ANDRÉ GORDON, ROBERTA B. RODRIGUES, FRIEDHELM MARX, MENELAOS PAPAGIANNOPOULOS
University of Bonn, Institute of Nutrition and Food Sciences, Germany
A research project (PAVUC) supported by the European Union centres the development of fruit products with added values for the human health out of so far underutilized fruits from Latin America. Among others, investigations were performed on tamarillos that originate from the Andes and are increasingly offered on European fruit markets. Evaluation of the antioxidant capacity was implemented by using the GC based Total Oxidant Scavenging Capacity (TOSC) assay. This method allows the assessment of the antioxidant activity of samples against peroxyl radicals, hydroxyl radicals and peroxynitrite - three reactive oxygen species (ROS) of physiological relevance.
In total two red and one yellow variety of tamarillo were examined. Results demonstrated an intermediate antioxidant activity towards peroxyl radicals and peroxynitrite whereas the red varieties performed better than the yellow. Towards hydroxyl radicals no cultivar related differences could be constituted.
Determining the antioxidant activity of different edible parts the pericarp, the seed jelly including the kernels dominated in comparison with the fruit pulp in reference to the three different investigated ROS. However, only a small variation occurred towards hydroxyl radicals.
Ascorbic acid was identified as a potent antioxidant constituent in tamarillos. Its antioxidant efficiency is good against peroxyl radicals. Towards peroxynitrite ascorbic acid demonstrates a moderate antioxidant behaviour. No activity in relevant concentrations was exhibited towards hydroxyl radicals. Amounts of ascorbic acid were 4.5 fold higher in the seed jelly rather than the fruit pulp. Compared to oranges, tamarillo fruit contains a similar amount of ascorbic acid (between 25--30 mg/100 g fresh weight of the edible part) but shows a pronounced higher TOSC value against peroxyl radicals which may be explained by the presence of anthocyanins. The seed jelly contains in total eight anthocyanins which are derived from the aglycons cyanidin, delphinidin, and pelargonidin. A pelargononidin-hexosyl"=desoxyhexoside and a cyanidin"=hexosyl"=desoxyhexoside dominate quantitatively within the seed jelly. Furthermore a variety depending difference concerning the anthocyanin pattern was revealed.
Anthocyanins were proven to be good antioxidants against peroxyl radicals but not against peroxynitrite and hydroxyl radicals. The measured activity against the both latter suggests that maybe other compounds take part in antioxidant reactions.
Keywords: Antioxidant capacity, hydroxyl, peroxyl, peroxynitrite, tamarillo, TOSC