Well judging from the provided XML content it seems that you want to retrieve the <li> element's last presented inner text.
In that case you can use the following:
foreach (HtmlNode l in liContent)
for (int i = l.ChildNodes.Count - 1; i >= 0; i--)
{
string lastInnerText = l.ChildNodes[i].InnerText.Trim();
if (!string.IsNullOrEmpty(lastInnerText))
{
Console.WriteLine("InnerText: " + lastInnerText);
break;
}
}