Problems of Reproducibility and Efficacy of Bioassays Using Crude Extracts, with reference to Aloe vera

semi-synthetic analogues of phytochemicals.It has been estimated that approximately 25% of all prescription drugs currently in use are of plant origin. [2,3] Furthermore, approximately 75% of new anticancer drugs marketed between 1981 and 2006 were derived from plant compounds. [3] Traditionally, plant based medicines have been used as crude formulations such as infusions, tinctures and extracts, essential oils, powders, poultices and other herbal preparations.The current trend is to isolate and characterise the individual phytochemical components with the aim of producing an analogue of increased bioactivity/bioavailability.Such studies have given rise to many useful drugs such as quinine (from Cinchona spp.) and digoxin (from Digitalis spp.) as well as the anticancer drugs vincristine and vinblastine (from Vinca rosea).However, the bioactivities seen for crude extracts are often much enhanced, or even totally different to those seen for the individual components. [4,5] Crude plant extracts may contain hundreds, or even thousands of different chemical constituents that interact in complex ways.Often it is not known how an extract works, even when its therapeutic benefit is well established.The study of crude extracts is itself fraught with difficulties.Plants grown under varied conditions will often produce different phytochemical profiles, or at least different quantities of the individual components. [6,7]Similarly, different cultivars within a Problems of Reproducibility and Efficacy of Bioassays UsingCrude Extracts, with reference to Aloe vera