植物エキスによる光過敏症防御効果の検討

抄録

Pheophorbide a is a catabolite of chlorophyll often found in food and supplements. Upon ingestion of pheophorbide a contained in food and subsequent exposure to sunlight, humans and animals can develop cutaneous photosensitivity. In search for photoprotective agents, we have first screened plant extracts using photo-oxidized hemolysis as an in vitro model for cutaneous photosensitivity. Thereafter, the photoprotective potential of the plant extracts was further tested in an animal model. Red blood cell suspensions from Wistar rats were exposed to visible light in the presence of pheophorbide a with or without the plant extracts. At the end of the light exposure, absorbance of the supernatants was measured and hemolysis ratios were calculated. For an animal test, the plant extracts or extraction solvent was given orally to female Wistar rats for one week prior to the light exposure. On the 8th day, after the pheophorbide a administration, the dorsal skin of rats was shaved and exposed to visual light to induce cutaneous photosensitivity. The dorsal skins were observed for redness, edema, and necrosis, and were also examined histologically. In hemolysis assays, the extract from Larix sibirica (Siberian larch) showed strong inhibitory activity. This extract was also shown to be effective in reducing the severity of the photosensitivity in rats. Furthermore, histological examination of the rats given Larix sibirica extract revealed that the inflammation remained mainly in epidermis and did not affect dermis.