Well with the kavalactone basic structure there are three oxygens on one ring of the molecule and varying substituents on the other ring, so I would say kavalactones are more polar than nonpolar.
The kavalactones 'shouldnt' be soluble in the nonpolar naptha, though I am not entirely sure. There more than likely would be some gunk that is soluble in the nonpolar that would be worth cleaning out.
Ive been meaning to try making an extract like this for a while myself. I like the effects of kava, they are very unique, almost like a drunken soberness, but the taste of the beverage is horrible in my opinion.
Kava isnt that expensive, best thing to do is try it out and report your results.
--------------------------------------------------*Kash's LSA Extraction* * Kash's Mescaline Extraction*------------------------------------------------------ All things I say are complete and utter ramblings of nonsense. Do not consider taking anything iterated from the depths of my subconsciousness rationally and/or seriously.