First word with different style

First word with different style

Hello!!
I'm having problems with css styling. I'd like to set different style for the first word of a li element. The problem is, I can't add a tag to the html because is a prestashop site.... And, we are talking about the menu... (dynamic). So, my option is jQuery. I need something like :first-word but I don't understand what I've founded in the Internet. So, could it be possible something like:
  1. var Words = $('nav li').text();
  2. var FirstWord = Words.split(' '); //FirstWord[0]
  3. // and then I'd like to add a span to wrap the word
? Do you have any other idea?
Thank you!!!