Victoria University of Wellington, Wellington, New Zealand.
Photochem Photobiol. 2011 Jan-Feb;87(1):45-50. doi: 10.1111/j.1751-1097.2010.00827.x.
The genus Phormium (New Zealand flax) has fiber possessing a high content of lignin and, like other lignocellulosic materials, it is subject to photodegradation. Photoproducts in the fiber absorbing over a broad spectral region from ∼370 to 600nm are observed as a result of exposure to near-UV radiation from 350 to 400 nm. Irradiation was shown to produce hydrogen peroxide and this can account, at least in part, for the photo-oxidation manifested in changes in the reflectance spectra of the fibers. Unirradiated solid fibers and their aqueous extracts exhibit fluorescence with excitation maxima at 350-360nm and emission maxima at 440 nm. The fluorescence spectra of the fibers change following exposure to near-UV radiation with the major fluorophore being substantially photodegraded, evidenced by a substantial loss of emission between 410 and 480nm, which is largely responsible for the yellow and duller appearance of the fiber. Analysis of the aqueous extracts of the fibers, using electron-spray ionization mass spectroscopy of aqueous extracts, showed the presence of coumarin, hydroxycoumarin and a number of substituted hydroxycoumarins. The spectral distributions of the fluorescence associated with the unirradiated fibers and their aqueous extracts are consistent with them originating from a number of 7-hydroxycoumarins present.
植物属 Phormium（新西兰亚麻）的纤维含有高含量的木质素，与其他木质纤维素材料一样，它容易光降解。在 350nm 至 400nm 的近紫外辐射下，纤维吸收的光谱范围从约 370nm 到 600nm 的光产物被观察到。辐照被证明会产生过氧化氢，这至少可以部分解释纤维反射率光谱中表现出的光氧化变化。未辐照的固体纤维及其水提物具有激发最大值在 350-360nm 和发射最大值在 440nm 的荧光。纤维的荧光光谱在暴露于近紫外辐射后发生变化，主要荧光团被大量光降解，这表现为在 410nm 至 480nm 之间的发射大量损失，这主要导致纤维变黄和变暗。对纤维的水提物进行电子喷雾电离质谱分析，表明存在香豆素、羟基香豆素和一些取代的羟基香豆素。与未辐照纤维及其水提物相关的荧光的光谱分布与其源自存在的几种 7-羟基香豆素一致。
