HIPPOCASTANACEAE

The Hippocastanaceae family consists of 2 genera and about 15 species of mostly trees or large shrubs with opposite, compound leaves and large, terminal racemes or panicles of flowers. The fruit is a large capsule, either smooth or spiny, opening by 3 valves and usually containing one seed.

Aesculus hippocastanum

Horse chestnut

Family Hippocastanaceae

Description

A large deciduous tree 30 × 5 m, with a rounded crown and spreading branches. Trunk erect, stout and columnar; bark smooth, grey-green. Twigs stout, with very large reddish brown sticky buds. Leaves opposite, with 5–7 sessile leaflets. Central leaflets about 15–35 × 6–14 cm, obovate, irregularly crenate-serrate. Basal leaflets smaller. Flowers in broad-cylindric panicles to 30 cm high. Peduncles and pedicels glabrous or hairy. Calyx 4–6 mm long with fine short dense hairs inside. Petals 1–1.7 cm long with a narrow basal claw and the rest of the petal broad-oblong, very undulate and recurved, white with a yellow to red spot near the base. Filaments slender, hairy and curving downwards. Capsule to 6 cm wide, sub-globose, echinate. Seeds (conkers) 1–2, 3–5 cm wide, usually asymmetric, dark, shining brown with a prominent, white hilum. Flowers in spring, fruits in autumn.

Odour—slight; taste—bitter, acrid.

Habitat and cultivation

Native to Eastern Europe. Prefers to grow in rich, well-drained sandy loam in sunny, sheltered situations. Grown from seed sown in autumn or stratified, and will self-sow. Widely cultivated in cool climates. Drought and frost resistant.

Parts used

The fresh seed, harvested in autumn, when ripe. The bark and even the leaves have been used.

Active constituents1,2

1) Saponins—triterpenoid (up to 13%) containing “aescin” and “protosapogenin” or “prosapogenin”. Aescin itself exists in three forms—α-aescin, β-aescin and cryptoaescin. These are complex mixtures in themselves and β-aescin consists of more than 30 derivatives^3,4 of protoaescigenin and barringtogenol-C. Also contains hippocaesculin⁵

2) Flavonoids including quercetin, kaempferol and their derivatives

3) Tannins including proanthocyanidin A₂

The seeds also contain up to 7% fatty oil, triterpenes (including taraxerol, α- and β-amyrin),⁶ sterols,⁷ coumarins (esculin and fraxin)² and a lectin.⁸

Actions

1) Venous tonic

2) Astringent

3) Anti-inflammatory

Scientific information

Aesculus was introduced into Europe in the 16th century from Asia. Its constituent coumarin esculin was officially used in its glycoside form in external preparations for sunscreens and to treat haemorrhoids and internally for the treatment of capillary fragility.⁹ German Commission E has approved the herb's use for chronic venous insufficiency including varicose veins and oedema.

Most of the research on horse chestnut has concentrated on its effect on veins and the microcirculation. Extracts of Aesculus that have been used clinically have been standardised to around 70% β-aescin (referred to as aescin or escin) content, as this complex is considered to be the most significant contributor to the herb's activity.²

Circulatory system

In vitro—A number of pharmacological activities have been established for aescin which may provide an explanation for the actions of Aesculus on vein function in vivo.² It is:-

• anti-oedematous—through inhibition of hyaluronidase activity (may prevent breakdown of, and at the same time strengthen, capillary wall stopping oedematous leakage¹⁰), altered membrane permeability, reduced intercellular gaps in veins and reduced hypoxia of endothelial cells which via phopholipase-A2 can lead to inflammation that precedes oedema
• anti-inflammatory—as above and also through inhibition of leukocyte activation, reduced neutrophil adhesiveness and reduced release of inflammatory mediators
• venotonic—through blood vessel contraction, mediated through prostaglandin F₂α.² This occurs in normal and slightly dilated saphenous veins although not in more severely dilated or overtly varicosed ones, these being unresponsive to vasoactive drugs generally¹¹

The above pathogenic processes are closely interlinked and can exacerbate each other therefore aescin could intervene at various levels to ameliorate the development of venous insufficiency.²

In vivo—A topical preparation consisting of 1% aescin plus essential phospholipids was beneficial for:-

