Traditionally used to improve blood circulation
The horse chestnut tree (Aesculus hippocastanum) produces a seed that is used as a dietary supplement extract. Horse chestnut seed extract (HCSE) is a rich source of a nutrient called aescin (also escin), which is believed to be its biologically active compound.
Horse chestnut extract works in multiple ways to support the health of your capillaries and veins in your legs. It is a direct tonic substance for veins and valves, a source of nourishment that enhances their structure. It has been shown to close small gaps in veins that allow fluid leakage that contributes to edema. In addition to its structural support for veins and valves it has a regulating function relating to both capillaries and veins that involves ion channels and the flow of calcium in particular.
On the one hand, horse chestnut seed extract relaxes the endothelial lining of capillaries enhancing friendly nitric oxide production, and reducing minor swelling. This generally supports lower pressure or push coming from the arteries. It also helps seal up capillaries that leak too much water into the tissues, which helps reduce edema.
On the other hand, while assisting the structural integrity of veins and valves, horse chestnut seed extract increases the pressure in veins so they can pump blood more efficiently against gravity (as opposed to the relaxing effect it has on capillaries). It also helps improve flow through the closely related lymphatic system—another pressure system that can get backed up and cause circulation problems. This is a combination of beneficial actions that are helpful to lower leg circulation.