Thelephoric acid

Alzheimer's disease (AD), a major neurodegenerative disorder, is associated with the enzymatic reaction of β-secretase (BACE1) on the amyloid precursor protein (APP) for the generation of neurotoxic amyloid-β (Aβ). Therefore, Aβ accumulation and oxidative stress-induced neuronal cell death are the pathogenic hallmarks of AD. In this study, we tried to identify BACE1 inhibitors and neuroprotectants from natural products, in particular, from the Korean mushroom Polyozellus multiplex. Four p-terphenyls were identified from the ethanolic extract of P. multiplex; polyozellin (1), thelephoric acid (2), polyozellic acid (3), and kynapcin-12 (4). Compounds 1-4 effectively inhibited BACE1 activity with a half-maximal inhibitory concentration (IC50) of 3.08, 3.50, 4.78, and 15.79 μM, respectively. Compounds 1-3 reduced the production of neurotoxic Aβ1-42 production in APPswe-N2a cells in a concentration-dependent manner. When HT22 cells were stressed with 5 mM glutamate, compounds 2 and 3 significantly recovered cell viability. It was correlated with their inhibitory properties against glutamate-mediated Ca(2+) influx, intracellular reactive oxygen species (ROS) generation, lipid peroxidation, reduction in Bcl-2 and Bid levels, and enhanced phosphorylation of mitogen-activated protein kinase (MAPK). Thus, P. multiplex and the isolated p-terphenyls might be useful in the development of lead compounds for the prevention of neurodegenerative diseases, especially AD.

Thelephoric acid is an antioxidant produced by the hydrolysis of polyozellin, which is isolated from Polyozellus multiplex. In the present study, the inhibitory effects of polyozellin and thelephoric acid on 9 cytochrome P450 (CYP) family members (CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4) were examined in pooled human liver microsomes (HLMs) using a cocktail probe assay. Polyozellin exhibited weak inhibitory effects on the activities of all 9 CYPs examined, whereas thelephoric acid exhibited dose- and time-dependent inhibition of all 9 CYP isoforms (IC50 values, 3.2-33.7 μM). Dixon plots of CYP inhibition indicated that thelephoric acid was a competitive inhibitor of CYP1A2 and CYP3A4. In contrast, thelephoric acid was a noncompetitive inhibitor of CYP2D6. Our findings indicate that thelephoric acid may be a novel, non-specific CYP inhibitor, suggesting that it could replace SKF-525A in inhibitory studies designed to investigate the effects of CYP enzymes on the metabolism of given compounds.

One novel p-terphenyl compound, polyozellic acid (1), and its acetone adduct (3), along with a known p-terphenyl compound, thelephoric acid (2), were isolated from the mushroom Polyozellus multiplex. Their molecular structures were determined by spectroscopic analysis, X-ray crystallographic analysis, and chemical modification. In some assays related to angiogenesis, compounds 1 and 2 in particular showed inhibitory effects on proliferation, tubule formation, and invasion of human umbilical vein endothelial cells. The quinone moiety within these molecules possibly contributes to their antiangiogenesis activity.