Capacitive reactance (Xc) is a measure of a capacitor's opposition to AC (alternating current). Just Like the Resistance.
When you come to contact with AC, the opposition to current for a human body must be the total impedance, considering your body capacitance and resistance.
Given by the Following Formulas.
According to this Link http://van.physics.illinois.edu/qa/listing.php?id=6793
The external human body resistance is about 1k to 100k Ohms, and the internal resistance is 300 to 1000 ohms. Only a thin layer of dry skin separates the internal resistance from an external object.
The human body capacitance to a far ground is 100-200pF, which is really a minimum value. Noting that the Capacitive reactance depend on the frequency.
So your overall body impedance will be quite significant because of the very small capacitance that produce a big Xc in the range of Mega Ohm. Helping to limit how much current can traverse your body.
But note that you only need to pass a current of (6 to 200 mA for 3 seconds) to make it fatal, and that's can happen when your body becomes sweaty decreasing your overall impedance.
So yes your Xc does play a role during electrocution, since its part of your body impedance which is the opposition to current.
All note that these parameters are not constant they vary from body to body.