Chaga (Inonotus obliquus) and Cognitive function: evidence and sources

Oxidative stress is implicated in the pathogenesis of various neurodegenerative diseases including Parkinson's disease (PD). 3,4-Dihydroxybenzalacetone (DBL) is a small catechol-containing compound isolated from Chaga (Inonotus obliquus [persoon] Pilat), and has been reported to have beneficial bioactivities, including antioxidative, anti-inflammatory, and anti-tumorigenic activities, with a relatively low toxicity to normal cells. We, therefore, investigated the neuroprotective activity of DBL against the PD-related neurotoxin 6-hydroxydopamine (6-OHDA). Pretreatment of human neuroblastoma SH-SY5Y cells with DBL, but not with another Chaga-derived catechol-containing compound, caffeic acid, dose-dependently improved the survival of 6-OHDA-treated cells. Although DBL did not reduce 6-OHDA-induced reactive oxygen species in the cell-free system, it promoted the translocation of Nrf2 to the nucleus, activated the transcription of Nrf2-dependent antioxidative genes, and increased glutathione synthesis in the cells. Buthionine sulfoximine, an inhibitor of glutathione synthesis, but not Sn-mesoporphyrin IX, a heme oxygenase-1 inhibitor, or dicoumarol, an NAD(P)H: quinone oxidoreductase 1 inhibitor, abolished the protective effect of DBL against 6-OHDA. Furthermore, DBL activated stress-associated kinases such as Akt, ERK, and p38 MAPK, and PI3K or Akt inhibitors, but not ERK, p38, or JNK inhibitors, diminished DBL-induced glutathione synthesis and protection against 6-OHDA. These results suggest that DBL activates the Nrf2/glutathione pathway through PI3K/Akt, and improves survival of SH-SY5Y cells against 6-OHDA toxicity.

The present study was aimed to investigate the cognitive enhancing and anti-oxidant activities of Inonotus obliquus (Chaga) against scopolamine-induced experimental amnesia. Methanolic extract of Chaga (MEC) at 50 and 100 mg kg (-1)doses were administered orally for 7 days to amnesic mice. Learning and memory was assessed by passive avoidance task (PAT) and Morris water maze (MWM) test. Tacrine (THA, 10 mg kg (-1), orally (p.o)) used as a reference drug. To elucidate the mechanism of the cognitive enhancing activity of MEC, the activities of acetylcholinesterase (AChE), anti-oxidant enzymes, the levels of acetylcholine (ACh) and nitrite of mice brain homogenates were evaluated. MEC treatment for 7 days significantly improved the learning and memory as measured by PAT and MWM paradigms. Further, MEC significantly reduced the oxidative-nitritive stress, as evidenced by a decrease in malondialdehyde and nitrite levels and restored the glutathione and superoxide dismutase levels in a dose dependent manner. In addition, MEC treatment significantly decreased the AChE activity in both the salt and detergent-soluble fraction of brain homogenates. Further, treatment with MEC restored the levels of ACh as did THA. Thus, the significant cognitive enhancement observed in mice after MEC administration is closely related to higher brain anti-oxidant properties and inhibition of AChE activity. These findings stress the critical impact of Chaga, a medicinal mushroom, on the higher brain functions like learning and memory.