Resumo

NAVIA, Alejandra et al. Determination of the phenolic contents and evaluation of the Antityrosinase activity, and the antioxidant indexes of four Bolivian Quinoa varieties    . Rev. Bol. Quim [online]. 2020, vol.37, n.1, pp.12-20. ISSN 0250-5460.

Abstract Four varieties of Bolivian quinoa (QJG Quinoa Jacha Grano, QRB Quinoa Real Blanca, QRN Quinoa Real Negra and QRR Quinoa Real Roja) have been studied in order to valorize them through the establishment of the phenolic contents and consequently by their antioxidant indexes. In addition, and in this pathway, the antityrosinase activity of the four varieties was measured. One important quinoa-endemic glycosylated flavonoid, mauritianin 1 (Kaempferol-3-O-(2,6-di-O-α-ramnopyranosyl-β-galactopyranoside) was isolated, and identified by cromatographic and spectroscopic methods and it was quantified. The four quinoa samples were treated by means of solid-liquid extractions with hydro-alcoholic 8:2 solvents. Quantifications and evaluations were done in the samples of the four varieties of quinoa and in phenolic rich fractions from the extract of QJG, and in compound 1, coming from the QJG extract. In a series of in vitro tests, antioxidant indexes, by means of the total phenolic content and ABTS methods,  and antityrosinase activities, by using the fungal tyrosinase method,  of phenolic rich fractions and of the pure compound 1 were evaluated, 1 showed an important antityrosinase activity (74.73% I at 1.67 mg/mL) and antioxidant (826.68 mg GAE/g and 1141.38 µM Trolox/g), as well as the phenolic rich fraction from the extract of QJG named as EEW-1 that showed 69.89% I of the enzyme tyrosinase and significant antioxidant activity (246.08 mg GAE/g and 569.21 uM trolox/g), suggesting that these products could have a potential application in dermatology, cosmetics and food processing.

Palavras-chave : Quinoa; Chenopodium quinoa; Antityrosinase; Antioxidant; Total Phenolic Contents; Mauritianin.

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