Up to mid-19th century, the beginning of the era of natural products, plant-derived drugs remained structurally ill-defined. Plant active constituent isolations from crude drugs were successful when the yield was sufficient and the compounds were more amenable to the then available methods of isolations. However such isolations were not possible for most biologically active crude drugs with unstable and/or poor-yield constituents. Also compound characterization required considerable quantities of the isolated constituents. The advent of modern instrumentation and newer techniques in separation science, such as chromatography, made active constituent isolation and identification much simpler as it became possible to complete compound characterizations on tiny quantities of the isolated material. What followed was considerable progress in the isolation of pharmaceutically important natural products. Plant-derived molecules also served as chemical models or templates for the total synthesis of newer drugs.

Successful introduction of plant-derived drugs including morphine, codeine, papaverine, quinine, atropine, hyoscine, reserpine, digoxin, caffeine, emetine, ergotamine, senna glycosides, vincristine, vinblastine, psoralen, pilocarpine and tannic acid marked the beginning of the era of pure drug molecules, which went on to become the stronghold of modern western medicine. Plants continue to be important sources of drugs as evidenced by the introduction of newer drugs, such as paclitaxel, artemisinin, camptothecin, forskolin, sanguinarine etc. The technology involved in the isolation of commercially important phytopharmaceuticals in many cases is patented information. Availability of analytical techniques and sophisticated instrumentation in the last few decades has made it possible to devise commercially feasible techniques for the extraction of several phytomolecules.