How to create a rule that checks an extra profile field created with the core profile module?
With the limited info provided in your question, the best bet is that you cannot test for that extra field because you forgot to add a Rules Condition like &quot;entity has field&quot; (related to your profile_field1 field). So add that Rules Condition first (as your very first Rules Condition), and then try again.
For a video tutorial that illustrates the importance of this Entity has field condition, refer to Data types and data selection, especially what is shown between about 13:30 and 17:30 in it.
Update:
As per your updates to your question, I now understand that you're using the deprecated (core) profile module. This is a quote from its .info file:

; The Profile module is deprecated, and included in Drupal 7 for legacy
; purposes only. By default, the module will be hidden from the UI unless you
; are upgrading a site that uses the Profile module to extend user profiles.

Because of that, I doubt that there is a way to use the Rules module to check &quot;if the content of the 'profile_field1' doesn't match a certain regular expression&quot; (as in your question). Mostly because the Rules Condition like &quot;entity has field&quot; (=  typical prereq to configure these kinds of Rules Conditions) will not have any effect for such profile_field1-field. Maybe not the answer you would want to hear/read, but I'm afraid it explains that what you're asking for cannot be done with Rules.
Plan-b:
Give it some thought to consider switching to the Profile 2 module. Quote from its project page:

Designed to be the successor of the core profile module, which is deprecated for Drupal 7. In contrast to the deprecated module this module provides a new, fieldable 'profile' entity - leverage the power of fields!
Features
... Thanks to the foundational entity API the module integrates well with Rules ...

If you do, pretty sure my original answer (= add a Rules Condition like &quot;entity has field&quot;) will turn out to be the solution for what you try to achieve.