Total phenolic compounds and antioxidant capacities of major fruits from Ecuador

Abstract

Seventeen fruits from Ecuador were analysed for total soluble phenolic compounds content and for antioxidant capacity, using three different methods (DPPH, FRAP and ABTS⁺). For the total phenolic content measured by the Folin–Ciocalteu method, three groups, having <100, 200–500 and >1000 mg GAE/100 g FW, were clearly distinguishable. Andean blackberry, capulí cherry peel and banana passion fruit were classified in the third group, with concentrations of 2167, 1494 and 1010 mg of GAE/100 g FW, respectively. Antioxidant capacity analyses revealed the same classes. FRAP and ABTS⁺ gave comparable results and were highly correlated (y = 0.691x + 6.78; r² = 0.908). Spectrophotometric measurements showed that the Andean blackberry and capulí peel but not banana passion fruit contained high levels of anthocyanins (λ_max = 520 nm).

Introduction

In addition to their delicious taste and refreshing flavour and aroma, fruits add important vitamins, minerals and other bioactive compounds to the human diet. It has been shown in epidemiological studies that a correlation exists between the consumption of fruits and reduced risk of chronic diseases (Block et al., 1992, Chun and Kim, 2004, He et al., 2007, Kuskoski et al., 2005, Van’t Veer et al., 2000, Wu et al., 2004). The combination of vitamins, minerals, phenolic antioxidants and fibre seem to be responsible for these effects (Ruxton, Gardner, & Walker, 2006). Parallel with this recognition, the consumption of tropical or “exotic” fruits has increased all over the world.

Different fruits differ markedly in the quantity and types of phenolic antioxidants and their conjugates (Macheix, Fleuriet, & Billot, 1990). The use of simple “total antioxidant capacity” methods differing in their way of generating free radicals, the strategy to measure the end point of the inhibition reaction, and the sensitivity towards the different reducing molecules in the sample (Pellegrini et al., 2003, Roginsky and Lissi, 2005). Therefore, more than one method should be used to gain useful information about the total antioxidant capacity of phenolic compounds.

Similar to other tropical countries, Ecuador is rich in a wide range of delicious fruits that are reaching international markets. This work is a first step to measure the total phenolic content in fruits from Ecuador using the Folin–Ciocalteu reagent and three total antioxidant activity methods.