I think i found what was wrong.
tinyMCE automatically encode entities such:
< into <
> into >
" into "
& into &
I tried to use diferent types of entity_encoding on tinyMCE but none of them seems to work as i want, so i used PHP: html_entity_decode to decode tinyMCE text area and then i used htmlPurifier to sanitize the data and everything works ok now.
Hope someone else find this usefull.