Sugi (Cryptomeria japonica) fragrance improved stress-induced memory impairment via decreasing stress hormone

Abstract The purpose of this study is to clarify the biological activity of the aromatic components of Sugi () essential oil on stress hormones. The effect of Sugi wood aroma on memory disorders was investigated in chronic corticosterone-treated (CORT) mice that were exposed to the aroma of Sugi wood essential oil (SEO), δ-cadinene, α-muurolene, and β-cadinene complex fraction (CDS) separated from SEO, and δ-cadinene for 28 days. The effect of SEO and the above fractions on improving memory impairment was assessed using a behavioral test in mice. To elucidate this mechanism, changes in CORT levels in the hippocampus after SEO inhalation were measured. SOE inhalation improved memory disorder in the novel object recognition and Barnes maze tests. Observation of Immunohistochemistry staining of brain tissues and mRNA quantification and production of brain-derived neurotrophic factor (BDNF) in the hippocampus revealed that the inhalation of SEO and CDS was effective in neuroprotection. Additionally, SEO inhalation promoted the discharge of injected hippocampal corticosterone, indicating suppression of neuronal cell damage in the hippocampus to improve stress-related memory disorder. To the best of our knowledge, this is the first report to demonstrate a decrease in stress hormone levels and identify the active components of SEO. The study also elucidated the mechanism of memory improvement effect of inhalation of SEO and suggested its potential as medical aromatherapy for the treatment of diseases of the brain and nervous system such as depression and dementia.