Constituents

Lentinan (polysaccharide), eritadenine (purine alkaloid), ergocalciferol, ergothioneine, vitamins (B1, B2, B12, C and E), lignin and chitin

 

Pharmacology

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The majority of research regarding shiitake has explored a specific ß-D-glucan, lentinan. Lentinan, like other ß-D-glucans, has immune-centric qualities and supports a healthy response to inflammation.

 

Immune-regulating Lentinan inhibits both tumor angiogenesis and the growth of lung and colon cancers by increasing IFN-γ production, and exerts antitumor effects in colon cancer cells both in vitro and in vivo (1).  Cancer cell apoptosis is induced through two major pathways: the intrinsic pathway, via overproduction of reactive oxygen species, and activation of caspase-9, and the extrinsic pathway, through the increase of TNF- α, NF-kB inhibition, and activation of caspase-8 and 3 (2). Other studies have concluded that lentinan also inhibits tumor cell proliferation through targeting the p53 tumor suppressor gene, increasing tumor cell apoptosis through caspase-3-dependent signaling pathways, and inhibiting angiogenesis through VEGF depression (3).

 

Anti-inflammatory NF-κB is an important regulatory element for IL-8 expression in human epithelial cells; in an animal study, lentinan suppressed IL-8 gene expression, indicating that lentinan could be beneficial for states of intestinal inflammation in humans (4). 

 

Oral antimicrobial In vitro studies have explored the effect of shiitake extracts containing adenine and oxalic acid on common bacteria implicated in caries and gingivitis. Adenine showed 50% biofilm inhibition with Streptococcus mutans, and 20% biofilm disaggregation, while oxalic acid showed biofilm inhibition of 80% for Actinomyces naeslundii (5,6). The shiitake mushroom aqueous extract (1 mg/ml) demonstrated antimicrobial activity against 84.6% of 39 microorganisms tested (7). Sesquiterpenes, steroids, anthraquinone, benzoic acid derivatives and quinolones in shiitake extract all inhibit growth of S. mutans. Oil extract is the most efficacious in biofilm inhibition and disruption, potentially due to the carvicrol content in the oil extract, which significantly inhibited and disrupted P. gingivalis (8).

 

Current and traditional medicinal use

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History and folk use

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The legend goes that 5,000 years ago a deity, Shennong, bestowed the world with shiitake as well as all other medicinal mushrooms. Logs would be inoculated with shiitake spores during a child’s birth, and the child and the mushrooms would mature together until adulthood. At adulthood, the child would be lucky enough to inherit the fortune of the shiitake flush.

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Current research

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Antineoplastic

Patients with immune dysregulation of the stomach were administered either chemotherapy alone or chemo-immunotherapy with lentinan. There was a significantly longer median overall survival time in the lentinan group, and concluded that lentinan should be widely accepted for use as adjunctive chemo-immunotherapy treatment for advanced dysregulation. The lentinan treated group was administered 2mg/body via IV for 30 minutes every two to three weeks (9). Lentinan provides synergistic actions with a molecular targeting agent and cytotoxic drugs through the modulation of antibody-dependent cellular toxicity and programmed cell death, which may support the idea that the chemo-immunotherapy prolongs the survival of advanced immune dysregulation of the stomach, compared to chemotherapy alone (10).

 

Other studies exploring the use of lentinan as an adjunct to chemotherapy found less adverse side effects from the chemotherapy, improved IFN-γ production, and increased NK cell count (11,12).

 

Immune-modulating

Healthy young adults who ate 5-10g of dried shiitake mushrooms daily for four weeks had increased proliferation of antiviral immune cells, decreased inflammation markers, and increased immune-modulating cytokines (13).

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Pharmacy

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Double extraction. 1:1 - 1:5 liquid extract. The mushroom has been extracted with both water and alcohol.

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Hot aqueous extract. Mushroom has been boiled for multiple hours either as a tea or used as a broth.

 

Powdered extract. 1:1 - 10:1. May be extracted only with water or with both water and alcohol. The extract is then dehydrated into a powdered extract. 10:1 implies that every 1g of extract is equivalent to 10g of dried mushroom.

 

Myceliated grain. Mycelium is grown on grain substrate and when the mycelium seems to have digested the majority of the grain, the entire block is extracted.