Fluctuation of isoflavone concentration in soybean varieties under conventional and organic farming

Polyphenols have a wide range of secondary metabolic compounds, which enter several fundamental processes in plant physiology. Some polyphenols, such as lignins, flavonoids, and others, have good effects on human health. Soybean is unique among the legumes, in that it is a concentrated source of isoflavones. Soybean contains three major isoflavone aglycones (i.e., daidzein, genistein, glycitein) and their corresponding glucosides, malonyl-esters and acetyls (Jackson et al., 2002). Ingestion of isoflavones is associated with many health benefits (Sarkar and Li, 2004). Soybean seed is made up of a large embryo containing two primary organ systems - germ and cotyledons - surrounded by a seed coat of maternal origin, and their isoflavone accumulation varies in both quantity and type. During maturation, the embryonic cells synthesize proteins and secondary metabolites, among which are isoflavones. The latter are considered natural active compounds in plant defence, produced against unfavourable conditions, and their amount is expected to vary with agronomic management. Until now, as regards isoflavone production, the effects of organic farming and low input have not been clearly recognised in soybean. In this framework, the aim of this research was to evaluate the influence of the environment, agricultural management (conventional vs. organic) and choice of variety on soybean isoflavone production in the seed sites.