Isoflavonoids chemical structure

FIGURE 7.2 Chemical structures of the main soy (genistein and daidzein) and red clover (biochanin A and formononetin) isoflavonoids (aglycones and glucosides). 

It is concluded that the sensitivities of the MDR- and MRP-mediated drug resistance mechanisms by the inhibitory flavonoids and isoflavonoids might differ because of selective activity based on their chemical structures this is in good agreement with other studies. 

The extracts of a famous Chinese herbal medicine, the heartwood of Dalbergia odorifera displayed potent repellent activity toward A. cochlioides zoospores. Three isoflavonoids were isolated as the active factors from the extract by a series of column chromatography followed by preparative TLC [36,82], Their chemical structures were assigned on the basis of physicochemical data including 2D NMR. 

Overexpression of P-glycoprotein associated with multidrug resistance represents a serious problem in cancer treatment. Evaluation of catechins, fla-vonoids, isoflavonoids, and anthocyanins effects on multidrug-resistant human epidermal carcinoma cells has demonstrated that catechins and antho-cyanidins are most effective inhibitors of P-gp overexpression. It was observed that hydrophobicity enhances planar flavonoids inhibitory effects without affecting nonplanar flavanols activity that significantly depended on their chemical structure [119]. 

More chemistry has been carried out on the heartwood flavonoids of the Leguminosae than on those of any other plant family. This is not surprising considering that there are many tree species in what is a very large family and also that these trees are used as timber, for furniture, or as a source of tannin. But it also reflects the fact that there are an enormous variety of chemical structures present, particularly of isoflavonoids. The discovery of interesting and novel structures in one tree inevitably encourages investigation of related species for further novelties. 

Figure 8.2 Numbering of the C6-C3-C6 flavonoid skeleton and the chemical structures of the main subclasses of flavonoids and isoflavonoids present in the diet.

Ito, C. et al., Chemical constituents of Millettia taiwaniana structure elucidation of five new isoflavonoids and their cancer chemopreventive activity. Journal of Natural Products, 67, 1125, 2004. 

Tamura, S., Chang, C., Suzuki, A., Kymai, S. Chemical studies on clover sickness. I Isolation and structural elucidation of two new isoflavonoids in red clover. Agri Biol Chem 1969 33 391-397. 

Isoflavonoids are a characteristic and very important subclass of flavonoids. Their structures are based on the 3-phenylchromen skeleton that is chemically derived from the 2-phenylchromen skeleton, by an aryl-migration mechanism. Structurally, isoflavonoids can be classified according to the oxidation of the C15 skeleton, their complexity and the internal formation of heterocyclic rings [6],... 

Phytoalexins are low molecular weight products which are produced in response to elicitors such as microbial, herbivorous or environmental stimuli (Poulev et al. 2003). Once plants detect a pathogen signal, a complex mixture of secondary metabolites is produced to control the invader. These molecules are synthesized de novo, and thus involve the activation of certain genes and enzymes required for their synthesis (Kuc 1995). Phytoalexins are chemically diverse and may include many chemical classes such as simple phenylpropanoid derivatives, alkaloids, gly-costeroids, flavonoids, isoflavonoids, various sulphur products, terpenes and polyketides (Hammerschmidt 1999). There is no boundary between phytoalexins and phytoanticipins, and in one plant species a certain chemical can function as a phytoalexin, whereas it has the function of a phytoanticipin in another species (Junghanns et al. 1998). It is important to point out that the distinction between phytoanticipins and phytoalexins is not based on their chenucal structure but rather on how they are produced. Thus, the same chemical may serve as both phytoalexin and phytoanticipin, even in the same plant (VanEtten et al. 1994). 

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