Isorhamnetin
Introduction '''Isorhamnetin''' is an O-methylated flavon-ol from the class of flavonoids. A common food source of this 3'-methoxylated derivative of quercetin and its glucoside conjugates are pungent yellow or red onions, in which it is a minor pigment, quercetin-3,4'-diglucoside and quercetin-4'-glucoside and the aglycone quercetin being the major pigments. Pears, olive oil, wine and tomato sauce are rich in isorhamnetin. Almond skin is a rich source of isorhamnetin-3-O-rutinoside andisorhamnetin-3-O-glucoside, in some cultivars they comprise 75% of the polyphenol content, the total of which can exceed 10 mg/100 gram almond. Others sources include the spice, herbal medicinal and psychoactive Mexican tarragon ''(Tagetes lucida)'', which is described as accumulating isorhamnetin and its 7-O-glucoside derivate. Nopal (Opuntia ficus-indica (L.)) is also a good source of isorhamnetin, which can be extracted by supercritical fluid extraction assisted by enzymes.
Metabolism The enzyme quercetin 3-O-methyltransferase uses S-adenosyl methionine and quercetin to produce S-adenosylhomocysteine and isorhamnetin.The enzyme 3-methylquercetin 7-O-methyltransferase uses S-adenosyl methionine and 5,7,3',4'-tetrahydroxy-3-methoxyflavone (isorhamnetin) to produce S-adenosylhomocysteine and 5,3',4'-trihydroxy-3,7-dimethoxyflavone (rhamnazin).
Glycosides * Isorhamnetin-3-O-rutinoside-7-O-glucoside* Isorhamnetin-3-O-rutinoside-4'-O-glucoside* Narcissin (Isorhamnetin-3-O-rutinoside)
See also * List of antioxidants in food* List of phytochemicals in food* Tamarixetin, the 4'-methyl analog
References
External links *  Isorhamnetin on chemblink.com