Try the following code
string xml = @"<UDK>
<Gesture_0>Y + U</Gesture_0>
<Gesture_1>N + B + M</Gesture_1>
<Gesture_2>H + J</Gesture_2>
<Gesture_3>B + V + N</Gesture_3>
<Gesture_4>E + T</Gesture_4>
<Down>L</Down>
</UDK>";
XDocument document = XDocument.Parse(xml);
var result = document.XPathSelectElements(@"*/*").Select(e => e.Value).ToArray()