Caracterização de frutos nativos da região amazônica e desenvolvimento de um biossensor amperométrico para determinação da capacidade antioxidante

Abstract

Fruit consumption has been encouraged not only by providing essential nutrients to the human body, but by being natural sources in bioactive compounds that promote health benefits and reduce the risk of developing chronic non-communicable diseases. Considering that the Brazilian Amazon has an immense fruitful diversity, but little information on its nutritional, antioxidant and bioactive properties, this work had the objective to characterize ten native fruits of the Amazon region. The characterization was initially by conventional bromatological analyzes, followed by the determination of the minerals Ca, Cu, Fe, Li, Mg, Mn, Na and Zn by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES). Afterward the antioxidant capacity of the fruits was evaluated using different colorimetric methods (DPPH, ABTS, and NBT), the evaluation of the antiproliferative activity against the human colon cancer cell line (caco-2), the determination of bioactive compounds (vitamin C and total phenolic compounds), and the characterization of the profile in phenolic compounds, using Ultra High Performance Liquid Chromatography (UHPLC) coupled to high resolution mass spectrometry. Considering the disadvantages of conventional methods for the determination of antioxidant capacity, this study aimed to develop an amperometric biosensor using as a transducer a conventional system of three screen printed electrodes on PVC, containing prussian blue (PB) as electrochemical mediator. In view of this, the conditions of biofunctionalisation of the xanthine oxidase enzyme (XOD) with respect to the XOD: PVA-AWP ratio, the irradiation time under the neon light and the amount of XOD used in each sensor were optimized. Afterwards, the analytical performance of the biosensor was evaluated, and the antioxidant capacity of a pure standard substance and fruit extracts was finally detected. The results of the bromatological characterization evidenced higher lipid, protein and energy contents in buriti, monguba and uxi samples. The samples of abiu, açaí, bacuri, buriti, inajá, monguba, pajurá and uxi were shown with high content and/or source in one or more minerals. In the pulps of biribá and bacuri, a high lipophilic antioxidant capacity was observed against different free radicals, whereas the fruits of abiu, inajá and monguba presented higher hydrophilic antioxidant capacity. The antiproliferative activity of the fruits of biribá, inajá, monguba and pajurá led to a significant inhibition in the cell growth of caco-2. The majority of the pulps were food of high vitamin C content, while the fruits biribá and pajurá were classified as sources. Higher concentrations of hydrophobic phenolic compounds were observed in the bacuri pulp, whereas in the abiu, bacuri, inajá and monguba samples, higher hydrophilic phenolic contents were verified. Analyzing the chromatographic composition of the extracts of biribá, inajá and monguba, it was possible to quantify a total of 11, 25 and 21 phenolic compounds, respectively, with important biological activities. The results provide information that may contribute to better understanding the Amazon biodiversity as well as the development of biotechnology for the conservation of the Amazon biome. As regards the developed biosensor, the optimized operating conditions were: XOD: PVA-AWP of 1: 2; time of exposure to the neon light of 30 min, and enzymatic loading of 8 mU per electrode. The biosensor was stable, with fast responses, easy automation, relatively low cost, high sensitivity, low detection and quantification limits. The applicability of the biosensor was demonstrated by the in vitro analysis of gallic acid, taken as standard antioxidant, as well as of Amazonian and non-autochthonous fruits.