Isoflavones are a relatively small, structurally well defined, group of plant
secondary metabolites (natural products), which are of particular interest as
biologically active, non-nutrient constituents of animal feed and human food.
Chronologically, they were noticed at the beginning of XIXth century phytochemical
studies as a class of plant pigments of considerable practical importance, but gained
more significance after discovery of their estrogenic activity and interference with
hormonal homeostasis of sheep, during 1940s. Contemporary studies of isoflavones are
inseparably connected with soy, which is not only one of the principal agricultural
crops of global significance, but also the richest source of genistein, daidzein and
glycitein, which can occur as glycosides, aglycones or partly acylated glycosides. The
presence of isoflavones in food products, which are derived from processing of
soybean are generally considerd safe and beneficial for human health. Relatively
recently, sufficiently selective and accurate analytical methods have been developed.
These techniques have enabled the study of metabolic fates of isoflavones in
experimental animals, as well as human patients, at the nanomolar levels which result
from soy products ingestion or administration of pure isoflavones preparations.
Although isoflavones share many physicochemical and biochemical characteristics
with more numerous groups of natural products: flavonoids and polyphenolics (which
are recognized as antioxidants, scavengers of the reactive oxygen species and antiinflammatory
agents), they also feature some selective activities, like estrogenicity or
multitarget and pluripotent anticancer action. The large amount of isoflavone
pharmacological data accumulated tend to become less consistent as we advance from
molecular level, through animal models, to human clinical trials, which indicates
shortcomings of traditional approaches and the need for including systems biology
methods and interpretations. Natural isoflavones remain interesting molecular probes,
and lead compounds for several therapeutic directions; their presence in certain food
products and variety of dietary supplements seems to be generally accepted, but it
becomes evident that prospective drug development must take into account
considerable differences in individual metabolism, which results in large part from very
different microbiota which harbors in human intestines. On the other hand, synthetic
chemistry of phenylpropanoids in general, and isoflavones in particular, is well
developed and capable of delivering modified structures in both: form of structurally diverse dedicated libraries, and also in form of a scalable process for manufacturing of
an active pharmaceutical ingredient featuring selected structure.
Keywords: Isoflavones, secondary metabolites, natural products, plant
polyphenolics, flavonoids, isoflavone biosynthesis, isoflavone metabolism, soy
isoflavones, phytoestrogens, genistein, daidzein, equol, puerarin, isoflavone
glycosides, synthesis of isoflavones.
