To survive in harsh environments, phyllosphere microorganisms have developed numerous adaptive strategies against stressors. One such strategy is the synthesis of compounds that absorb ultraviolet A radiation (UVA). The chemical structure of a UVA-absorbing compound from Methylobacterium sp. strain W-213 was elucidated by spectroscopic analyses. 1H, 13C, and two-dimensional nuclear magnetic resonance spectra indicated the presence of N -methyl-α-galactosamine. The entire structure was revealed by interpretation of INADEQUATE and high-resolution liquid chromatography/electrospray ionization mass spectra. The absolute configuration was established by X-ray analysis and the compound was identified as 2-{(4a R, 6 R, 7 R, 8 R, 8a R)-7,8-dihydroxy-6-hydroxymethyl-1,2-dimethyl-4a H, 6 H, 7 H, 8 H, 8a H -pyrano[2,3- b][1,4]oxazin-3-yl}-2-iminoacetic acid and named ‘methylobamine'. Methylobamine shows promise for pharmaceutical and cosmetic applications due to its high polarity, UVA absorption properties, and stability under UVA exposure.
Extraction methods for measuring blue fluorescence generated in rat liver and brain in situ were examined. Great care should be taken when the traditional chloroform/methanol extraction method is employed because artificial blue fluorescence is readily produced by subsequent light irradiation, or by passage through a silicic acid column. In contrast, sodium dodecylsulfate (SDS) extraction were found to be suitable since no artificial blue fluorescence was produced by subsequent light irradiation. The levels of blue fluorescence in rat tissues were re-evaluated following SDS extraction. The levels of blue fluorescence in rat liver increased with age, whereas those in rat brain did not. Accumulation of blue fluorescence in the tissues was only slightly enhanced by vitamin E-deficiency. Blue fluorescence in the extracts did not seem to be derived from autofluorescent yellow lipofuscin in situ. The results were not always consistent with earlier observations obtained using the chloroform/methanol extraction.
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