Rutin is a type of polyphenol called a flavonoid glycoside. It’s composed of quercetin and the disaccharide rutinose. It’s also called rutoside, quercetin-3-O-rutinoside and sophorin. While it’s found in a wide variety of plants, including citrus, foods with the highest concentrations of rutin include capers, black olives, buckwheat, and asparagus. The most common use of rutin has been for supporting healthy veins. But it does much more.