I would first like to ask that why would u need to encapsulate plant extract rather than pure component in the liposomes. since liposomal encapsulation is done with pure components with rationale to narrow down their adverse effects and increasing targeting benefits associated with targeting ligands. First thing should be to find out the molecular moiety which causes the desired effect and then encapsulating it would be preferable. Because plant extract themselves tend to containing active agent plus theri neutralizing agents generally on systemic scale. Nevertheless if still there comes a rationale for the extract then try to make a stable dispersion of the extract in a solvent system which  has hydrophillic dispersion medium. the next step would be to select and dissolved the liposomal components or ingredients in the systems and then applying pulsatile shots of sonicator using tip sonicator. 30 -45 mins of sonication should give u the desired results.  

 In order to check the synergistic effects of all the bio-active compounds in an extract with enhanced bio-availability. 

Can you please refer to some protocol for the above mentioned method ?

" the next step would be to select and dissolved the liposomal components or ingredients in the systems"

you referring to  which systems ? its unclear. How would sonication be giving the desired results ? As I want to check the amount of extract encapsulated in the liposomes ? by dissolving the liposomal components I will end up the extract in the medium my question is still there how will i be quantifying that ? 

ROTA EVAPORATION IS BEST METHODE AND WE GET MAXIMUM ENTRAPMENT AND DESIRED VESICLES.MOST CELEBRATED METHODE FOR LIPOSOMAL FORMULATIONS.