Akiyo Kameyama

Improvement of hypertension and vascular dysfunction by hydroxyhydroquinone-free coffee in a genetic model of hypertension

Chlorogenic acid, a polyphenol found in coffee, has antihypertensive actions, but epidemiologic data on the effects of coffee on blood pressure are controversial. Specific coffee components that inhibit the hypotensive effect of chlorogenic acid and the physiologic mechanisms underlying the effects of coffee without these components were investigated. One component, hydroxyhydroquinone (HHQ), inhibited the hypotensive effects of chlorogenic acid in spontaneously hypertensive rats (SHR). The attenuation of hypertension by HHQ‐free coffee was associated with nitric oxide, the suppression of mRNA expression of NAD(P)H oxidase, and the improvement in endothelium‐dependent vasodilation in the aorta. Thus, HHQ‐free coffee might regulate vascular tone by improving the bioavailability of nitric oxide in SHR.

Isolation and structural determination of spilacleosides A and B having a novel 1,3-dioxolan-4-one ring

Abstract As the first natural product incorporating 1,3-dioxolan-4-one in spiro structure, spilacleosides A and B were isolated from Ruscus aculeatus , and the absolute structures determined.

The inhibitory effect of a Platycodon root extract on ultraviolet B-induced pigmentation due to a decrease in Kit expression

The signaling of stem cell factor (SCF) through its receptor Kit is known to play an important role in regulating cutaneous melanogenesis. In the course of UVB-induced pigmentation, the expression of membrane-bound SCF by epidermal keratinocytes is upregulated at an early phase and subsequently activates neighboring melanocytes via their Kit receptors. In order to identify effective skin-lightening materials, we screened botanical extracts to determine their abilities to diminish Kit expression in melanocytes. A Platycodon root extract was consequently found to have a remarkable inhibitory activity on Kit expression. When the extract was applied to three-dimensional human skin substitutes in vitro and to human skin in vivo after UVB irradiation, their pigmentation was significantly reduced, confirming the substantial contribution of the suppression of SCF/Kit signaling to preventing or inhibiting melanin synthesis. These data demonstrate that a Platycodon root extract is a promising material for a skin-lightening product to improve pigmentation-related diseases.