I'll answer here so other people get the benefit of the answer :-)
There are two things I would try. One is partitioning the extract between dichloromethane (DCM) and acidic water (I like to use acetic or formic acid, some like to use HCl). Take the aqueous layer and make it basic (I like to use ammonia), and partition again with DCM.. Take the DCM, evaporate, and purify on a column The extract is often ready for prep HPLC. This extraction is inexpensive.
The other method is to use an strong cation exchange (SCX) column. The column can resolve different types of alkaloids making subsequent purification easier. See: http://www.isco.com/WebProductFiles/Applications/101/Application_Notes/AN40_Purification_of_Alkaloids_with_RediSep_Rf_SCX_Columns.pdf