Polyozellus multiplex

Craterellus cornucopioides, a lookalike species

The spores are roughly spherical to broadly ellipsoid in shape, covered with small wart-like projections (tubercules), and have dimensions of 6–8.5 by 5.5–8 µm.[11] Viewed microscopically, they are hyaline, meaning they appear translucent or colorless. Chemical tests may also be used to help distinguish the spores: in the presence of potassium hydroxide (KOH), the spores turn slightly green; the spores are not amyloid, meaning they do not take iodine when treated with Melzer's reagent; and the spores are acyanophilous, meaning they do not readily absorb methyl blue stain. The cystidia that comprise the hymenium are filamentous and 3–4 µm wide by 28–40 µm long. The outer tissue layer of the cap—the cuticle, or pileipellis—is made of interwoven hyphae, and stains olive-green in KOH. Clamp connections are present, but not at all the cell partitions.[12] The basidia, the spore-bearing cells, are 32–38 by 5–6 µm and four-spored.[5]

The horn-of-plenty mushroom (Craterellus cornucopioides) also has a blackish fruit body and a smooth hymenium, but is distinguished from P. multiplex by its thin flesh, a trumpet- or tubular-shaped fruit body (rather than fan- or spoon-shaped), and grey to black colors. A closely related species, the fragrant chanterelle (Cantharellus odoratus), also tends to grow in dense clusters, but it is orange rather than blue.[13] Craterellus caeruleofuscus does not form compound clusters, and is not restricted to coniferous forests. The pig's ear Gomphus, species Gomphus clavatus, is similar in shape and form but fleshier, and light violet to pink.[14]

Other species of Polyozellus are easy to mistake for P. multiplex, as prior to 2018, the genus was thought to be composed of only one species, but is now split into 5 species.[2] Species are mainly distinguished by location, with P. multiplex only being confirmed on the Eastern coast.[2] Other species like P. astrolazulinus, P. mariae, and P. marimargaretae have also been identified on the East coast and therefore identification may be more difficult in regions of overlap.

Polyozellus multiplex is edible,[23] and is collected for sale in Asian countries such as Korea, Japan, and China.[20] In North America, it is sometimes collected recreationally[24] and commercially.[25] The taste is described as mild, and the odor as mild or aromatic.[26] Mycologist David Arora claims the flavor to be inferior to Craterellus. It can be prepared by cooking.[27] Fruit bodies may be preserved by drying.[28]

Skeletal formula of polyozellin

The compound polyozellin—a chemical which can be isolated and purified from P. multiplex—inhibits prolyl endopeptidase (PEP), an enzyme that has a role in processing proteins (specifically, amyloid precursor protein) in Alzheimer's disease. Chemicals that inhibit PEP have attracted research interest due to their potential therapeutic effects.[29] Further analyses of extracts from P. multiplex revealed similar dibenzofuranyl derivatives of polyozellin, each with different chemical properties, including kynapcin-12,[30] kynapcin-13 and -28,[31] and -24.[32] A total synthesis of kynapcin-24 was achieved in 2009.[33]

Research conducted in 2003 suggests that extracts from P. multiplex may have suppressive effects on stomach cancer.[20][34] The study showed that feeding a low concentration (0.5% or 1%) of the mushroom extract enhanced the activities of the enzymes glutathione S-transferase and superoxide dismutase, and increased the abundance of the molecule glutathione. The extract also augmented the expression of the protein p53. All of these substances protect the human organism against cancer.[20] Additional studies reported in 2004 and 2006 attribute anti-tumor properties to polyozellin.[35][36]