Herbal medicine is a valuable clinical tool rich in both science and tradition. Herb quality is critical to having confidence in a formula, but it has always been challenging when it comes to determining the best methods to identify and quantify specific compounds in a plant or extract.
Laboratories offer a variety of constituent testing method options. One sophisticated and expensive test is HPLC, also known as High Performance Liquid Chromatography. You may remember seeing this test in organic chemistry classes; HPLC testing shows individual spikes on a chromatogram which identify specific chemical compounds or “biomarkers”. For many of the medicinal extracts, HPLC is the ideal method for accurately identifying and quantifying particular biomarkers in an extract or plant.
When an herbal supplement label states “minimal constituent biomarker per dose” for a particular herb, it is an indication that HPLC testing has been conducted. The amount indicated is the average amount the manufacturer can guarantee of that particular biomarker in each dose. This helps the physician to calculate the dosage required to achieve optimal therapeutic efficacy.
A more common and less expensive testing method is UV or ultraviolet spectrometry, which is used to identify a class of herbal markers in an extract. Because UV testing is cost effective, it is a commonplace test used in the supplement industry. The downside of UV testing is that it is not as accurate and specific in identifying exact compounds, and is prone to counting all constituents within a bandwith. One example is in testing the herb milk thistle; UV spectrometry counts all flavonoids in a sample and is unable to isolate silymarin specifically. This means that the percentage of silymarin in an extract, when identified by UV, will be stated on the label as artificially higher than the actual value because it includes all flavonoids. (or they don’t test every batch)
Because HPLC is so specific, it will show a lower concentration of silymarin in a sample as compared to a UV test, which includes other flavonoids. Unfortunately, labels are not required to specify the testing methods used, making it confusing to the average herb user. Almost all silymarin is tested by UV and this is where the standard 80% silymarin was derived.
Restorative Formulations committed to maintaining the highest possible standards, and uses HPLC testing on applicable herbs to identify average minimum constituent biomarkers per dose. Chemical markers can change over the course of plant life, based on seasons, harvesting time, and processing conditions. Independent testing is done on every batch, although industry standards allow the common practice of skipping batches. Restorative Formulations calculates the average of the HPLC test results, and lists 20% list to guarantee the minimal levels anticipated over the life of the product.
S. Rajasekar and R. Elango.

Journal of Experimental Sciences 2011, 2(5): 39-41
Sameh AbouZid (2012). Silymarin, Natural Flavonolignans from Milk Thistle, Phytochemicals – A Global Perspective of Their Role in Nutrition and Health, Dr Venketeshwer Rao (Ed.), ISBN: 978-953-51-0296-0
