Diterpene para-hydroquinone compounds derived from cryptoquinone inhibit adipocyte differentiation of mouse 3T3-L1 cells and activate the Nrf2/ARE pathway

Cytotoxic Natural Products from Cryptomeria japonica (Thunb. ex L.) D.Don

Cryptomeria japonica is a commercially important tree native to Japan. The tree belongs to the ancient genus Cryptomeria and has found important uses as a medicinal plant, as well as a main source of timber in Japan. In recent years, there has been an increased interest in discovering extended uses of C. japonica as a source of novel bioactive natural products with potential applications as lead compounds for active principles of future drugs. The compounds were isolated by a combination of two-phase extraction, XAD-7 Amberlite column chromatography, Sephadex LH-20 column chromatography and preparative High Performance Liquid Chromatography (HPLC). The structures were determined by a combination of several 1D and 2D Nuclear Magnetic Resonance (NMR) experiments and high-resolution mass spectrometry. Here, we report on the isolation and characterization of the novel biflavone glucoside hinokiflavone 7″-O-β-glucopyranoside, in addition to sixteen known compounds including the flavonols quercetin, quercetin 3-O-α-rhamnopyranoside and quercetin 3-O-β-galactopyranoside, the dihydroflavonols taxifolin 3-O-β-glucopyranoside, taxifolin 7-O-β-glucopyranoside, the flavanones naringenin, naringenin 7-O-β-galactopyranoside and eriodictyol 4'-O-β-glucopyranoside, the flavanol catechin, the biflavonoid amentoflavone, the dihydrochalcone phloretin 2'-O-β-glucopyranoside, the sesquiterpenoid roseoside, the polyphenolic compounds chlorogenic acid, methyl chlorogenate and the flavanocoumarins catechin-(7,8)-7″-(3,4 dihydroxyphenyl)-dihydro-8″(3H)-pyranone, and mururin A. The compounds exhibited low-to-moderate cytotoxic activity against MOLM-13 leukemia cells.

Nrf2 and HSF-1 Pathway Activation via Hydroquinone-Based Proelectrophilic Small Molecules is Regulated by Electrochemical Oxidation Potential

Activation of the Kelch-like ECH-associated protein 1/nuclear factor (erythroid-derived 2)-like 2 and heat-shock protein 90/heat-shock factor-1 signal-transduction pathways plays a central role in combatting cellular oxidative damage and related endoplasmic reticulum stress. Electrophilic compounds have been shown to be activators of these transcription-mediated responses through S-alkylation of specific regulatory proteins. Previously, we reported that a prototype compound (D1, a small molecule representing a proelectrophilic, para-hydroquinone species) exhibited neuroprotective action by activating both of these pathways. We hypothesized that the para-hydroquinone moiety was critical for this activation because it enhanced transcription of these neuroprotective pathways to a greater degree than that of the corresponding ortho-hydroquinone isomer. This notion was based on the differential oxidation potentials of the isomers for the transformation of the hydroquinone to the active, electrophilic quinone species. Here, to further test this hypothesis, we synthesized a pair of para- and ortho-hydroquinone-based proelectrophilic compounds and measured their redox potentials using analytical cyclic voltammetry. The redox potential was then compared with functional biological activity, and the para-hydroquinones demonstrated a superior neuroprotective profile.