BETULACEAE

The Betulaceae or birch family consists of 6 genera and over 100 species of deciduous, mostly monoecious trees and shrubs, mainly native to the Northern Hemisphere.

• Leaves alternate, simple
• Male flowers in long, drooping catkins; female flowers in short catkins or clusters; stamens 2–10 in the axils of the bracts
• Fruit a nut or nutlet

Betula alba & Betula pendula

Silver birch

Family Betulaceae

Description

Deciduous tree to 25 m tall. Bark black and fissured towards base of trunk, silver-white and peeling above. Branches slender and more or less pendulous. Leaf buds scaly but not sticky. Leaves alternate, simple; lamina 3–6 × 1.5–5.5 cm long, ovate to triangular, acuminate, glabrous; margins double toothed. Petiole about 2 cm long. Leaves turn yellow in autumn. Flowers monoecious with male and female flowers in different inflorescences—male flowers in drooping catkins 3–6 cm long with 2 stamens; female flowers in erect cylindrical/ovoid catkins up to 3.5 cm long. Wind pollinated. Fruit a flattened winged nutlet with persistent styles. Flowers in spring.

Odour—faintly aromatic; taste—somewhat bitter.

Habitat and cultivation

Native to Britain and Europe, Betula alba is cultivated elsewhere for its graceful beauty. It grows from seed and is available from garden centres. It can become naturalized. Drought tender, frost resistant.

Parts used

The young leaves and the bark but the sap and leaf buds may also be used. The parts are best harvested in spring.

Active constituents

1) Volatile oil (min. 0.5%) containing over 50 constituents including α-copaene, germacrene D, δ-cadinene and betulenols1

2) Flavonoids (approx. 3%) mainly hyperoside and avicularin, also luteolin, quercetrin and myricetin glycosides.^2,3 Flavonoid levels decrease with the age of the leaves²

3) Saponins—triterpene and steroidal including betulin (10%–30%),⁴ betulinic, papyriferic, pendulic and betuloleanolic acids⁵ and betufernanediols A and B.⁶ The presence of saponins in Betula leaves has been questioned and it has been proposed that dammarane esters, not their glycosides (saponins), are present.⁷ Betulin apparently gives the bark its white colour

4) Tannins of the hydrolysable type⁸

5) Resin

Also contains methyl salicylic acid (possibly present only after distillation and as a result of a chemical alteration), fatty acids, sterols,⁹ phenolics based on gallic, chlorogenic and coumarolyloquinic acids¹⁰ and lignan glycosides based on secoisolariciresinol¹¹ The inner bark also contains lignan glycosides, condensed tannins¹² and di- and trisaccharides.¹³

The chemistry of Betula can vary with geographic location, age, nutrients, part used and genetic make-up.^11,14 There is a degree of hybridization amongst the species.¹⁵

Nutritional constituents

Minerals: Potassium, calcium, zinc and phosphorus

Actions

1) Diuretic

2) Antilithic

3) Astringent

4) Cholagogue

5) Bitter

Scientific information

Although Betula species have been used for centuries there is little pharmacological information readily available for whole plant extracts. The oil of the related North American black birch, B. lenta, is often used to produce “wintergreen oil” because it is chemically very like that of Gaultheria procumbens.

Betula has been used in the food industry (it is used to flavour root beer for example) and in cosmetics as the essential oil has a good fragrance. Either the whole extract or the single constituent, betulin, is used.

In vitro:-

• the bark induces interferon production in cell culture in response to infection with the hepatitis C virus¹⁶
• betulin is anti-oxidant,¹⁷ cytoprotective against alcohol damage in liver cells,¹⁸ antiviral,¹⁹ anti-inflammatory²⁰ and cytoprotective against cadmium^21,22
• betulinic acid is anti-inflammatory,²⁰ antiviral¹⁹ (including derivatives that strongly inhibit HIV),²³ antimalarial²⁴ and anti-oxidant.¹⁷ It is also showing some promise as an antitumour agent.^25–28 Its concentration in Betula is however quiet low⁴

Both betulin and betulinic acid are strong inhibitors of phospholipase A2.²⁹

Medicinal uses

Cardiovascular system

• congestive heart failure
• fever

Urinary tract

• cystitis
• lithiasis
• oedema of renal origin

Musculoskeletal

• rheumatism
• arthritis
• gout

Skin

• inflammatory skin conditions

Externally

• arthritis
• neuralgia

Pharmacy

Three times daily

For leaves and bark

Infusion/Decoction of dried herb	–   1–4 g
Tincture 1:5	–   1–5 ml

Other applications

Birch Tar Oil alone, or formulated as a compound, is listed in the British Pharmaceutical Codex and has been used externally for the treatment of eczema and psoriasis.

The volatile oil and resin together are known as “empyreumatic oil of birch”.

Precautions and/or safety

There are a significant number of people who develop respiratory allergies to the pollen of Betula spp.30,31 There is no indication however that this sensitivity extends to use of the above medicinal preparations.

Historical uses

For sore mouths (as a wash); intermittent fevers (inner bark), analgesic; as a hair conditioner.