Antioxidant Activity of Elite Large-Seeded Soybean Breeding Lines in Vriginia.

abstract

Antioxidants have been reported to reduce the risk of human diseases caused by free radical-induced oxidative damage such as cardiovascular diseases, diabetes and cancer. Soybean seeds have been shown to be the source of natural antioxidants in order to provide health advantages and therapeutic properties. The most popular soyfood, soy milk and tofu, requires large-seed soybeans. However, the information of antioxidant capacity of large-seeded soybeans is very limited. Eight elite large-seeded (> 20 g/ 100 seeds) soybean breeding lines developed by Virginia State University were investigated in 2006 and 2007 for seed size, yield and antioxidant activity shown by total phenolic content (TPC), radical scavenging activities against free 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and oxygen radical absorbance capacity (ORAC). Seed size of all lines in 2006 was 26.0 g/ 100 seeds in average, larger than that in 2007 (21.3 g/ 100 seeds) due to better precipitation in 2006. The yield of most tested lines was not significantly different in 2006 and 2007 except for the largest breeding line VS03-688 because of its poor stands in 2007. The TPC value of all breeding lines ranged from 5.6 (VS03-709) to 9.8 (VS03-688) mg GAE/ g without significant difference. The average TPC value in 2006 was 5.4 mg GAE/ g, significantly lower than that in 2007 (8.2 mg GAE/ g). The black soybean had highest TPC of 8.6 mg GAE/ g followed by brown soybeans of 6.8 mg GAE/ g, and the yellow and yellow/brown soybeans had the lowest TPC of 5.9 mg GAE/ g, but TPC of different color beans were not significantly different. There were significant differences in free radical scavenging activities among soybean breeding lines (P < 0.05). VS03-620 and VS03-709 had higher DPPH of 121.0 and 82.4 uM TE/g, respectively, than other breeding lines. DPPH between years were almost the same. The yellow soybeans had significantly higher DPPH of 101.7 uM TE/g than yellow/brown (10.8 uM TE/g), brown (10.1 uM TE/g) and black soybeans (4.3 uM TE/g).  ORAC was not affected by all variables because ORAC was not different among all breeding lines, between years, or among different color beans. Seed size, yield, TPC, DPPH and ORAC were not significantly correlated, but most pairs showed negative correlation except for seed size and ORAC as well as yield and ORAC. VS03-688 with largest seed size of 29.3 g/ 100 seeds, unique black seed coat, very competitive yield and high antioxidant activity is a potential soyfood source of antioxidants for positive health benefits and also a superior germplasm for large-seeded soybean breeding program.