Influence of ripening stage on bioactive compounds and antioxidant activity in nine fig (Ficus carica L.) varieties grown in Extremadura, Spain

The aim of this study was to characterise nine commercial fig (Ficus carica L.) varieties differing in colour (dark-purple, brown, green, and yellow-green) at three different ripening stages in regards to the health-promoting compounds of their fruits and to identify and quantify the bioactive compounds as well as total antioxidant activity (TAA) in the skin and flesh of each variety. Significant differences (p < 0.05) were found between varieties and ripening stages. Dark-coloured varieties showed the highest levels of total phenolic compounds (from 26.7 to 169.5 mg gallic acid equivalents/100 g), quercetin-3-O-rutinoside (between 4.6 and 11.9 mg/100 g), and anthocyanins, specially cyanidin-3-O-rutinoside (from 3.03 to 97.4 mg/100 g), while brown-, green-, and yellow-green-coloured varieties contained the highest levels of chlorogenic acid (between 0.7 and 2.1 mg/100 g), total Vitamin C (from 0.8 to 9.0 mg/100 g), and (+)-catechin as proanthocyanin cleavage products (from 3.1 to 17.3 mg/100 g). Levels of TAA were measured by 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) total radical scavenging capacity both in hydrophilic (H-TAA) and lipophilic (L-TAA) fractions. The darker varieties exhibited higher H-TAA values, ranging from 16.3 to 177.4 mmol Trolox equivalents/100 g, than the lighter ones. In the case of L-TAA, its concentration also depended directly on the genotype and less on the ripening stage. We found higher concentrations of bioactive compounds and a higher antioxidant capacity in the skin compared to the flesh; moreover, their content increased during the ripening process, reaching the maximum level of phenolic compounds at stage three, although these changes were deeper in the dark-coloured varieties and in the brown-coloured variety 'San Antonio' Based on our results, it is advisable to consume unpeeled, fully ripe, dark figs in order to optimally benefit from the health-promoting properties.