Antioxidants in Bolivian Plant Foods. Antioxidant Capacity, Flavonoids and other Phenolic Compounds

Abstract: The total antioxidant capacity was measured and the major phenolic and flavonoid compounds were identified and quantified in a selection of Bolivian crops growing at different altitudes above seal level (a.s.l.). Spectrophotometric methods and high-performance liquid chromatography (HPLC) were used for the study of Andean cereals, tubers, berries, fruits and vegetables. The total antioxidant capacity (TAC) was measured with the ABTS method (2,2'-azino bis(3-ethylbenzthiazoline-6-sulphonic acid) and the FRAP method (ferric reduction antioxidant power). Total flavonoids (TF) were measured by flavonoid-aluminium complex formation and total phenols (TPH) by the Folin & Ciocalteu method. Individual phenolic compounds were analysed by reversed-phase HPLC. Canihua (Chenopodium pallidicaule), an Andean grain collected at an altitude of about 3850 m a.s.l., showed the presence of eight major compounds, identified as catechin gallate, catechin, vanillic acid, kaempferol, ferulic acid, quercetin, resorcinol and 4-methylresorcinol. In wild strawberries (Fragaria vesca) growing at high altitude the TAC showed somewhat higher values of antioxidants than in cultivated strawberries, and the amount of ellagic acid was also higher than in cultivated strawberries. The results obtained in the tubers oca (Oxalis tuberosa) and ulluco (Ullucus tuberosus), the most widely grown and economically important root crops of the Andean region, showed that they can be considered as important sources of antioxidants in the Andean diet. For instance, anthocyanidins and flavonoids were found in these foods. TAC, TPH, TF and the contents of individual phenolic compounds were also assessed in potato cultivars (Solanum sp.) before, during and after the traditional freeze- and sun-drying of potato, to produce chuño. The results indicated that the chuño process resulted in only a slight loss of antioxidants and phenolic compounds. In total, 102 samples were analysed using the four spectrophotometric methods mentioned above. Based on the results, it can be concluded that many Andean foods are good sources of antioxidants.