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- Birch (Betula spp., Betulaceae)
- Traditional Uses
- Phytochemistry
- Pharmacology
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Date:
09-15-2015 | HC# 031542-528
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Re: Traditional Uses and Pharmacological Properties of the Genus Betula
Rastogi S, Pandey MM, Rawat AKS. Medicinal
plants of the genus Betula –
traditional uses and a phytochemical-pharmacological review. J Ethnopharmacol. January 15,
2015;159:62-83.
Birch (Betula
spp., Betulaceae) bark and bark extracts from this genus of trees and shrubs
found in temperate and boreal zones of the Northern Hemisphere are used in the
medical traditions of many regions, often for inflammatory conditions such as
arthritis. These authors conducted a comprehensive electronic literature search,
and review the botany, traditional uses, phytochemistry, pharmacology, and
toxicology of birches, discussing therapeutic potential and research needs.
Listed ethnomedicines from every area of
birches' distribution include decoctions, teas, baths, pastes, poultices, and
powders made from bark, leaves, resin, buds, sap, stems, aerial parts, flowers,
roots, cork, and whole plants. Bone-related uses are most common, including
microfractures, dislocations, rheumatism, arthritis, and gout. Other reported
uses are for urinary and renal ailments, edema, lithiasis, heart problems, skin
conditions, hypercholesterolemia, wounds, and burns, among many others. Birch
is also used for hair loss. In anthroposophic medicine, its extracts were used
in rheumatic diseases. Birches yield sugar, vinegar, and beer. Sweet birch (B. lenta) is the main source of oil of
wintergreen. Leaf extracts, used as whitening agents in cosmetics, are
traditionally used against freckles. Birch bark is a traditional food
preservative; in Northern Pakistan it is used to enhance the flavor of ghee
during aging. Waterproof, it is also utilized to temporarily cover buildings
under construction and to protect harvested crops. In the Himalayan region of
India, Himalayan birch (B. utilis) is
used in religious ceremonies.
While naming many species and their habitats,
distribution, and uses, the authors note that the taxonomy of European birches
is disputed due to morphological variability and hybridization. Inability to
distinguish among closely related species has prompted biometric and
chemotaxonomic studies, as well as studies of phylogenetic relationships. Chemotaxonomic
studies have focused mainly on phenolics (flavonoids and terpenoids) in birch
bark, leaves, buds, and stems. This review lists 137 triterpenoids (from the
ocotillol; dammarane type I, II, III, and IV; oleanane; and lupane groups);
diarylheptanoids (cyclic and acyclic); phenylbutanoids; phenolics; flavonoids,
flavones, and flavanones; catechins and lignans; steroids; and miscellaneous
compounds from birches, with the
species from which they were isolated. More importantly, the chemical
composition of extracts can vary significantly between plant parts and
processing methods. Three triterpenoids – betulin, betulinic acid, and lupeol,
belonging to the lupane group and found in all birches – are especially
noteworthy, as is papyriferic acid, secreted by glands on twigs during only the
juvenile ontogenetic phase of resin-producing tree birches. Several reviews of
betulin, lupeol, and betulinic acid have been published. Accompanying figures
illustrate the chemical composition and basic structure of these compounds.
Pharmacological studies report anticancer,
anti-inflammatory, antiarthritic, antioxidant, antimicrobial, antiviral,
dermatological, immunomodulatory, hepatoprotective, antidiabetic, gastroprotective,
and other effects for birch species, parts, extracts, and compounds. For
example, anticancer effects from several birch species and/or extracts have
been reported against 12 different human and murine cancer cell lines. Against
A431 skin epidermoid carcinoma, the 70-80% inhibition of proliferation seen in
vitro for a silver birch (B. pendula)
bark extract and its two main constituents, betulin and betulinic acid, may be
of practical significance; a pilot study of a birch bark ointment in actinic
keratosis also reported efficacy with no adverse effects after two months of use.
In an MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide] assay
using four cancer cell lines comparing several betulin-enriched extracts, all
of the prepared bark extracts exerted a pronounced antiproliferative effect
against human cancer cell lines. The substantial differences in betulin and
betulinic acid content were not reflected in antiproliferative activity. While
this may be attributed to other active natural birch compounds, including
flavonoids, the authors comment on the micromolar and even nanomolar quantities
needed for birch's effects to occur, comparable to some synthetic drugs. An
evaluation of birch triterpenes against human cancer and multidrug-resistant
(MDR) cell lines, while reporting no significant differences in cytotoxicities
of the tested compounds against sensitive and resistant cell lines, found that cytotoxicity
for several compounds in resistant lines was enhanced in the presence of
non-toxic amounts of colchicine or doxorubicin, raising the possibility of MDR
reversal. Papyriferic acid, which in nature protects immature birches from
browsing by mammals, has also been studied in MDR cancer cells; several of its
derivatives exhibit potent MDR-reversing ability.
While most studies of birch and birch extracts
have been in vitro or in vivo, a few human trials besides the skin cancer pilot
study mentioned are referenced. It was reported that white birch (B. pubescens syn. B. alba) leaves and buds have been used to treat uterine cancer; no
details are provided. Also, a study of a white birch extract in chronic
hepatitis reported subjective symptom reductions as well as objective outcomes,
and monitored safety and compliance.
Pharmacological studies support traditional
uses of birch bark and birch extracts in bone-related problems such as
degenerative joint disease and demonstrate a variety of effects that contribute
to bone and joint health. Traditional use in wound healing, hypercholesterolemia,
and bile disorders is also supported. While no ethnopharmacological link seems
to exist between traditional uses and the current interest in birch extracts as
novel anticancer compounds, many traditional uses imply modification of the
cell cycle, and the pharmacological evidence for these compounds is strong.
Controlled, clinical trials are needed to determine if there is a basis for
other traditional uses and claims.
—Mariann
Garner-Wizard
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