In a multi-step process for selectively purifying various pharmacologically-relevant components of a source plant such as cannabis, an initial step of the process provides a low-temperature, robust essential oil/terpene capture that also dehydrates and decarboxylates the starting—fresh raw cannabis—by means of a vacuum-assisted microwave distillation process. By doing the terpene capture under vacuum distillation temperature may be kept low. The low distillation temperature maximizes yields of thermally-sensitive components such as terpenes and cannabinoids. The process includes additional steps of: extract cannabinoids from the dehydrated cannabis to produce a crude extract via a supercritical CO2 extraction process; purify crude extract of fats, lipids, plant material; and distill relevant cannabinoids from the purified crude extract via a wiped-film process. Selected terpenes and cannabinoids are then recombined in predetermined proportions to achieve extracts of unusual purity and having targeted therapeutic profiles.