isoflavonoid

Isoflavonoids are a subclass of flavonoids, a group of plant secondary metabolites. Their defining feature is a 3-phenylchromen-4-one skeleton, in which the B ring is attached to the heterocycle at carbon 3. This structural arrangement distinguishes isoflavonoids from other flavonoids, where the B ring is linked differently. The principal aglycone isoflavones include genistein, daidzein, and glycitein; many glycoside derivatives occur in edible plants.

Occurrence and biosynthesis

Isoflavonoids are especially abundant in legumes, with soybeans (Glycine max) being a major dietary source. They also occur in red clover, chickpeas, and other legumes. In plants, isoflavonoids participate in defense responses and symbiotic interactions, and their production can be modulated by environmental factors. In animals and humans, dietary isoflavonoids are typically consumed as glycosides and are hydrolyzed by gut microbiota to aglycones, which are then absorbed and metabolized in the liver.

Biological activity

Isoflavonoids function as phytoestrogens, compounds that can weakly bind estrogen receptors, particularly ERβ. They also exhibit antioxidant and anti-inflammatory activities and can influence various signaling pathways. In humans, these activities have prompted research into potential roles in disease risk modification, including hormone-related cancers, cardiovascular health, and bone health; results are heterogeneous and dose- and context-dependent.

Dietary sources and safety

Beyond soy, isoflavonoids occur in smaller amounts in other legumes and plant foods. Typical dietary intakes are generally considered safe, though high-dose supplements may carry risks or interact with thyroid function in iodine-deficient individuals. As with many bioactive plant compounds, effects can vary based on individual gut microbiota composition and metabolism.

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