Trigger a custom function when option are saved in admin area

Here is the solution:

update_option_{option_name}: Runs after the option with name “option_name” has been updated. For example, for the option with name “foo”:

 add_action('update_option_foo', 'my_custom_function', 10, 2);

update_option: Runs before an option gets updated. Example:

add_action('update_option', 'my_custom_function', 10, 3);

updated_option: Runs after an an option has been updated. Example:

add_action('updated_option', 'my_custom_function', 10, 3);