If possible you may use liquid nitrogen to make the extract solid and then apply vacum to remove alcool. A cold trap with a jacket of solid CO2 dissolved in alcool would avoid oil pump distillation. I can't exclude you could apply directly centrifugal force to avoid boiling, like in Rotavapor or in vacuum centrifuges even if this would not be a lyophilization. You may also remove alcool by bubbling nitrogen in tubes with syringe needles kept at moderate pressure and after freezing the residue, you can go on with freeze drying. The activity you look for, should be checked during processing taking out small portion for bioassay.