We present observations of 11 high redshift quasars (3.9 \ z \ 5.0) with low spectral resolution in the restframe ultraviolet using 1 at the VLT UT 1. emission-line fluxes of strong permitted intercombination ultraviolet emission lines measured to estimate the chemical composition of the line emitting gas. to photoionization calculations indicate gas metallicities in broad emission line region in the range of solar to several times solar. average of the mean metallicity of each high-z quasar in this sample is Z/Z_\ = 4.3 \± 0.3. a chemical evolution time scale of \τ_\ evol \ 0.5 - 0.8 Gyrs, we derive a redshift of \ f \ 6 ~\ to~ 8 for the onset of the first major star formation (H₀ = 65 km s-1 Mpc-1, \Ω \ M = 0.3, \Ω _\Λ = 0.7), corresponding to an age of the universe of 108 yrs at this epoch. note that this epoch is also supposed to be the era of re-ionization the universe.