Natural products have been a major source of drugs for centuries. With more than 25% of the pharmaceuticals in use today from natural products. This can be attributed to several factors, including unmet therapeutic needs that drive drug discovery, the remarkable diversity of both chemical structures and biological activities of naturally occuring secondary metabolities and etc.
Prior to the early-mid 20th century, the use of natural products was limited pricipally to crude plant preparations and was based largely on empirical observation.
The early observations the use of plants to control illness and injury were recorded as the various materia medica of the traditional and folkloric remedies in various cultures. Following an era of purely ‘phytochemical’ investigation came a period in which the biological effects of pure natural products and the important and pivotal role of natural products in understanding pharmacological and cellular processes were recognized. For example; the isolation and structure determination of morphine from Papaver somniferum.
Definition of Natural Product Terms
Pharmacognosy: Study of all aspects of biologically active natural products and/or their derivatives, and encompasses the chemistry of all living organisms
Natural product: Single chemical compound that occurs naturally.
Dereplication: Process of determining whether an observed biological effect of an extract or specimen is due to a known substance
Bioassay-directed fractionation: Process of isolating active constituents from some type of using a decision tree that is directed solely by bioactivity.
Biosynthesis: Process an organism uses to synthesize a chemical constituent.
Semi-synthesis: Synthetic modification of a natural product
Combinatorial biosynthesis: Process of generating novel molecules from natural products by the genetic engineering of biosynthetic pathways in organisms
Approaches to Discovering and Developing Natural Products as Potential New Drugs
One of challenges is how best to determine desirable biological activity. In the beginning, this was largely a trial and error process. Through the years this process gave way to an equally random, but more scientifically validated process known as ‘screening’. It is in this area that much debate regarding how best to discover a potential new drug rages. The goal is to survey as much specimen diversity as is possible. New assays using a specific target enzyme or receptor are rapidly developed and adapted for high throughput screening and these advancements have led to turnover of assays.
Strategies and Approaches for Sourcing, Processing, and Archinig Natural Products for Drug Discovery
The goal of sourcing and sample acquisition is; to obtain the maximum chemodiversity and therapeutically useful biological activity within the minimum number of collected
samples. The goal of sample handling and preparation is; to remove nuisance compounds that may interfere with bioassays in a nonspecific manner, to prepare the samples to be compatible with existing bioassays, and to store both the collected, unprocessed material and the processed samples in a manner that is easily retrievable and maximizes stability.
Some strategies in use today include :
- utilizing ethnobotanical and folklore information on medicinal plant use by specifis cultures,
- exploring the relationdhips of genetic biodiversity and environmental factors to chemodiversity and specific biological activties,
- examining the chemical ecology of plants and animals, focusing on plants, microbes, or animals that exist in unusual habitats,
- investigating whether different plant parts and ages of plants are more likely to produce novel bioactive natural products, and biodiversity prospecting.
The greatest biodiversity occurs in the tropical regions and the greatest ethnobotanical knowledge exist within various cultures that do not use ‘Western medicine,’ both of which often occur in developing countries. There are three sources of natural products; plants, microorganisms and animals.