Piptoporus betulinus: The Birch Bracket Mushroom Benefits & Identification

Synonyms

Agarico-pulpa pseudoagaricon Paulet
Boletus betulinus Bull.
Boletus suberosus Batsch
Boletus suberosus Wulfen
Fomes betulinus (Bull.) Fr.
Placodes betulinus (Bull.) Quél.
Polyporus betulinus (Bull.) Fr.
Ungularia betulina (Bull.) Lázaro Ibiza
Ungulina betulina (Bull.) Pat.

Common names

Birch bracket
Birch conk
Birch polypore
Razor strop

Description

Fruiting body: nearly round, becoming shelf-like or hooflike at maturity; tough or corky when fresh, rigid and hard when dry.
Cap: 5-25 cm wide, 2-6 cm thick, kidney-shaped to nearly round in outline, convex to nearly plane; surface covered by a thin, smooth, or suedelike, white to buff, tan, brown, or grayish-brown crust that often breaks up into scales or flat patches or wears away, revealing the whitish surface underneath; margin thick, blunt, involute, curblike (projecting below the pore surface), sometimes wavy.
Flesh: rubbery (becoming corky at maturity), thick, white.
Pores: appearing recessed due to curblike margin, 2-4 per mm; white when young, later becoming pale brown or grayish-brown and occasionally torn-up or toothlike; tubes 2-10 mm long, one layer only.
Stalk: sessile or present only as a thickened extension of the cap; lateral or attached to the top of the cap.
Sporeprint: white.
Spores: 3-6 x 1.5-2 µm, cylindrical to sausage-shaped, smooth.
Habit and habitat: solitary, scattered or in overlapping groups or columns on dead or sometimes living birch trees; common year-round in the Northern hemisphere where birch is found.

Piptoporus betulinus is one of the most common polyporus bracket fungi and grows almost exclusively on Birch trees. The brackets burst out from the bark of the tree, and these fruiting bodies can last for more than a year. Technically, it is an edible mushroom, with a strong, pleasant “mushroomy” odor but a bitter taste, with younger specimens being more palatable. Wood decayed by the fungus, and cultures of its mycelium, often smell distinctly of green apples.

The velvety cut surface of the fruiting body have been used as a strop for finishing fine edges on razors. Dried specimens have also been used as tinder, and this fungus (along with Fomes fomentarius) was carried by “Ötzi the Iceman” – the 5,000 year old mummy found in the Tyrol (Peintner et al., 1998).

It is a necrotrophic parasite on weakened Birches, and will cause brown rot and eventually death, being one of the most common fungi visible on dead Birches. It is likely that the birch bracket fungus becomes established in small wounds and broken branches and may lie dormant for years, compartmentalised into a small area by the tree’s own defence mechanisms, until something occurs to weaken the tree. Fire, drought and suppression by other trees are common causes of such stress.

Bioactive compounds

A detailed phytochemical analysis of distillation products has been performed on the birch bracket, leading to the identification of various chemicals, including aliphatic alcohols, ketones, aldehydes, terpenes, and aromatic compounds (Rösecke et al., 2000).

Six lanostane-type triterpene acids have been isolated from the fruiting bodies of P. betulinus. These compounds have been identified as polyporenic acids A and C, three derivatives of polyporenic acid A (3-5), and a novel compound, (+)-12α,28-dihydroxy- 3α- (3′-hydroxy-3′-methylglutaryloxy)- 24-methyllanosta-8,24(31)- dien-26-oic acid. All these compounds had antiinflammatory properties, as demonstrated by the ‘mouse ear inflammation assay’. This assay tests antiinflammatory potential by determining how much a compound suppresses the edema normally caused by the chemical 12-O-tetradecanoylphorbol-13-acetate (TPA) on mouse ears. In these experiments, the birch bracket-derived compounds inhibited edema by 49-86% with a 400 nmol/ear application (Kamo et al., 2003).

It was shown several decades ago that polyporenic acid A occurs in Piptoporus betulinus mainly in the form of conjugates in which the 3-α-hydroxyl group is esterified to acetic, caproic, malonic and β-hydroxy-β-methylglutaric acids. The dibasic acid conjugates occur not only as the free acids but also partly as monomethyl esters (Bryce et al., 1967).

The hydroquinone (E)-2-(4-hydroxy-3-methyl-2-butenyl)-hydroquinone, and known compound, polyporenic acid C, were isolated as matrix metallo-proteinase (MMP) inhibitors from P. betulinus (Kawagishi et al., 2002). MMPs are proteins that break down other structural proteins in the cell, and are though to be involved in a number of important biological processes, including cell proliferation, migration, differentiation, angiogenesis, apoptosis and host defense.

