Comparison of abundances of α-elements with literature data. Left panels: mean abundance ratios [Mg/Fe], [Si/Fe], [Ca/Fe], and [Ti/Fe]I (from top to bottom) as a function of metallicity from the homogeneous analysis of GCs in our FLAMES survey (filled blue points). Black filled circles are the average ratios in four metal-rich GCs from Muñoz and collaborators. The larger red point indicates NGC 6388 (present work). Grey and cyan open circles are field stars in the disc and bulge of the Milky Way, respectively, from different studies. References for all the data used in this figure are reported in Tables B.1 and B.2. Green filled squares are field stars in the dSph galaxies Fornax (Letarte et al. 2010; Lemasle et al. 2014) and Sagittarius (Minelli et al. 2021b). Right panels: enlargement around the metallicity of NGC 6388.