Abordagem quimiométrica e avaliação físico-química, bioativa e biológica in vitro da acerola (Malpighia emarginata) in natura e liofilizada

Abstract

Brazil is an important producer of tropical fruits. Among them, acerola (Malpighia emarginata) is recognized for its high content of ascorbic acid (AA), total phenolic compounds (TPC), carotenoids, anthocyanins and potent antioxidant capacity. Considering the bioactive and commercial value of this fruit, the present work aimed to evaluate acerola using different approaches, which are presented in the six chapters of this thesis. A general introduction opens this document and discusses keytopics covered throughout the research. The second chapter shows the evaluation of the whole acerola fruit in regard to its concentration of bioactive compounds (AA, TPC) and antioxidant activity (DPPH), by the near infrared (NIR) technique and application of chemometric analysis. In the third chapter, freeze-drying was applied to acerola pulp and acerola pomace in order to compare the final products to the fresh fruit, as well as to monitor the stability of the acerola powders along the storage. In the fourth chapter, commercially purchased freeze-died acerola was evaluated and compared to selected freeze-dried fruits (camu-camu, apple and pineapple) in regard to in vitro biological analyzes. Selected phytochemical compounds (AA, TPC, anthocyanins, phenolic acids) and antioxidant activity (by two methods of detection: reducing iron potential - FRAP and capturing the radicals of 2,2 - diphenyl - 1 - picrylhydrazyl - DPPH) of the fruit extracts were analyzed. In addition, the effects of these extracts on reducing the production of reactive oxygen species (ROS) and nitric oxide (NO) in RAW 264.7 macrophages were investigated. Initially, the toxicity of the samples (reduction method of 3- (4,5- dimethylthiazol-2yl) -2,5-diphenyl tetrazolium bromide - MTT) to RAW 264.7 cells was assessed. The anti-inflammatory activity of acerola extracts was tested by analysing enzymes and mediators with proinflammatory activity (inducible nitric oxide synthase - iNOS, cyclooxygenase – COX-2, interleukins - IL1β and IL-6, tumor necrosis factor - TNFα), in addition to an in vitro assay to investigate the cell migration properties of freeze-dried extracts in adult human dermal fibroblast cells (HDFα). The final chapters 5 and 6 show the conclusion and the literature sources used hrere. The results show that the NIRS model is a fast and reliable non-destructive analytical strategy to evaluate the ascorbic acid, however did not show good settings to the phenolic and antioxidant capacity in acerola fruits. It has also been demonstrated that freeze-dried acerola powders retain high ascorbic acid concentration and the preservation of ascorbic acid and anthocyanins is more effective under refrigerated storage. The results of the in vitro biological tests showed that acerola extracts, camu-camu, apple and pineapple are able to reduce the production of reactive oxygen species (ROS). Only freeze-dried acerola and camu-camu extracts reduced the production of reactive nitrogen species (NO). Extracts of these fruits also suppressed the expression of IL1β and IL6, and freeze-dried acerola is the only one capable of reducing the expression of COX-2 enzyme. The acerola was also able to enhance cell migration, based on the in vitro results obtained in HDFa cells, which reflects the skin cells' ability to regenerate after injury. The high ascorbic acid content in acerola seems to play an important role in the observed in vitro biological effects. Overall, it is concluded that acerola presents relevant bioactive and in vitro biological potential, which can justify its exploitation as a functional ingredient in food and pharmaceutical formulations.