Use wp_trim_words()
wp_trim_words( get_the_content(), 20 )
As you’re outside the main loop
wp_trim_words( $recent[ 'post_content' ], 20 )
If you want to apply the same filters as to the_content() in the main loop
wp_trim_words( apply_filters( 'the_content', $recent[ 'post_content' ] ), 20 )