Horse chestnut powder is made from the fruits of Aesculus hippocastanum, a deciduous tree in the soapberry family that is native to the Balkan forests of southeastern Europe. Also known as conker tree and buckeye, horse chestnut is known to be a source of aescin (or escin). It is also a naturally occurring source of antioxidant flavonoids, such as quercetin and kaempferol. Horse chestnut powder may be taken in capsule form or applied topically.