Medicinal plants are used throughout the world
and the regulations defining their proper use such as
identification of the correct species and verification of the
presence purity and concentration of the required chemical
compounds are widely recognized. Herbal medicines are made from
vegetal drugs the processed products of medicinal species. These
processed materials present a number of challenges in terms of
botanical identification and according to the World Health
Organization (WHO) the use of incorrect species is a threat to
consumer safety. The samples used in this study consisted of the
dried leaves flowers and roots of 257 samples from 8 distinct
species approved by the WHO for the production of medicinal herbs
and sold in Brazilian markets. Identification of the samples in
this study using DNA barcoding (matK rbcL and ITS2 regions)
revealed that the level of substitutions may be as high as 71%.
Using qualitative and quantitative chemical analyses this study
identified situations in which the correct species was being sold
but the chemical compounds were not present. Even more troubling
some samples identified as substitutions using DNA barcoding
contained the chemical compounds from the correct species at the
minimum required concentration. This last situation may lead to the
use of unknown species or species whose safety for human
consumption remains unknown. This study concludes that DNA
barcoding should be used in a complementary manner for species
identification with chemical analyses to detect and quantify the
required chemical compounds thus improving the quality of this
class of medicines.
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