function add_menu_item_slug_class($classes, $item, $args) {

	$item_class = sanitize_title($item->title); // Convert title to a slug
	$classes[] = "menu-item-" . $item_class;

	return $classes;

}
add_filter('nav_menu_css_class', 'add_menu_item_slug_class', 1, 3);