Picture source: Wikipedia
Agaricus auratus Paulet
Agaricus equestre L.
Agaricus flavovirens Pers.
Tricholoma auratum (Paulet) Gillet
Tricholoma flavovirens (Pers.) S. Lundell (see Deng and Yao, 2005)
Man on Horseback
Grünling Pilz (German)
Cap: 6-12 cm diameter, convex to plane or with margin elevated, surface viscid when moist, smooth, yellow to greenish-yellow or brownish-yellow, sometimes reddish-brown at the center and yellow towards the margin; may be faintly scaly.
Flesh: thick, firm, white, yellowish before the cap cuticle.
Gills: free, rounded at the stem, sulphur-yellow, close.
Stem: up to 8 cm tall and 2.0 cm thick, equal or slightly thicker at base, white, buff to tinged yellow, dry, smooth.
Spore print: white.
Spores: 6-8 x 4-5 µm, hyaline, ellipsoid, smooth.
Habitat: Scattered to densely gregarious in grassy or shrubby areas in soil, in coniferous woods, Aug-Oct.
Edibility: See toxicity section.
The methanol extract of Tricholoma equestre (referred to as T. aurantum in this paper) contains (22E,24R)-ergosta-7,22- diene-3β,5α,6β-triol (see below), a sterol that stimulates the enzyme alkaline phosphatase (ALP) in mouse bone cells (osteoblasts).
Higher levels of ALP enzyme activity are associated with increased proliferation and differentiation of osteoblasts, and the prevention of osteoporosis (for an example, see Choia et al., 2001). By performing assays with structurally related sterols, the researchers determined that the presence of hydroxyl moieties at carbons 5 and 6 has an important effect on the molecule's differentiation-inducing activity. Additionally, this compound protected these cells from apoptosis (cell-death) that normally results with serum starvation (Hata et al., 2002).
Using the disk diffusion and microdilution methods of antimicrobial determination, the chloroform extract of T. equestre was shown to have weak antibiotic activity against Escherichia coli, Staphylococcus aureus and S. epidermidis, and strong activity against Bacillus subtilis. The dichloromethane, acetone and ethanol extracts all showed similar weak activity against S. aureus, S. epidermidis and B. subtilis, while the ethyl acetate extract showed an additional weak activity against Pseudomonas aeruginosa (Yamac and Bilgili, 2006).
Although several guide books claim this species to be choice and edible (for example, see here), reports from France (Anonymous, 2001; Deffieux and Bendry, 2003; Massart, 2003) and Poland (Chodorowski et al., 2002) show evidence of the 'Man on Horseback' causing acute rhabdomyolosis (Deffieux and Bedry, 2003), an effect that was later replicated in rats. However, the reported poisoning happened with the consumption of a rather large quantity of mushrooms, and a later study (Nieminen et al., 2005) showed that the same effect was achieved in rats using the commercially popular Boletus edulis. Also confusing is that the Massart paper (2003), refers to the species by a synonym, Tricholoma auratum, and the abstract claims the paper describes "morphological characters that distinguish this species from the closely-related and edible T. equestre". I'll update this when I get a hold of the paper. Because the reported poisonings seem to be restricted to Europe, it is possible that a different but morphologically similar species may be the culprit. Another recent study (Niemenin et al., 2008) reports myo-, cardio- and hepatotoxic effects of T. equestre when consumed by mice for long periods of time. Obviously, prudence in deciding edibility should be exercised until further research is done.
See the Health Canada information before consuming this potentially dangerous mushroom.
Gluchoff K, Dangycay MP, Arpin N, Pourrat H, Regerat F, Topper E, Steglich W, Deruaz D, Lebreton P.
Chemotaxonomic research on fungi - 7,7'-biphysicon, bianthraquinone obtained from Tricholoma equestre L Per Fr (Basidiomycetes, Agaricales).
Comptes Rendus Hebdomadaires Des Seances De L Academie Des Sciences Serie D. 1972 274(11):1739-&.
Hata K, Sugawara F, Ohisa N, Takahashi S, Hori K.
Stimulative effects of (22E,24R)-ergosta-7,22-diene-3β,5α,6β-triol from fruiting bodies of Tricholoma auratum, on a mouse osteoblastic cell line, MC3T3-E1.
Biol Pharm Bull. 2002 25(8):1040-4.
Last modified: 01-Aug-2008