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Old 06-02-08, 03:29 PM
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Re: Problems with onions???

I forgot the cooked part. Onions get sweeter when cooked that could be the fructose polymer fructan breaking down. Suggesting fructan again.

Quercetin has a high melting point so I'm assuming its not destroyed in the cooking process. Different strains of onions may have different levels. And the ones being cooked maybe low in quercetin.


Various saponins in onions, "Among the tested compounds, elburzensosides C1/C2 and agapanthagenin showed the highest activity in reducing induced contractions as measured by the reduction of histamine release by about 50 %".


http://en.wikipedia.org/wiki/Saponin

Quote:
Onion (red variety)
"As active compounds in onion extracts, thiosulfinates and cepaenes could be identified. They exert a wide spectrum of pharmacologic activities".


Five alk(en)ylsulfinothioic acid alk(en)yl-esters isolated from onions and four synthetic thiosulfinates inhibited 5-lipoxygenase of porcine leucocytes, histamine release and leukotriene B4 and C4 biosynthesis of human polymorphonuclear leucocytes, thromboxane B2 biosynthesis by human platelets and allergen- and PAF-induced bronchial obstruction of guinea-pigs. The anti-asthmatic and anti-inflammatory effects of onions depend in part on the thiosulfinate moiety.


Cooking onion certainly alters the concetration of some of its sulfur compounds. Based on the simple fact they get milder.

If we had a $50,000 HPLC machine we could fractionate raw onion and cooked onion extract and find what fraction caused the problem. Determine that it has been reduce in cooking. Then make a 50 mg sample or so and send it off for NMR analysis to figure out what compound it is.
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