Avaliação do perfil eletroquímico e fitoquímico de extrato de pitangas

Abstract

Pitanga (Eugenia uniflora) and pitangatuba (Eugenia selloi) belong to the Myrtaceae family, are native to Brazil and are considered superfruits due to their high nutritional value. The pitanga is available in a variety of colours, from red (the most popular) to black (purple) and yellow (less common). The pitangatuba has a bright yellow colour and an intense bittersweet flavour. Apart from the difference in pigmentation, the chemical richness in bioactive constituents of medicinal interest of each fruit is still an under-explored area. Both species have remarkable therapeutic properties, mainly due to their ability to inhibit free radicals. Therefore, due to the importance of determining the antioxidant capacity in relation to the therapeutic effect of these fruits, this study aimed to evaluate the antioxidant potential of the pitanga and pitangatuba varieties by electrochemical methods, as well as to verify the vasorelaxant activity and correlate these results with the phenolic composition determined by mass spectrometry. For the electrochemical experiments, the electroanalytical methods used were differential pulse voltammetry and square wave voltammetry. Additionally, a biosensor in carbon paste electrode using the enzyme polyphenoloxidase, obtained from the branches of the Cordia superba plant, was applied to the selected extracts. The vasorelaxant activity of the Eugenia uniflora varieties (red and purple) was evaluated in aortic artery rings of male Wistar rats, using arteries with intact vascular endothelium. The endothelial nitric oxide synthase (eNOS) pathway and the inhibitor N-nitro-L-arginine-methyl-ester (L-NAME) were used in this analysis. In the electrochemical tests, a similar profile was observed, with anodic peak c.a. Epa1 = 0.26 V for red and purple pitangas and 0.18 a 0,26 V for pitangatuba, which are indicative of polyphenolic compounds with high antioxidant potential. The extracts applied to the biosensor demonstrated significant improvement in the electroanalytical signal of red and purple Eugenia uniflora and Eugenia selloi when compared to the electrode without modification. The phenolic composition of Eugenia fruits determined by mass spectrometry revealed the predominance of cyanidin 3-O-glucoside in purple pitanga, myricetin 3-Ohexoside, apigenin and delphinidin 3-O-glucoside in red pitanga and gallic acid in pitangatuba. Pharmacological tests showed that Eugenia uniflora presented induction of nitric oxide production by endothelial cells and reduction of oxidative damage caused by KCl. On the other hand, purple pitanga presented better antioxidant capacity, corroborating the results obtained in other studies, highlighting its importance as a functional food.