  The 2175 {\AA} ultraviolet (UV) extinction bump in interstellar medium (ISM)
of the Milky Way was discovered in 1965. After intensive exploration of more
than a half century, however, its exact origin still remains a big conundrum
that is being debated. Here we propose a mixture model by which the extinction
bump in ISM is argued possibly relevant to the clusters of hydrogenated
T-carbon (HTC) molecules (C40H16) that have intrinsically a sharp absorption
peak at the wavelength 2175 {\AA}. By linearly combining the calculated
absorption spectra of HTC mixtures, graphite, MgSiO3 and Fe2SiO4, we show that
the UV extinction curves of optional six stars can be nicely fitted. This
present work poses an alternative explanation toward understanding the physical
origin of the 2175 {\AA} extinction bump in ISM of the Milky Way.
