Problem with change the Abstract name

I use the next enviroment for the abstract section:

newcommand{abstractname}{Prefacio}  
makeatletter
if@titlepage
  newenvironment{abstract}{%
      titlepage
      nullvfil
      @beginparpenalty@lowpenalty
      begin{flushleft}%
        noindent bfseries Huge abstractname
        @endparpenalty@M
      end{flushleft}}%
     {parvfilnullendtitlepage}
else
  newenvironment{abstract}{%
      if@twocolumn
        section*{abstractname}%
      else
        small
        begin{center}%
          {bfseries abstractnamevspace{-.5em}vspace{z@}}%
        end{center}%
        quotation
      fi}
      {if@twocolumnelseendquotationfi}
fi
makeatother 

But still put "Abstract" in the output. I’m working with documentclass type book.