FAMILY FAGACEAE — FAGACEAE
Monoecious trees with simple, alternate leaves; flowers are unisexual with an inconspicuous, simple perianth. Male flowers are grouped in catkins, while female flowers are clustered in groups, with an inferior ovary. The fruit is a nut (acorn) sitting in a hard cupule formed from fused bracts.
The family includes three genera: oak (Quercus), whose bark is used in scientific medicine; chestnut (Castanea), whose nuts are used as food; and beech (Fagus), from which beech tar and creosote (5%) were historically derived. Creosote is a mixture of polyphenols, the most important being guaiacol, which has bactericidal properties (formerly used in tuberculosis treatment); tar and creosote were also applied in skin disease treatments.
Tannins of the pyrogallol group are common, especially in the bark of trees. The highest concentration is found in pathological growths (galls) that frequently develop on the leaves and shoots of Quercus. Wood, leaves, and fruits contain smaller amounts of tannins. Among flavonoids, the glycoside quercitrin and its aglycone quercetin are the most frequently found. Seeds are rich in starch (Quercus, Castanea), while beech nuts contain about 40% fatty oil and a small amount of starch.
The tree grows to large sizes. The trunk is covered with dark gray bark marked by numerous longitudinal cracks; the trunks of young trees (up to 20 years) and thin branches of older ones are covered with smooth, shiny bark known as «mirror bark.» Leaves are dark green, leathery, oblong-obovate, with deeply lobed edges, and they fall in winter. The fruit is an acorn surrounded by a cupule; acorns sit on long peduncles.
Widely distributed in the middle zone of the European part of Russia in the forested area; it reaches as far north as Leningrad. It is one of the main tree species in the deciduous forest zone and the forest-steppe region, extending further south into the steppe, where it grows along rivers, ravines, and gullies. Its easternmost range reaches the Ural Mountains. It does not grow in Siberia. Oaks are significant for creating shelterbelts in the steppe zone.
In medicine, oak bark (Cortex Quercus) is used. Collection is allowed only in areas designated for logging by forestry authorities. In early spring, before the leaves appear, mirror bark is collected from young trees with trunk diameters of 10–20 cm (saplings). When mature trees are felled, bark is removed from young branches. The bark is collected in tubular or trough-shaped pieces up to 30 cm long and 2–3 mm thick. The outer surface is smooth, with transversely elongated lenticels, light brown, matte, or silvery shiny (mirror-like); the inner surface is yellowish-brown, with numerous longitudinal protruding ridges.
The bark contains 10–20% tannins of the pyrogallol group (only 2–4% in old bark), free ellagic and gallic acids, the flavonoid quercetin, and its glycoside quercitrin.
The Pharmacopoeia of the 10th edition requires that the bark contain at least 8% tannins.
It is used as a decoction in an astringent and anti-inflammatory capacity for rinsing the mouth and throat (10–20 g per 200 ml). Boil for 15–20 minutes. It is included in mouthwash collections in combination with linden flowers.
Winter oak (Quercus petraea Liebl., Q. sessiliflora Salisb.) is listed in the 10th edition of the Pharmacopoeia. It grows in the Black Sea region, the western Caucasus, and is cultivated in the European part of Russia.
In the wild, there are 19 species, with two species found in the Far East and several species occurring in Crimea. The Caucasus has a great diversity of oak species, some forming extensive forests in the North Caucasus and especially in Transcaucasia, though few have been studied.