Rutin

Rutin is the glycoside combining the flavonol quercetin and the disaccharide rutinose. It is a flavonoid glycoside found in a wide variety of plants, including citrus.

Occurrences

Rutin is one of the phenolic compounds found in the plant species Carpobrotus edulis. Its name comes from the name of Ruta graveolens, a plant that also contains rutin. Various citrus fruit peels contain 32 to 49 mg per g of flavonoids expressed as rutin equivalents. Citrus leaves contain rutin at concentrations of 11 g per kg in orange trees and 7 g per kg in lime trees.
In 2021, Samoan researchers identified rutin in the native plant matalafi.

Metabolism

The enzyme quercitrinase found in Aspergillus flavus is in the rutin catabolic pathway.

In food

Rutin is a citrus flavonoid glycoside found in many plants, including buckwheat, the leaves and petioles of Rheum species, and asparagus. Tartary buckwheat seeds have been found to contain more rutin than common buckwheat seeds. Rutin is one of the primary flavonols found in 'clingstone' peaches. It is also found in green tea infusions.
Approximate rutin content of selected foods, in milligrams per 100 grams or milliliters:

Numeric	Alphabetic
389	Tartary buckwheat, roasted bran
332	Capers, spice
68	Tartary buckwheat, roasted grain
45	Olive, raw
36	Buckwheat, whole grain flour
32	Green tea, infusion
23	Asparagus, raw
19	Black raspberry, raw
17	Black tea, infusion
11	Red raspberry, raw
9	Buckwheat, groats, thermally treated
6	Buckwheat, refined flour
6	Greencurrant
6	Plum, fresh
5	Blackcurrant, raw
4	Blackberry, raw
3	Tomato, whole, raw
2	Prune
2	Fenugreek
2	Marjoram, dried
1	Grape, raisin
1	Zucchini, raw
1	Apricot, raw
0	Apple
0	Redcurrant
0	Grape
0	Tomato, whole, raw

Research

Rutin and other dietary flavonols are under preliminary clinical research for their potential biological effects, such as in reducing post-thrombotic syndrome, venous insufficiency, or endothelial dysfunction, but there remains no high-quality evidence for their safe and effective uses, as of 2018. A 2020 review indicated that oral rutosides may reduce leg edema by a small amount in people with post-thrombotic syndrome, but the risk of adverse effects was higher.
As a flavonol among similar flavonoids, rutin has low bioavailability due to poor absorption, high metabolism, and rapid excretion that collectively make its biological properties in vivo difficult to study, and its potential for use as a therapeutic agent limited.

Biosynthesis

The biosynthesis pathway of rutin in mulberry leaves begins with phenylalanine, which produces cinnamic acid under the action of phenylalanine ammonia lyase. Cinnamic acid is catalyzed by cinnamic acid-4-hydroxylase and 4-coumarate-CoA ligase to form p-coumaroyl-CoA. Subsequently, chalcone synthase catalyzes the condensation of p-coumaroyl-CoA and three molecules of malonyl-CoA to produce naringenin chalcone, which is eventually converted into naringenin flavanone with the participation of chalcone isomerase. With the action of flavanone 3-hydroxylas, dihydrokaempferol is generated. DHK can be further hydroxylated by flavonoid 3´-hydroxylase to produce dihydroquercetin, which is then catalyzed by flavonol synthase to form quercetin. After quercetin is catalyzed by UDP-glucose flavonoid 3-O-glucosyltransferase to form isoquercitrin, finally, the formation of rutin from isoquercitrin is catalyzed by flavonoid 3-O-glucoside L-rhamnosyltransferase.