Methylobamine, a UVA-absorbing compound from the plant-associated bacteria methylobacterium sp.

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-((4aR,6R,7R,8R,8aR)-7,8-dihydroxy-6-hydroxymethyl-1,2-dimethyl-4aH,6H,7H,8H,8aH-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.