Editorial [Hot topic: Plant Natural Products in Drug Discovery (Guest Editor: Ping Li)]

Plants are the fundamental basis of sophisticated traditional medicines for thousands of years, and continue to be used as valuable medicinal materials in countries where conventional medicine is an important part of the national health care system. During the last decade, medicinal plants, with the characteristics of multiple constituents, multiple actions, and multiple targets, have expanded globally and gained considerable popularity. Meanwhile, natural products from plants provide an unparalleled source of chemical diversity for discovery of important and interesting biologically active molecules. Over 50% of the drugs introduced to the market during the last 20 years are derived directly or indirectly from plant natural products. Undoubtedly, plants will continue to play a major role as lead compounds in the discovery of drug and drug targets. Plants belong to complex multi-component system, and multidisciplinary approaches are thus required to develop validated research methodologies and to increase the productivity in drug discovery and development. It will be the aim of this special issue on Plant Natural Products in Drug Discovery to illustrate the recent advances and to highlight new trends in chemical compositions, sample preparation, analytical techniques, pharmacokinetics, and drug lead discovery based on plant extracts or plant natural products. It is hoped that the scientists involved in natural products and related research fields will find the selection of these reviews, ranging from traditional medicinal chemistry methodologies to new frontiers in plants research and drug discovery, beneficial and informative. Sample preparation is essential for isolating desired components from complex plant matrices and greatly influences the reliability and accuracy of analysis of plant-derived medicines. The first review by H. Kataoka, from School of Pharmacy, Shujitsu University, summarizes current trends in sample preparation techniques for the analysis of plant-derived medicines, focusing primarily on newly developed techniques, such as supercritical-fluid extraction, solid-phase microextraction, and liquid-phase microextraction. Structural elucidation is one of the most challenging tasks for access to plant natural products. The second review, written by X.C. Li et al., from National Center for Natural Products, the University of Mississippi, illustrates the applicability of the time dependent density functional theory calculation of electronic circular dichroism spectra in determining the absolute configuration of structurally diverse natural products and complex chiral molecules. For the purpose of lead discovery, or for the scientific validation of a medicinal plant, active principals in complex matrices need to be analyzed. Analysis of constituents in medicinal plants has been one of the hottes topics for the past 20 years. Gas chromatography, liquid chromatography and electromigration methods are the three most widely used techniques for analysis of plants. The article by L. Mondelloa et al., from Dipartimento Farmaco-chimico, Universita di Messina, reviews modern gas chromatography and hyphenated techniques for analysis of plant extracts including gas chromatography-mass spectrometry, multidimensional gas chromatography, etc. The review by J.L. Wolfendera et al., from School of Pharmaceutical Sciences, University of Geneva, focuses on advances in liquid chromatography hyphenated techniques and direct MS or NMR analysis for profiling crude extracts and for the rapid identification of natural products. The paper by M. Ganzera and I. Nischang, from University of Innsbruck and Johannes-Kepler-University introduces the use of capillary electrochromatography for natural product analysis, including the theoretical background and recent applications. As one typical example, the review by L.W. Qi et al., from Key Laboratory of Modern Chinese Medicines, China Pharmaceutical University, Ministry of Education, is dedicated to Radix Astragali (Astragalus) covering latest advancements and trends in chemistry, analysis, pharmacology and pharmacokinetics. Pharmacokinetic studies are an integral part of modern drug development, and an increasing attention has been paid to pharmacokinetics of plant medicines. The paper by S.F. Zhou et al., from School of Health Sciences, RMIT University, highlights the pharmacokinetic properties and disposition pathways of commonly used plant natural products and the possible clinical and toxicological implications. The review by C.G. Lim and M.A.G. Koffas, from Department of Chemical and Biological Engineering, University at Buffalo, discusses the bioavailability of the major classes of stilbenes and flavonoids, with an emphasis on their absorption, distribution, metabolism and excretion properties...