anthocyanins and antioxidant activity (DPPH and FRAP) were evaluated in the extract and gelatin developed. All analyzes were performed in triplicate and submitted to analysis of variance and Tukey's test (p <0.05) for the least significant difference between the averages using the statistical program STATISTICA version 7.0.
RESULTS AND DISCUSSION
The ultrasound-assisted method was effective in extracting anthocyanins and phenolic compounds from hibiscus calyxes, and the final results suggest that the 45 min, 65 ° C and 25% ethanol condition can be considered the optimum region. Ultrasound extraction was more effective than the conventional method, and the relative area of the compounds identified by UPLC-MS / MS in the extract obtained by the ultrasound-assisted method are superior to the conventional method for all compounds. The compounds identified by UPLC-MS / MS in the extract were: hydroxycitric acid (m / z 207.0), caffeoylquinic acid (m / z 353.1), quercetin 3-O-glycoside (m / z 463.0), cyanidin 3-O-rutinoside (m / z 595.2), myricetin (m / z 611.0), rutin (m / z 609.3), pelargodine (m / z 272.2), cyanidin (m / z 288.3), delphinidin (m / z 303.0), delphinidin 3-O-sambubioside (m / z 598.2) and cyanidin 3-O-sambubioside (m / z 581.2), quercetin hexoside (m / z 463.0), quercetin (m / z 595.0), 4-caffeoyquinic acid. (m / z 352.0)Light and temperature factors affected the stability of the phenolic compounds and anthocyanins throughout the storage, under the different conditions studied, being that greater stability in the samples stored at 4 ºC and without light. In relation to anthocyanins and phenolic compounds, respectively, it was observed losses of only 3% and 26% in this condition, against 43% and 39% at 25 °C with light. Evaluating the color of the extract after the storage period, it was observed that for all parameters (L, a *, b * and H °) lower losses at 4 ° C and without light. In relation to pH, it was observed that the pH change affects the absorbance and color of the anthocyanins due to the ionic nature that allows changes in the structure of the molecule, mainly at alkaline pH. After studying the stability of the calyx extract of hibiscus, it was added to gelatin, in which the sample with the highest extract concentration (4%) was better accepted by the tasters with score 7 ("like moderately") in a 9-point hedonic scale for the attributes color and global acceptance. In relation to digestion and colonic fermentation in vitro the loss of phenolic compounds, anthocyanins and antioxidant activity of gelatin with addition of extract was lower when compared to the pure extract, indicating that a solid and complex food matrix is protected against alteration in pH and enzymatic action during digestion.
CONCLUSIONS
The ultrasound-assisted method was effective in extracting anthocyanins and phenolic compounds from hibiscus calyxes, being more effective when compared to conventional extraction. In general, the stability of the extracts stored at 4 °C and without light was pronounced. Regarding pH, it was observed that pH change affects the absorbance and color of the anthocyanins in function of ionic nature that allows changes in the structure of the molecule. It was observed after digestion and colonic fermentation in vitro that the loss of bioactive compounds and antioxidant activity of gelatin with addition of extract was smaller when compared with the extract, and sensorially gelatin showed good acceptance indicating that it is feasible to apply hibiscus extract in this food product.
Key words: anthocyanins, phenolic compounds, antioxidant, UPLC.

 Artigos Publicados Vinculados a Dissertação:

https://doi.org/10.1007/s13197-019-03919-y

https://doi.org/10.9755/ejfa.2020.v32.i1.2059