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 and isorhamnetin-3-O-glucoside, in some cultivars they comprise 75% of the polyphenol content, the total of which can exceed 10 mg/100 gram almond.PMID 25544797 PMC4276397 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.Abdala, 1999 Nopal (Opuntia ficus-indica (L.)) is also a good source of isorhamnetin, which can be extracted by supercritical fluid extraction assisted by enzymes.
Biosynthesis and metabolism The enzyme luteolin O-methyltransferase uses S-adenosyl methionine to methylate the flavanol, quercetin, giving isorhamnetin.
The enzyme 3-methylquercetin 7-O-methyltransferase further methylates isorhamnetin to produce rhamnazin.
Isorhamnetin is an inhibitor of CYP1B1.
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