I solved with XSLT extensions:

///<summary>

/// XSLT extensions, referenced from /config/xsltExtensions.config:

///   <ext assembly="/bin/MyAssembly" type="MyTypeName" alias="MyExtensions"/>

///</summary>

public class MyExtensions

{

    private static Regex MacroExpression = new Regex("<?umbraco_macro (.*?)/>",

        RegexOptions.Singleline | RegexOptions.IgnoreCase);

    private static Regex PropertyExpression = new Regex("(\\S*?)=\"(.*?)\"",

        RegexOptions.Singleline | RegexOptions.IgnoreCase);

    public XPathNodeIterator DecodeMacroReferences(string input)

    {

        var doc = new XDocument();

        var macros = new XElement("macros");

        doc.Add(macros);

        foreach (Match match in MacroExpression.Matches(input))

        {

            var macro = new XElement("macro");

            foreach (Match propMatch in PropertyExpression.Matches(match.Groups[1].Value))

            {

                macro.Add(new XAttribute(propMatch.Groups[1].Value, propMatch.Groups[2].Value));

            }

            macros.Add(macro);

        }

        return doc.CreateNavigator().Select("/");

    }

}

found at: http://www.rightpoint.com/community/blogs/viewpoint/archive/2010/09/29/treating-umbraco-macro-references-as-data.aspx

that has transformed the xml generated by the macro container:

<macros>

<macro macroalias="SlideShowHomeItem" linkArticolo="1078" imgAlternativa="" titleAlternativo="" />

<macro macroalias="SlideShowHomeItem" linkArticolo="1079" imgAlternativa="" titleAlternativo="" />

</macros>

Now I can access the properties of each element with a simple loop:

<xsl:variable name="macroSlideShow" select="$currentPage/slideShow" /><!--Alias Macro Container in Document Types-->

 <xsl:for-each select="msxml:node-set(Ext.ItemMacroContainer:DecodeMacroReferences($macroSlideShow))/macros/child::*">
    <xsl:variable name="currentNode" select="."/>
    <textarea>
      <xsl:value-of select="$currentNode/@linkArticolo"/>
    </textarea>
  </xsl:for-each> 

Happy to have solved, I was about to leave.

Umbraco v 4.7.1.1

If there is a better solution let me know :-)