Horse chestnut: Background. Actions

Historical Note

The horse chestnut tree is commonly found in ornamental gardens throughout Europe, growing up to 35 metres in height. The seeds are not edible due to the presence of alkaloid saponins, but both the dried seeds and bark of the horse chestnut tree have been used medicinally since the 1 6th century. The seeds are also used for the children’s game ‘conkers’ and were used to produce acetone during World Wars I and II. In modern times, a dry extract referred to as horse chestnut seed extract (HCSE) is standardised to contain 1 6-21 % triterpene glycosides (anhydrous escin). HCSE has been extensively researched for its beneficial effects and is commonly used by general practitioners in Germany for the treatment of chronic venous insufficiency. Homoeopathic preparations of both the leaf and seed are also used for treating haemorrhoids, lower back pain, and varicose veins and the buds and flower are used to make the Bach flower remedies chestnut bud and white chestnut. The active component escin is also used intravenously and topically in cosmetics.

Other Names

Aescule, buckeye, chestnut, Castano de Indias, graine de marronier d’inde, escine, eschilo, hestekastanje, hippocastani semen, marron europeen, marronnier, ro╬▓kastaniensamen, Spanish chestnut

Botanical Name / Family

Aesculus hippocastanum (family [Sapindaceae] Hippocastanaceae).

It should be differentiated from Aesculus chinensis, Aesculus turbinate, Aesculus indica, Aesculus californica and Aesculus glabra.

Plant Parts Used

Seed. Less commonly bark, flower, and leaf.

Chemical Components

Horse chestnut seed contains 3-5% escin (aescin), a complex mixture of triterpene saponins (including the triterpene oligoglycosides escins Ia, Ib, IIa, IIb, and IIIa), the acylated polyhydroxyoleanene triterpene oligoglycosides escins IIIb, IV, V, and VI and isoescins Ia, Ib, and V, and the sapogenols hippocaesculin and barringtogenol-C, flavonoids (including flavonol oligosides of quercetin and kaempferol), condensed tannins, quinines, sterols (including stigmasterol, alpha-spinasterol, and beta-sitosterol), sugars (including glucose, xylose, and rhamnose), and fatty acids (including linolenic, palmitic, and stearic acids). It also contains the toxic glycoside esculin (aesculin), a hydroxycoumarin that may increase bleeding time due to antithrombin activity (NMCD2006).

Horse chestnut bark and flowers also contain the sterols stigmasterol, alpha-spinasterol and beta-sitosterol (NMCD 2006).

Although the majority of trials in the scientific literature have focused on the benefits of the HCSE extract, some authors suggest that the flavonoids contained in A. hippocastanum may provide additional benefits.

Main Actions

The major benefits of A. hippocastanum are related to its ability to prevent the degradation of vascular walls, maintaining vascular integrity and in turn preventing vascular hyperpermeability and the resulting oedema.

VASOPROTECTIVE/NORMAUSES VASCULAR PERMEABILITY

Horse chestnut appears to prevent the activation of leucocytes and therefore inhibit the activity of lysosomal enzymes (hyaluronidase and possibly elastase) involved in the degradation of proteoglycan (the main component of the extravascular matrix), thus reducing the breakdown of mucopolysaccharides in vascular walls. Escin is the major constituent thought to be responsible for the inhibitory effects on hyaluronidase. Interestingly, ruscogenins found in Ruscus aculeatusl. (butcher’s broom) while ineffective on hyaluronidase activity exhibits significant anti-elastase activity, which may explain the practice by many herbalists of combining the two herbs.

By reducing degradation, the synthesis of proteoglycans is able to occur, which reduces capillary hyperpermeability, preventing the leakage of fluid into intercellular spaces that results in oedema. The anti-exudative activity appears to be mediated by PGF2╬▒. In animal studies the escins la, lb, lla, and lib have been shown to reduce capillary hypermermeability induced by histamine, ascetic acid, carrageenan and serotonin.

Aesculus hippocastanum promotes the proliferation behaviour of human endo-thelial cells in vitro in a dose-dependent manner and may therefore also play a role in maintaining as well as protecting vascular walls.

By improving vascular tone, horse chestnut standardised extract (HCSE) may improve the flow of blood back to the heart, as demonstrated in animal studies in which it significantly increased, within normal arterial parameters, femoral venous pressure and flow, as well as thoracic lymphatic flow.

ANTI-OEDEMA

By inhibiting the degradation of vascular walls, horse chestnut prevents the excessive exudation of fluid through the walls of the capillaries that would result in oedema. In animal experiments HCSE (horse chestnut standardised extract) reduces oedema of both inflammatory and lymphatic origin. Escin also appears to possess a weak diuretic activity (NMCD 2006), which may support its anti-oedematous action.

ANTI-INFLAMMATORY

In animal studies the escins la, lb, lla, and lib have been shown to reduce capillary hyperpermeability induced by histamine, ascetic acid, carrageenan and serotonin. A sterol extract of horse chestnut bark was shown to have anti-inflammatory effects comparable to calcium phenylbutazone in a study of rats with carrageenan-induced paw oedema.

ANTIOXIDANT

HCSE (horse chestnut standardised extract) dose-dependently inhibits both enzymatic and non-enzymatic lipid peroxidation in vitro.

Other Actions

Animal studies have demonstrated that isolated escins la, lb, lla, and lib inhibit gastric emptying time and ethanol absorption, and exert a hypoglycaemic activity in the oral glucose tolerance test in rats.