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One of predominant hallmarks in Alzheimer’s disease (AD) is extracellular senile plaques containing β-amyloid peptide (Aβ). Aβ is known to be directly responsible for the free radical production and lipid peroxidation, leading to apoptosis and cellular death. In this study, we investigated the possible protective effect of kaempferol 3-O-(6''-acetyl)-β-glucopyranoside (KAG) isolated from butterbur (Petasites japonicus) leaves against Aβ-induced neurotoxicity. Exposure of mouse neuroblastoma B103 cells to Aβ(25-35) at the concentration of 50 μM significantly reduced cellular viability and increased both oxidative stress and apoptotic rate. However, pretreatment of B103 cell with isolated KAG at 10 μM significantly inhibited Aβ-induced apoptotic cellular damage and reactive oxygen species (ROS) generation. Pretreatment of KAG also completely inhibited caspase-3 activity to the basal level at the concentration of 10 mM. This study therefore demonstrated that Aβ induced cellular death might be prevented by KAG from butterbur leaves by the suppression of ROS and the subsequent recovery of apoptotic cell death.
From the 48 hour-cultured mycelial broth of Phellinus linteus, six compounds were isolated by means of ethyl acetate extraction silica gel column chromatography and preparative thin layer chromatography, consecutively. Compound 1 was identified as a succinic acid by the comparison of its spectral data with authentic sample. Compounds 2 and 3 were identified as p-hydroxyphenyl acetic acid methyl ester and p-hydroxybenzaldehyde by spectroscopic studies, respectively. NMR and MS studies of compound 6 revealed that it was 2,5-dihydroxymethyl furan. Compound 4, which showed similar NMR absorptions and MS fragmentation pattern with those of compound 6 was identified as 2-hydroxymethyl-5-methoxymethylfuran. These structures were verified by the spectral data of the acetate derivatives of the compounds. Compound 5 was supposed to be a N-acetyltyramine from its ¹H-NMR and EI-MS data, and its structure was confirmed by a synthesis starting from tyramine.
Four minor compounds were isolated from fruiting bodies of Polyozellus multiflex by consecutive chromatographic separation. Their structures were identified as ergost-4,6,8,22-tetraen-3-one, 4-methoxy-6-methyl-2H-pyran-2-one, p-anisic acid, and p-hydroxybenzoic acid by spectral analysis. They could not inhibit prolyl endopeptidase nor acetylcholine esterase at the concentration up to 100 ppm.