Because of their natural diversity it is not possible to describe all herbs and herbal products as a single entity. The herbal raw material is prone to a lot of variation due to several factors, the important ones being the identity of the plants, seasonal variation, the ecotypic, genotypic and chemotypic variations, drying and storage conditions and the presence of xenobiotics. Unlike pure drugs, herbal drugs are complex mixtures of constituents of a single herb or several of them. It is therefore much more difficult to characterize such complex mixtures than a pure compound. Hence standardizing herbal drugs using approaches developed for pure drugs is not going to work. Though the advancements in modern methods of analysis and the development of their application have made it possible to solve many of these problems, development of standards for plant-based drugs is a challenging task and needs innovative and creative approaches different from routine methods. There is an urgent need to ensure quality of the ever-expanding volume of herbals that manage to reach the market.

The WHO stresses the importance of the quantitative and qualitative methods of characterizing samples, quantification of biomarkers and/or chemical markers and the fingerprint profiles. These products should be free of adulteration; free of deliberately added non-authentic plant material which may be biologically active or inactive; other additives such as herbicides, pesticides, heavy metals and solvent residues; and also free of microbial and other biological contaminants. Methods of standardization should take into consideration all aspects that contribute to the quality of herbal drugs.

A number of official monographs for the standardization of botanicals have been developed in countries across the world. Monographs of plant materials of long-established commercial use are being developed similar to pure drugs. Research and evaluation of herbal medicines without a long history of usage or those which have not been previously researched should follow regulations of WHO’s Research Guidelines for Evaluating the Safety and Efficacy of Herbal Medicines.

Other scientific challenges regarding herbal remedies are to establish more completely their dissolution, bioavailability and shelf life.

One of the first requirements in herbal drug development is the need to create a uniform product for controlled, double blind, cross over, placebo-controlled clinical trials.