Methods for extracting and concentrating cannabinoids using ultrasound-enhanced solvent extraction. Freshly harvested cannabis plant materials, which may be selectively chosen plant parts or the entire plant itself, are shredded to a particular particle size. The plant material is then mixed with a solvent to form a slurry, and thereafter subjected to ultrasound to release intracellular contents into the solvent. Filtering steps are then applied to remove biomass, waxes and chlorophyll. Water removal and solvent recovery steps are further applied to ultimately derive an extract having high concentrations of target cannabinoids, and in particular cannabidiol (CBD). The methods may be deployed on-site in batch or continuous flow processes, and may further be utilized to derive other types of materials from plants, such as essential oils.