Chemical profile and antioxidant capacity verification of Psidium guajava (Myrtaceae) fruits at different stages of maturation.

Psidium guajava (Myrtaceae), a common plant in Cariri region, Ceara, Brazil, as well as in various parts of the world, contains high concentrations of bioactive compounds and in many communities its parts are used for therapeutic purposes. Studies describe antioxidant, antimicrobial and anti-diarrheal actions from extracts obtained from leaves, but information about the activities of the fruits and comparison of these at different maturity stages (immature, partially mature and mature) are scarce. This study aims to evaluate the antioxidant properties by quantifying the levels of phenolic and flavonoid compounds, carotenoids and vitamin C of P. guajava fruits at different stages of maturation. The content of phenolic compounds for the immature fruit, partially mature and mature were: 22.41; 34.61 and 32.92 mg of AG/g fraction. The flavonoid content for immature fruits, intermediate and mature were: 2.83; 5.10 and 5.65 mg RUT/g fraction, respectively. Following the same standards of maturation stages, the ascorbic acid content was determined with values of 0.48; 0.38 and 0.21 mg AA/g fraction, respectively. HPLC analysis identified and quantified the presence of gallic acid, catechin, chlorogenic acid, caffeic acid, epicatechin, rutin, quercitrin, isoquercitrin, quercetin, kaempferol, glycosylated campeferol, tocopherol, β-carotene and lycopene. The antioxidant activity carried out by DPPH method showed the mature fruits bearing the best results, whereas chelation of Fe2+ ions showed higher percentage for the immature fruit. The results obtained by lipidic peroxidation were not satisfactory.