Chlorination, isoflavones

D Alessandro T, Prasain J, Benton MR et al. Polyphenols, inflammatory response, and cancer prevention chlorination of isoflavones by human neutrophils. J. Nutr. 133, 3773S-3777S, 2003. Boersma BJ, D Alessandro T, Benton MR et al. Neutrophil myeloperoxidase chlorinates and nitrates soy isoflavones and enhances their antioxidant properties. Free Radical Biol. Med. 35, 1417-1430, 2003. 

It was shown later that the streptomycete can only modify rather than biosynthesize these compounds [66] and that all such derivatives, i.e. even genisteins (64,65) come from the soy meal or cotton seed and are not produced by streptomycetes. These results demonstrate clearly that flavonoids isolated from streptomycetes cultivated on media containing plant components, such as soy meal or cotton seed, always come from the cultivation medium and are not of microbial origin. The same effect was observed in S. griseus [65] producing two additional chlorinated genisteins (66,67). This also holds true [67] for isoflavone (68) isolated from Japanese soil. 

Figure 4.5 Sites of tissue modification of isoflavones. In the A-ring, chlorination and hydroxy-lation occur at the 6- and 8-positions. In the B-ring, hydroxylation and nitration occur at the 3 -position.

A useful method for selective O-acetylation of 5,7-dihydroxyisoflavones has been described. Acetic anhydride and pyridine gives the 7-acetoxy-compound whereas acetic anhydride and perchloric acid yields the 5-acetoxy-isomer nuclear chlorination of the latter occurred at C-8 when it was treated with ethyl AW-dichlorocarbamate. Interaction of isoflavones (222) with Grignard reagents and copper(l) chloride gave the deoxybenzoin (223), which was used in the synthesis of stilbene-like compounds. ... 

Boersma BJ, Patel RP, Kirk M, Darley-Usmar VM, Barnes S. Chlorination and nitration of soy isoflavones. Arch Biochem Biophys 1999 368 265-275. 

Isoflavones have been shown to be beneficial in several chronic diseases in which oxidants are involved. Isoflavones are weak antioxidants when tested in vitro in die context of scavenging lipid peroxyl radicals. However, at sites of mflammation proinflammatory oxidants such as peroxynitrite (ONOO"), hypochlorous acid (HOCl), and hypobromous acid (HOBr) are formed that may also react widi isoflavones. We present evidence herein, using reverse-phase HPLC-mass spectrometry and proton NMR, that at concmitrations of diese oxidants formed at these local sites, nitration, chlorination, and bromination of isoflavones occurs. 

In die present study we have shown that the isoflavones can react with proinflammatory oxidants to form novel derivatives. By using LC-MS we have confirmed that isoflavones react widi HOBr to form mono- and dibrominated derivatives. These results correlate to the chlorination and nitration of die isoflavones our laboratory previously reported (20). Mono- and dichlorinated isoflavones were formed when reacted widi HOCl. Nitration of die isoflavcmes also occurs when reacted with ONOO. Nitration occurs at die C3 site of B-ring of the molecule. 

In our previous study (20), sites of chlorination were determined by proton NMR. It is likely diat the reaction between the isoflavones and HOBr results in die formation of multiple brominated isomers. Given die similar reaction, we propose the sites of bromination are similar to diat of chlmination, namely at the C6, C8, or C3 sites (Figure 1). 

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