Mechanochemically assisted extraction involves the mechanical treatment of powder mixtures of plant materials and convenient reagents in special mill-activators to solubilize the biologically active substances. The reactions of the solid hydroxides, carbonates, and hydrocarbonates of alkali metals are the subject of this paper. During mechanochemical treatment, insoluble biologically active substances are transformed into water-soluble or highly reactive mechanocomposites. The types of reagents used depend on the chemical nature of the biologically active substance and the possible chemical reactions between the substance and reagents. Solid-state mechanochemical reactions between active acids and solid bases and between biogenic amines and acids and the formation of soluble complexes of biologically active substances with watersoluble and insoluble polymers were explored in this study. The advantages of using these reactions in mechanochemically assisted extraction are presented in this review.