Phenolic changes in a combined herbal extract of Lithospermum erythrorhizon, Houttuynia cordata, and Spirodela polyrhiza and alleviation of DNCB-induced atopic dermatitis in BALB/c mice

Atopic dermatitis (AD) is an inflammatory skin disease showing skin barrier dysfunction, eczematous lesions, severe itching, and abnormal immune responses. The aim of this study was to determine whether an herb combination of Lithospermum erythrorhizon (LE), Houttuynia cordata (HC), and Spirodela polyrhiza (SP) has a superior anti-AD effect. Forty-two compounds were identified in LE, HC, SP, and a combined herb extract of LE, HC, and SP (LHS) using ultra-high-pressure liquid chromatography (UHPLC)-Orbitrap mass spectrometer (MS). The concentration of flavonoid glycosides including orientin (luteolin-8- C -glucoside), quercetin-3- O -rhamnoside, and luteolin-7- O -glucoside in the LHS was increased than in individual extracts. Furthermore, the treatment of LHS most effectively inhibited the increase of epidermal thickness, the number of mast cells, and the release of immunoglobulin E compared with that with each extract. These results suggest that the potential anti-AD effects of the LHS are due to the changes of bioactive compounds by the combination of herbs. Graphical abstract