Therapeutic Potential of Volatile Terpenes and Terpenoids from Forests for Inflammatory Diseases.

Forest trees are a major source of biogenic volatile organic compounds (BVOCs). Terpenes and terpenoids are known as the main BVOCs of forest aerosols. These compounds have been shown to display a broad range of biological activities in various human disease models, thus implying that forest aerosols containing these compounds may be related to beneficial effects of forest bathing. In this review, we surveyed studies analyzing BVOCs and selected the most abundant 23 terpenes and terpenoids emitted in forested areas of the Northern Hemisphere, which were reported to display anti-inflammatory activities. We categorized anti-inflammatory processes related to the functions of these compounds into six groups and summarized their molecular mechanisms of action. Finally, among the major 23 compounds, we examined the therapeutic potentials of 12 compounds known to be effective against respiratory inflammation, atopic dermatitis, arthritis, and neuroinflammation among various inflammatory diseases. In conclusion, the updated studies support the beneficial effects of forest aerosols and propose their potential use as chemopreventive and therapeutic agents for treating various inflammatory diseases.

Terpenes from Forests and Human Health.

Forest bathing has beneficial effects on human health via showering of forest aerosols as well as physical relaxation. Terpenes that consist of multiple isoprene units are the largest class of organic compounds produced by various plants, and one of the major components of forest aerosols. Traditionally, terpene-containing plant oil has been used to treat various diseases without knowing the exact functions or the mechanisms of action of the individual bioactive compounds. This review categorizes various terpenes easily obtained from forests according to their anti-inflammatory, anti-tumorigenic, or neuroprotective activities. Moreover, potential action mechanisms of the individual terpenes and their effects on such processes, which are described in various in vivo and in vitro systems, are discussed. In conclusion, the studies that show the biological effectiveness of terpenes support the benefits of forest bathing and propose a potential use of terpenes as chemotherapeutic agents for treating various human diseases.

In Vivo Screening of Traditional Medicinal Plants for Neuroprotective Activity against Aß42 Cytotoxicity by Using Drosophila Models of Alzheimer's Disease.

Alzheimer's disease (AD) is the most common neurodegenerative disorder, characterized by progressive neuronal loss with amyloid ß-peptide (Aß) plaques. Despite several drugs currently used to treat AD, their beneficial effects on AD progress remains under debate. Here, we established a rapid in vivo screening system using Drosophila AD models to assess the neuroprotective activities of medicinal plants that have been used in traditional Chinese medicine. Among 23 medicinal plants tested, the extracts from five plants, Coriandrum sativum, Nardostachys jatamansi, Polygonum multiflorum (P. multiflorum), Rehmannia glutinosa, and Sorbus commixta (S. commixta), showed protective effects against the Aß42 neurotoxicity. We further characterized the neuroprotective activity of ethanol extracts from P. multiflorum and S. commixta. Aß42-expressing flies that we used showed AD neurological phenotypes, such as decreased survival and motility and increased cell death and reactive oxygen species level. However, feeding these flies extracts from P. multiflorum or S. commixta showed strong suppression of such phenotypes. Similar results were observed in human cells, so that the treatment of P. multiflorum and S. commixta extracts increased the viability of Aß-treated SH-SY5Y cells. Moreover, 2,3,5,4'-tetrahydroxystilbene-2-O-ß-D-glucoside, one of the main constituents of P. multiflorum, also showed similar protective activity against Aß42 cytotoxicity in both Drosophila and human cells. Taken together, our results suggest that both P. multiflorum and S. commixta have therapeutic potential for the treatment of neurodegenerative diseases, such as AD.

Suppressive effects of SuHeXiang Wan on amyloid-ß42-induced extracellular signal-regulated kinase hyperactivation and glial cell proliferation in a transgenic Drosophila model of Alzheimer's disease.

SuHeXiang Wan (SHXW), a Chinese traditional medicine, has been used to treat infantile convulsions, seizures and strokes. Previously, we reported that modified SHXW, called KSOP1009, suppressed the hyper-activation of c-Jun N-terminal kinase (JNK) and Alzheimer's disease (AD)-like phenotypes in amyloid-ß42 (Aß42)-expressing Drosophila AD models. In the present study, we, further, investigated the detailed mechanism by which KSOP1009 suppresses the AD-like phenotypes of the model flies. As seen in the brains of AD patients, pan-neuronal expression of Aß42 in Drosophila increased activation of extracellular signal-regulated kinase (ERK), which was monitored by its phosphorylation level, and the number of glial cells in the brain. Suppression of caspase activity did not affect these phenomena, suggesting that Aß42 induces ERK activation and glial cell proliferation independently of apoptotic processes. KSOP1009 intake significantly reduced the level of ERK activation and the number of glial cells. Moreover, KSOP1009 intake also effectively decreased the defects in the wing vein formation induced by Epidermal growth factor receptor (Egfr) overexpression in fly wings, suggesting that it may contain an inhibitory substance that inhibits the EGFR/ERK signaling pathway. In addition, the Aß42-induced locomotive defect was partially rescued by inhibition of the elevated ERK activity through its antagonistic drug treatment. Taken together, these results suggest that KSOP1009 exerts its therapeutic effect by inhibiting the EGFR/ERK pathway and glial cell proliferation and by suppressing the JNK pathway and apoptosis.