extracting organic alkaloids?

The alkaloids are basic, and will be nonpolar in basic solutions.
So they will probably go into the xylene layer to start with, and you may want to add a little aqueous base to make sure they go into the xylene.  So you will have plant fats, alkaloids, and other crap in the xylene.

Then shake the xylene with dilute aqueous acid, which should protonate the basic alkaloids and make them water-soluble.  They will go into the water solution, leaving the fats behind.

Separate out the water solution, and make it basic again (add NaOH etc) to convert the alkaloids to their nonpolar free bases.   Wash with xylene, hexane, or some other nonpolar solvent (I like dichloromethane) to extract the alkaloid free base out of the water solution.

Then it's time for chromatography to separate the alkaloids you want from those you don't want.