• acute inflammation due to histamine¹² or disturbed venous flow¹³
• severe venous incompetence, reducing capillary fragility and fluid leakage¹⁴
• venous microangiopathy reducing plasma free radical levels¹⁵
• superficial venous thrombosis¹⁶
• microcirculation in the skin of people with diabetes¹⁷ including those with neuropathy and small ulcerated lesions^18–21

This same combination used internally was diuretic.²² Aescin alone improved signs and symptoms of haemorrhoids and varicose veins and helped resolve post-operative oedema.²

Aesculus has been tested in the treatment of chronic venous insufficiency (CVI) and varicose veins. Some of its action is achieved by reducing the accumulation of oedematous fluid through decreased trans-capillary filtration.23 Internal use of the herb decreased the signs (oedema, erythema) and symptoms (pain, fatigue, heaviness of limb, itching) of CVI and improved general quality of life for people with the condition^24–28 (not corroborated²⁹). Aesculus improved venous insufficiency due to pregnancy too.¹ In early stage CVI it was as effective as compression stockings in reducing oedema, with better patient tolerance.³⁰ In advanced stages of the condition the stockings were more effective.³¹ Aesculus gave better improvement in the treatment of varicose ulcers, a consequence of CVI, when used with conventional strategies (compression stockings and dressings) than when conventional therapy was used alone.³²

Only one study to-date failed to find Aesculus of benefit in the treatment of CVI²⁹ and a number of reviews have concluded in favour of its efficacy for CVI and varicose veins.^33–37

The herb has also been successfully used:-

• as a prophylactic prior to surgical treatment in those with evidence of deep vein thrombosis³⁸
• to reduce oedema induced by flying¹
• in the treatment and prophylaxis of venous problems caused by the contraceptive pill³⁹
• in topical treatment of sprains and bruises.¹

Other

In vitro—Some of the saponins are cytotoxic⁵ and an unidentified glycoside inhibits sweet taste receptors.⁴⁰ The whole extract is a very good antioxidant.² Aescin is active against the virus responsible for SARS.⁴¹

In vivo—A gel containing 3% horse chestnut extract, through fibroblast contraction, reduced wrinkles.⁴²

Medicinal uses

Cardiovascular system

• varicose veins
• varicose ulcers
• haemorrhoids
• oedema
• arteriosclerosis
• thrombosis
• thrombophlebitis
• prophylactic against thrombosis

Gastro-intestinal tract

• gastritis
• enteritis

Externally

As an ointment it has been used to treat:

• varicose veins
• bruises
• sprains

Pharmacy

Three times daily
Fluid Extract	–   0.5–1.2 ml

Standardised extracts used have been based on 50–150 mg of aescin per day and topical preparations contained 1–2% aescin.¹

Pharmacokinetics

β-aescin is bioavailable to a variable extent depending on the particular formulation used.⁴³ It reaches maximum blood levels after 2 hours with a half life of between 6–8 hours,² although there appears to be considerable variation even for the same extract⁴⁴ and some diurnal variation too.⁴⁵

Precautions and/or safety

The extracts used in clinical trials were found to be safe and well tolerated.^25,28,33,36 Adverse reactions that have been reported for Aesculus/aescin preparations include gastro-intestinal disturbances, headaches, itching and dizziness.²

The unripe seed has caused poisoning in children. There are anecdotal reports of hepatic injury after intravenous use of an Aesculus extract⁴⁶ and contact dermatitis from a topical preparation.⁴⁷

A botanical preparation of which horse chestnut was a part was withdrawn from the market after cases of pseudo-lupus were connected to its use, however Aesculus was not considered the causative factor.^48,49

Renal failure has been observed in patients given intravenous50 or high oral doses of aescin.¹ No cases of renal problems have been attributed to Aesculus used at recommended doses.

Interactions

Aescin has been added, with benefit, to the treatment regime of AIDS patients to help prevent the crystallisation of indinavir that can occur in renal tubules.⁵¹

Historical uses

The bark was used as a febrifuge, tonic and narcotic—used in fevers and externally for ulcers. The seeds for coronary heart disease; dysentery; fevers rheumatism, neuralgia, menorrhagia, bronchitis, wounds, chilblains, prostatitis, constipation. Leaves used for whooping cough.