UVB 紫外光照射蘆薈（ALOE VERA）引發的光毒性   全文下載

UVB Photoirradiation of Aloe Vera – Formation of Free Radicals, Singlet Oxygen, Superoxide, and Induction of Lipid Peroxidation

蘆薈（Aloe vera）葉的提取物普遍用於商業用途。蘆薈所含有的化學物anthraquinones，經紫外光照射會產生活性氧（reactive oxygen species），而呈光毒性。所以商業用蘆薈己用活性碳將其去除。我們發現，這兩種蘆薈經UVB照射，都產生活性氧和自由基（carbon-centered free radicals）。然而，經過處理的蘆薈提取物，光毒性比沒處理過的更高。這現象和我們發表過用UVA照射這兩種蘆薈，產生的結果相似。所以用活性碳的處理，反而增強了蘆薈經紫外光照射，所產生的光毒性。

Aloe vera whole leaf extracts are incorporated into a wide variety of topically applied commercial products. Aloe vera whole leaf extracts contain anthraquinones, which can generate reactive oxygen species (ROS) upon UVA light irradiation. In this study, the phototoxicity of two Aloe vera whole leaf extracts, Aloe A and Aloe B, were examined. The Aloe B extract was prepared by treating the Aloe A extract with activated carbon (1%, wt/wt) and filtration to remove the Aloe latex components, including the anthraquinones. UVB irradiation of the Aloe vera whole leaf extracts induced lipid peroxidation in the presence of a lipid, methyl linoleate. The amounts of lipid peroxides formed were higher in the Aloe B, which contained lower amounts of anthraquinones than Aloe A. Sodium azide inhibited and deuterium oxide enhanced the formation of lipid peroxides by Aloe B, suggesting that singlet oxygen was involved in the mechanism. When superoxide dismutase was incorporated prior to irradiation, lipid peroxidation was inhibited, indicating that superoxide was produced during the photoirradiation of Aloe B. In addition, electron spin resonance (ESR) spectroscopy was also used to investigate the generation of free radicals by the UVB photoirradiated Aloe B. ESR measurements indicated that the UVB photoirra-diation of Aloe B produced carbon-centered free radicals. These results suggested that, as with the exposure to UVA light, the exposure of Aloe vera whole leaf extracts to UVB light can also generate ROS and induce lipid peroxidation.