SINGLET OXYGEN YIELDS, OPTICAL-PROPERTIES, AND PHOTOTOXICITY OF REDUCED DERIVATIVES OF THE PHOTOSENSITIZER CERCOSPORIN
SINGLET OXYGEN YIELDS, OPTICAL-PROPERTIES, AND PHOTOTOXICITY OF REDUCED DERIVATIVES OF THE PHOTOSENSITIZER CERCOSPORIN
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DOI：
10.1111/j.1751-1097.1992.tb04250.x
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发表时间：
1992-03-01
影响因子：
3.3
通讯作者：
DAUB, ME
中科院分区：
文献类型：
--
作者：
LEISMAN, GB;DAUB, ME
perylenequinone cercosporin （CR）是由Cercospora spp产生的单线态产氧光敏剂，在Cercospora spp寄生植物中起关键作用。一些证据表明，Cercospora spp对这种毒素的防御机制是产生一个细胞表面还原环境，导致CR的短暂还原。为了证明还原的CR毒性较小，合成了几种CR的衍生物。Hexaacetyl-dihydrocercosporin (HAC)是由还原乙酰化作用的CR。Noranhydrocercosporin (NAC)引起脱水的CR和tetramethyl-noranhydrodihydrocercosporin (TMNAC)还原NAC的甲基化的产物。过二烯丙二酮CR和NAC比它们各自的还原衍生物吸收更多的光，但荧光少得多；HAC、TMNAC和二硫代还原CR的相对荧光强度是CR和NAC的80 ~ 160倍。此外，CR和NAC在产生单线态氧方面效率更高。通过时间分辨红外发光测量，HAC、TMNAC和NAC的单线态氧量子产率相对于CR（调整为1.00）分别为0.16、0.19和0.73。用恒光抑制cr敏感真菌生长的方法测定其毒性。还原后的衍生物毒性低于它们各自的氧化形式。在黑暗条件下，这些化合物对任何一种真菌都没有明显的生长抑制作用，而在光照条件下，对抗cr真菌菊樱桃Cercospora kikuchi也没有明显的生长抑制作用。用亚麻酸甲酯进行的脂质过氧化实验也表明，HAC的活性低于CR。因此，CR的减少导致更大的荧光强度。单线态氧产量较低，光毒性较低。这些数据支持了一种假设，即瞬时的虫孢素减少是一种防御虫孢素毒性的机制。
The perylenequinone cercosporin (CR) is a singlet oxygen generating photosensitizer produced by Cercospora spp which plays a critical role in parasitism of plants by these fungi. Several lines of evidence suggest that the defense mechanism of Cercospora spp towards this toxin is the generation of a cell surface reducing environment that leads to transient reduction of CR. In order to demonstrate that reduced CR is less toxic, several derivatives of CR were synthesized. Hexaacetyl-dihydrocercosporin (HAC) was prepared by reductive acetylation of CR. Noranhydrocercosporin (NAC) resulted from dehydration of CR and tetramethyl-noranhydrodihydrocercosporin (TMNAC) was a product of reductive methylation of NAC. The perylenequinones, CR and NAC, absorb more light than their respective reduced derivatives, but are much less fluorescent; the relative fluorescence intensities of HAC, TMNAC, and dithionite-reduced CR were 80-160 times greater than that of CR and NAC. Also, CR and NAC were more efficient at generating singlet oxygen. As measured by time-resolved IR luminescence, the singlet oxygen quantum yields relative to CR (adjusted to 1.00) were 0.16, 0.19 and 0.73, respectively, for HAC, TMNAC, and NAC. Toxicity was measured by assaying for inhibition of growth of CR-sensitive fungi in constant light. The reduced derivatives were less toxic than their respective oxidized forms. None of the compounds showed significant growth inhibition in the dark with any of the fungi, or when assayed in the light with the CR-resistant fungus Cercospora kikuchii. A lipid peroxidation assay with methyl linolenate also showed that HAC was less active than CR. Thus, reduction of CR leads to greater fluorescence intensities. lower production of singlet oxygen and lower phototoxicity. These data support the hypothesis of transient cercosporin reduction as a mechanism of defense against cercosporin toxicity.