Pleurotaceae

Fan- or shell-shaped fungi growing in overlapping tiers on dead hardwood, with gills running down an off-centre stem or none at all. They are white-rot fungi — they break lignin down rather than leaving it — which makes them efficient decomposers and, commercially, the easiest medicinal mushrooms to cultivate. On straw, coffee grounds or sawdust they will fruit in weeks.

They are also, unusually for fungi, predators. Pleurotus species secrete droplets that paralyse nematodes, then grow hyphae into the immobilised worm and digest it — an adaptation to the nitrogen-poor wood they live on. It is one of the more startling facts in fungal biology and it is well documented.

The family’s clinical evidence is better than most of the medicinal mushrooms, and it is concentrated in one preparation. Pleuran, a β-(1,3/1,6)-D-glucan isolated from oyster mushroom, has been tested in randomised paediatric trials for recurrent respiratory infection — genuine controlled human data, not the in vitro immunology that carries most of this category.

The second thread is metabolic, and it has an unusual explanation. Pleurotus species contain lovastatin — the same molecule as the pharmaceutical statin — naturally, at variable concentrations. That gives the hypolipidemic effect reported for oyster mushroom a mechanism considerably more concrete than is usual for a food, though the content varies widely with strain and substrate and no oyster mushroom is a dose-controlled statin.

β-Glucans dominate, pleuran being the characterised example. The family is also a strong source of ergothioneine, the fungal-specific antioxidant amino acid, along with ergosterol and its UV-conversion product ergocalciferol (vitamin D2). Lovastatin is the family’s distinctive small molecule. Lectins and the pore-forming protein ostreolysin are present but are not part of any therapeutic use.