ORIGINAL PAPER Comparisons of phenolic compounds, isoflavones, antioxidant capacity and oxidative enzymes in yellow and black soybeans seed coat and dehulled bean Slad¯anaZ ˇ ilic ´ • H. Gu ¨l Akıllıog ˘lu • Arda Serpen • Vesna Peric ´ • Vural Go ¨kmen Received: 9 February 2013 / Revised: 16 April 2013 / Accepted: 22 April 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract The total and individual phenolic profiles and their contribution to antioxidant capacities of seed coats and dehulled beans of black and yellow soybeans were investigated. In addition, lipoxygenase (LOX) and peroxi- dase (POD) activities were also determined. Black seed coats had the highest content of total phenols, flavonoids and anthocyanins, in addition the highest catechin and protocatechin contents. On the other hand, dehulled beans from yellow soybeans had the highest levels of ferulic and p-coumaric acid content, and free and bound isoflavone content. The LOX activity was concentrated in the de- hulled beans of both black and yellow soybeans, while a high POD activity that can be attributed to a dominant gene EpEp was presented in seed coats of yellow soybean genotype Galeb. Due to the high concentration of phenols, the black seed coats from soybean genotypes Black Tokio and Cornaja had the highest ABTS Á? -scavenging capacity (597.46 and 486.15 mmol Trolox Eq./kg d.m., respec- tively). The results suggest that the black seed coat as well as dehulled bean from yellow soybeans would potentially provide sources of natural antioxidants that may play a crucial role in human health protection. Keywords Antioxidant capacity Á Isoflavones Á Oxidative enzymes Á Phenolic profiles Á Soybean Introduction Soybean has been regarded as a nutritionally rich food ingredient. Recently, attention has been given to the signifi- cant potential of soybean in the prevention of diseases such as atherosclerosis, coronary heart disease and cancer [1, 2]. Given that oxidative damage represents one of the mecha- nisms leading to chronic diseases, many researches have been focused on the antioxidant compounds in soybeans. A form of flavonoid in soybean, isoflavones, has been found to be sec- ondary important compounds with many chemical actions. Soybean and its processed products are the main source of isoflavones in the human diet. The three isoflavone aglycones, namely genistein, daidzein, and glycitein, are each present in four chemical forms in soybeans and soya foods. However, the isoflavones occur primarily in their storage form as mal- onyl glucosides, whereas significant level of glucosides and low level of aglycones and acetyl glucosides are present [3]. Isoflavones are structurally similar to naturally occurring estrogens and show promise in protecting against hormone- dependent cancers [4]. Increasing evidence, especially in light of results from recent human studies, tends to support the beneficial effects of soybean isoflavones in the prevention of bone loss in postmenopausal women [5]. While the con- sumption of soya food has been frequently associated with beneficial health effects, the potentially adverse effects of isoflavones are likely underappreciated. The general human population is continuously exposed to various kinds of endocrine-disrupting chemicals (EDCs). The ability of iso- flavones to bind and activate estrogen receptors (ERs) fits well within the definition of EDCs, which states that these S. Z ˇ ilic ´ Á V. Peric ´ Department of Technology and Breeding Department, Maize Research Institute, Slobodana Bajic ´a 1, Belgrade-Zemun, Serbia H. G. Akıllıog ˘lu Á V. Go ¨kmen (&) Department of Food Engineering, Hacettepe University, 06800 Beytepe, Ankara, Turkey e-mail: vgokmen@hacettepe.edu.tr A. Serpen Á V. Go ¨kmen Food Research Center, Hacettepe University, 06800 Beytepe, Ankara, Turkey 123 Eur Food Res Technol DOI 10.1007/s00217-013-2005-y