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We present ESO - Very Large Telescope and ESA - Infrared Space Observatory 3to 4 $\mu$m spectra of Seyfert 2 nuclei as compared to our galactic centerlines of sight. The diffuse interstellar medium probed in both environmentsdisplays the characteristic 3.4 $\mu$m aliphatic CH stretch absorptions ofrefractory carbonaceous material. The profile of this absorption feature issimilar in all sources, indicating the CH$_2$/CH$_3$ ratios of the carbonchains present in the refractory components of the grains are the same inSeyfert 2 inner regions. At longer wavelengths the circumstellar contaminationof most of the galactic lines of sight precludes the identification of otherabsorption bands arising from the groups constitutive of the aliphatics seen at3.4 $\mu$m. The clearer continuum produced by the Seyfert 2 nuclei representspromising lines of sight to constrain the existence or absence of stronglyinfrared active chemical groups such as the carbonyl one, important tounderstand the role of oxygen insertion in interstellar grains. The SpitzerSpace Telescope spectrometer will soon allow one to investigate the importanceof aliphatics on a much larger extragalactic sample.Comment: 10 pages. Accepted for publication on April 30th 2004 in Astronomy  and Astrophysic

Organic matter in Seyfert 2 nuclei: Comparison with our Galactic center lines of sight