Phytoequivalence in the global marketplace for botanical products: chemical and biological characterization of Equisetum arvense extracts from America, Asia, and Europe
Manufacturers of herbal supplements and medicines obtain raw material from worldwide sources. For example, extracts of Equisetum arvense (Horsetail), a perennial herb native to the northern hemisphere, is available from suppliers in America, Asia, and Europe. Horsetail is known for its diuretic and antioxidant activity and is used in dozens of products claimed to promote general wellbeing and the health of hair, nails, skin, and bone. Manufactures often consider herbal extracts from various sources to be interchangeable if they were prepared from the same species using similar extraction solvents and procedures resulting in comparable extraction ratios. An increasing body of evidence indicates, however, that these parameters are not sufficient to ensure that extracts are phytochemically and pharmacologically equivalent. The notion that herbal extracts should be considered equivalent and interchangeable only when they exhibit both matching chemical composition and pharmacological activity is encapsulated in the term of phytoequivalence, which was coined in the last decade in Germany. We conducted the present study in order to characterize the extent of variation in commercially available extracts of E. arvense. We used phytochemical profiling by HPTLC, HPLC-PDA-MS/MS to characterize extracts of E. arvense originating from America (n=7), Asia (n=4), and Europe (n=2). As one measure of pharmacological activity, we determined the free radical scavenging activity of the extracts. In cases where suppliers provided us with the plant material used in the preparation of the commercially available extracts, we performed DNA barcoding and fingerprinting for genomic authentication of the herbs. The experiments revealed qualitative and quantitative differences between the extracts such as in their content of flavonoid glycosides and phenyl carboxylic acids and their radical scavenging activity. Ongoing work is directed at the elucidation of the sources of variation as well as their functional significance with the aim to develop better criteria for the determination of phytoequivalence of extracts from different suppliers.