Medicinal properties

Antimicrobial/antiviral activity

Piptamine (molecular formula C₂₀H₃₅N₃) is an antibiotic produced by this mushroom (Schlegel et al., 2000). Both methanol and dichloromethane extracts proved to be antibacterial towards Bacillus subtilis and Escherichia coli, while the dichloromethane extract had a further molluscicidal activity to Biomphalaria glabrata (Keller et al., 2002).

Nucleic acids isolated from P. betulinus have antiviral activity. Specifically, they reduced the number of vaccinia virus plaques in chick embryo fibroblast (CEF) tissue culture. Furthermore, when administered intravenously to white mice, birch bracket nucleic acids protected them against lethal infection with a tick borne encephalitis virus (Kandefer-Szerszen et al., 1979). Crude RNA from P. betulinus can induce human fibroblasts to produce interferon with a specific activity of 400 units per mg of protein (Kandefer-Szersen and Kawecki, 1974; Kawecki et al., 1978).

Antitumor activity

Polysaccharides extracted from the mycelial culture of P. betulinus and administered intraperitoneally into white mice at a dosage of 300 mg/kg inhibited the growth of Sarcoma 180 and Ehrlich solid cancers by 90% (Ohtsuka et al., 1973).

Bryce TA, Campbell IM, McCorkin NJ.
Metabolites of polyporaceae .I. Novel conjugates of polyporenic acid A from Piptoporus betulinus.
Tetrahedron. 1967 23(8):3427-&.

James PG, Cherniak R.
4-Methylmorpholine N-oxide-methyl sulfoxide soluble glucan of Piptoporus betulinus.
Carbohydr Res. 1990 206(1):167-72. No abstract available.

Kamo T, Asanoma M, Shibata H, Hirota M.
Anti-inflammatory lanostane-type triterpene acids from Piptoporus betulinus.
J Nat Prod. 2003 66(8):1104-6.

Kandefer-Szerszen M, Karpinska T, Kawecki Z.
The influence of inhibitors of cellular synthesis and UV irradiation on interferon induction by RNA from Piptoporus betulinus.
Arch Immunol Ther Exp (Warsz). 1982 30(1-2):25-31.

Kawagishi H, Hamajima K, Inoue Y.
Novel hydroquinone as a matrix metallo-proteinase inhibitor from the mushroom, Piptoporus betulinus.
Biosci Biotechnol Biochem. 2002 66(12):2748-50.

Keller C, Maillard M, Keller J, Hostettmann K.
Screening of European fungi for antibacterial, antifungal, larvicidal, molluscicidal, antioxidant and free-radical scavenging activities and subsequent isolation of bioactive compounds.
Pharm Biol. 2002 40(7):518-25.

Peintner U, Poder R, Pumpel T.
The iceman’s fungi.
Mycol Res. 1998 102:1153-62.

Rösecke J, Pietsch M, Konig WA.
Volatile constituents of wood-rotting basidiomycetes.
Phytochem. 2000 54(8):747-50.

Schlegel B, Luhmann U, Hartl A, Grafe U.
Piptamine, a new antibiotic produced by Piptoporus betulinus Lu 9-1.
J Antibiot (Tokyo). 2000 53(9):973-4. No abstract available.

Jelsma J, Kreger DR.
Observations on the cell-wall compositions of the bracket fungi Laetiporus sulphureus and Piptoporus betulinus.
Arch Microbiol. 1978 119(3):249-55.

Kandefer-Szerszen M, Kawecki Z.
Ether extracts from the fruiting body of Piptoporus betulinus as interference inducers.
Acta Microbiol Pol A. 1974 6(2):197-200. No abstract available.

Kandefer-Szerszen M, Kawecki Z, Guz M.
Fungal nucleic acids as interferon inducers.
Acta Microbiol Pol. 1979 28(4):277-91.

Kawecki Z, Kaczor J, Karpinska T, Sujak I, Kandefer-Szerszen M.
Studies of RNA isolated from Piptoporus betulinus as interferon inducer.
Arch Immunol Ther Exp (Warsz). 1978 26(1-6):517-22.

Ohtsuka S, Ueno S, Yoshikumi C, Hirose F, Ohmura Y, Wada T, Fujii T, Takahashi E.
Polysaccharides having an anticarcinogenic effect and a method of producing them from species of Basidiomycetes.
UK Patent 1331513, 26 September 1973.

Wangun HV, Berg A, Hertel W, Nkengfack AE, Hertweck C.
Anti-inflammatory and anti-hyaluronate lyase activities of lanostanoids from Piptoporus betulinus.
J Antibiot (Tokyo). 2004 57(11):755-8. No abstract available.