Even when correctly authenticated, it is important to realize that different batches of the same herbal ingredient may differ in quality due to a number of factors. These factors include:
1. Inter or intra-species variation:
The variation in constituents is mostly genetically controlled and may be related to the country of origin.
2. Environmental factors:
The quality of a herbal ingredient can be affected by environmental factor like climate, altitude and other conditions under which it was cultivated.
3. Time of harvesting
For some herbs, the optimum time of harvesting should be specified as it is known that the concentrations of constituents in a plant can vary during the growing cycle or even during the course of a day.
4. Plant part used
Active constituents usually vary between plant parts and it is not uncommon for a herbal ingredient to be adulterated with parts of the plant not normally utilized. In addition, plant material that has been previously subjected to extraction and is therefore ‘exhausted’ is sometimes used as adulterants to increase the weight of a batch of herbal ingredient.
5. Post-harvesting factors
Storage conditions and processing treatments can greatly affect the quality of a herbal ingredient. Inappropriate storage after harvesting can result in microbial contamination. In addition, processes such as drying may result in a loss of thermo-labile active constituents.