<?php if (is_single() ) {
if (have_posts()) : while (have_posts()) : the_post();
$strDescr = wp_trim_words(get_the_content(), 30, '');
$strDescr = preg_split("/[*] /", $strDescr);
echo '<meta name="description" content="'.$strDescr[0].$strDescr[1].$strDescr[2].$strDescr[3].'" >';
endwhile; endif; }
?>