Phenolic compounds and in vitro antioxidant activity of six accessions of mashua (Tropaeolum tuberosum r. & p.) from puno region, Peru

Mashua (Tropaeolum tuberosum R. & P.) is an Andean crop of high nutritional value and medicinal properties, which presents a great diversity in morphology and color. The aim of the study was to evaluate the content of phenolic compounds and in vitro antioxidant activity of the most economically important mashua accessions in the Puno Region, Peru. Six accessions of mashua (three purple-colored and three yellow-colored) were evaluated. The content of total polyphenols, total flavonoids and identification of phenolic compounds was determined by the Folin-Ciocalteu assay, aluminum chloride colorimetric method and HPLC-DAD, respectively. In vitro antioxidant activity was evaluated using the FRAP and DPPH assays. In general, the purple-colored mashua had a significantly higher content of total polyphenols, total flavonoids, and in vitro antioxidant activity compared to the yellow-colored mashua; being the Tt-23 accession purple-colored (peel/pulp, purple/purple), which presented a significantly higher content of phenolic compounds and in vitro antioxidant activity compared to the other accessions evaluated (P<0.05). Furthermore, a significant correlation was observed between FRAP and DPPH activities with the total content of polyphenols and flavonoids (P<0.01), as well as between FRAP activity and the caffeic acid and rutin levels (P<0.05). These results suggest that purple-colored mashua, particularly the Tt-23 accession (peel/pulp, purple/purple), has better nutraceutical and antioxidant properties due to its higher content of phenolic compounds.