Here is a useful table.
Exact figures vary from place to place.
If it an alcohol extract tincture and taken in realtively small amounts I would no think the fat content is the key factor.
Walnuts are very high in anti oxidants.
Walnuts are highish in omega sixes which should be taken into account in looking at intake.
I will try and find a chemical analysis.
RB
http://www.curezone.com/foods/fatspercent.asp
Looking after / buying your oil
http://www.artpurveyors.com/rancidity.html