The fact that, of the approximately 600,000 plant species existing on the earth, only some 5 % have been specifically investigated chemically or pharmacologi cally, is a challenge to chemists spezializing in na tural substances and to pharmacologists. In view of the limited number of research capacities and the ever diminishing financial means, this challenge can only be met if, together with an improvement and refinement of methods of analysis, medicinal plant research is carried out on a broader interdisciplinary basis, with comparable, scientifically recognized screening methods, and if it is better coordinated, with greater use of modern documentation means. It is thus necessary in the future to concentrate specifically on projects leading to the development of new medicinal prepara tions. The plenary lectures hold in the present symposium of the 1st International Congress for Research on Medi cinal Plants reflect these efforts and tendencies. At the same time they provide a survey of some of the fields of medicinal plant research which are at present most actual and most intensively researched. They range from plant screening, isolation and structure eluci dation of new principles, to the therapeutical opti mization of a natural product. The lectures given at this congress show clearly the necessity, in addition to national phytochemical so cieties, for a central international organisation, in which all active medicinal plant researchers in the world are included. Their aim should be to provide the impulse for more optimal, rational research, aimed at the solution of specific projects.

Inhalt
Problems and Prospects of Discovering New Drugs from Higher Plants by Pharmacological Screening.- A. Introduction.- B. Value of Drugs Obtained from Higher Plants.- C. Apathy in Plant-Derived Drug Development.- D. Current Level of Worldwide Research on Plant-Derived Drugs.- E. Pharmacological Screening Programs for Plant Extracts.- F. Problems in the Pharmacological Screening of Extracts from Higher Plants.- G. Prospects for the Future.- References.- Pharmacological Approaches to Natural Product Screening and Evaluation.- A. Ideal Requirements for a Primary Screen.- B. Past Approaches to Primary Pharmacological Screening.- C. Multidimensional Primary Screening.- D. Multidimensional Secondary Screening of Extracts and Pure Compounds.- E. Tertiary Evaluation.- F. Addendum-Sample Print-Out of Computerized Hippocratic Evaluation.- References.- Recent Experimental and Clinical Data Concerning Antitumor and Cytotoxic Agents from Plants.- A. Introduction.- B. Terpenoids.- C. Miscellaneous Compounds.- D. Alkaloids.- E. Summary.- References.- Recent Advances in the Field of Antibiotics.- A. Introduction.- B. Acetate/Propionate-Derived Metabolites.- C. Isoprenoid Metabolites.- D. Amino Acid-Derived Metabolites.- E. Conclusion.- References.- Progress in the Chemistry of Alkaloids with Pharmacological or Biological Activity.- References.- Plant Mono-, Di- and Sesquiterpenoids with Pharmacological or Therapeutical Activity.- A. Introduction.- B. Classification.- C. General Biological Properties.- D. Monoterpenes.- E. Sesquiterpenes and Diterpenes.- F. Conclusion.- References.- Saponins with Biological and Pharmacological Activity.- A. Introduction.- B. Saponins of Licorice.- C. The Saponins of Bupleuri Radix and Platycodi Radix.- D. Saponins of Polygalae Radix and Senegae Radix.- E.Saponins of Akebiae Vitis.- F. Aescin, the Saponins of the Seeds of Aesculus hippocastanum.- G. Saponins of Ginseng.- H. Saponins of Zizyphus Spinosi Semen.- I. Concluding Remarks.- References.- Dimeric Natural Compounds with Pharmacological Activity.- A. Definitions and Classification.- B. The Formation of Dimeric Compounds.- C. Pharmacological and Physiological Activity.- References.- Chemical and Biological Investigations on Indian Medicinal Plants.- A. Introduction.- B. Alkaloids.- C. Oxygen Heterocycles.- D. Terpenoids.- E. Glycosides.- F. Miscellaneous.- References.- Chemistry of Neolignans with Potential Biological Activity.- A. Introduction.- B. Benzofuranoid Neolignans.- C. Benzodioxane and Other Neolignans.- D. Bicyclo [3, 2, 1] octanoid Neolignans.- E. Biogenesis of Neolignans.- F. Conclusion.- References.- Natural Substances with Effects on the Liver.- References.- The Modification of Natural Substances in the Modern Drug Synthesis.- A. Introduction.- B. Main Part.- References.