Anti-allergic action effect of Pseudolarix amabilis Rehd. extract and its efficacy on atopic dermatitis

Pseudolarix amabilis Rehd. extract was examined in vitro for antibacterial effects, anti-inflammatory effects, and inhibitory effects on histamine release. Pseudolarix amabilis Rehd. extract was also examined for efficacy on dermatitis in atopic dermatitis model mice (NC mice) and effects on keratinous moisture level and transepidermal water loss in miniature pigs. Pseudolarix amabilis Rehd. extract had antibacterial effects on Staphylococcus aureus, Candida albicans, and Streptococcus pyogenes; however this antibacterial effect varied with the temperature at which and conditions under which Pseudolarix amabilis Rehd. was extracted. Pseudolarix amabilis Rehd. extract at the final concentration of 2 mg/mL significantly inhibited the hyaluronidase activity; and at 0.005, 0.05, and 0.5 mg/mL, it also significantly inhibited the histamine release. In the mice in which atopic dermatitis had been induced, 28-day administration of Pseudolarix amabilis Rehd. extract at 4 and 400 mg/mL significantly inhibited aggravation of dermatitis without having effects on body weight. In the dorsal skin of miniature pigs, Pseudolarix amabilis Rehd. extract at 4 and 400 mg/mL significantly increased keratinous moisture level with the increase in the number of dosing days, and caused no changes in transepidermal water loss. From the above results, it is clear that Pseudolarix amabilis Rehd. extract inhibits both proliferation of bacteria and inflammation caused by antigens. Furthermore, it is suggested that Pseudolarix amabilis Rehd. extract will serve as a medicinal drug which effectively moistens the skin and prevents and heals dermatitis.