Antioxidant Activity of An Italian Heirloom White Fleshed Sweet Potato

Sweet potato (Ipomoea batatas L.), one of the most cultivated vegetables worldwide, is well known and studied especially for genotypes with colored flesh. In Italy this crop is a niche crop mainly grown in the North. As a consequence in Italy it has never been considered as a staple crop but recently the interest began to increase even though little is known about both growing techniques and its nutritional features. Moreover some researches indicated that leaves and vines are particularly rich in antioxidant compounds and that can be considered a good and cheap source for extraction industry. The aim of this study was to quantify and characterize the antioxidant activity of 2 heirloom sweet potato, grown in North Italy characterized by different leaf shape (heart-shaped (HS) and lobed (LS)). Heirloom plants were grown in contiguous plot using same techniques by a farmer in Anguillara Veneta – Padova – Italy (45° 13’N – 11° 88’E) in 2008. Biomass collected during the growing cycle and at commercial harvest (11^th and 26^th of August and 22^nd of September) was analyzed at the Department of Environmental Agronomy and Crop Science of the University of Padova within 48 hr from sampling. During growing cycle leaf blade, petiole/vine, stem and roots (not yet, partially (up to 100 g) and completely (more than 100 g) swollen) were analyzed to determine total antioxidant activity (AOA), total phenols (TP) and vitamin C (VC) content. At harvest only roots were considered after grouping in four caliber classes (0-100, 100-200, 200-400 e > 400 g). Results showed, on average, that HS biomass had higher AOA, TP and VC than LS with no differences among sampling times with the exception of VC whose content in the first sampling data was lower than in the others. Within the plants AOA and TP where higher in leaves blade followed by stem, petiole/vine, small, medium and fully enlarged roots. VC content showed an opposite trend than AOA and TP. Weight classes did not show any difference in term of AOA, TP and VC in both lines even though a late harvest (8 day of delay) induced a reduction of VC content in all the groups. As a conclusion it is possible to state that, nevertheless its lower content of antioxidant compounds as compared with the colored flesh, also the less studied white fleshed potato could be considered an healthy functional food.