DNA barcoding methods originally developed for the identification of plant specimens have been applied to the authentication of herbal drug materials for industrial quality assurance. These methods are intended to be complementary to current morphological and chemical methods of identification. The adoption of these methods by industry will be accelerated by the introduction of DNA-based identification techniques into regulatory standards and monographs. The introduction of DNA methods into the British Pharmacopoeia is described, along with a reference standard for use as a positive control for DNA extraction and polymerase chain reaction (PCR). A general troubleshooting chart is provided to guide the user through the problems that may be encountered during this process. Nevertheless, the nature of the plant materials and the demands of industrial quality control procedures mean that conventional DNA barcoding is not the method of choice for industrial quality control. The design of DNA barcode-targeted quantitative PCR and high resolution melt curve tests is one strategy for developing rapid, robust, and reliable protocols for high-throughput screening of raw materials. The development of authentication tests for wild-harvested L. is used as a case study to exemplify these relatively simple tests. By way of contrast, the application of next-generation sequencing to create a complete profile of all the biological entities in a mixed herbal drug is described and its potential for industrial quality assurance discussed.

Using the Indian medicinal plant Tulsi (Holy Basil) as a case study, we have tested to what extent the discrepancy between vernacular and scientific nomenclature can be resolved, whether the presumed chemical diversity underlying the medicinal use of Tulsi has a genetic component, and whether it is possible to detect this genetic component using genetic barcoding markers. Based on four plastidic markers, we can define several haplotypes within Ocimum that are consistent across these markers. Haplotype II is congruent with O. tenuiflorum, while haplotype I extends over several members of the genus and cannot be resolved into genetically separate subclades. The vernacular subdivision of Tulsi into three types (Rama, Krishna, Vana) can only be partially linked with genetic differences–whereby Rama and Krishna Tulsi can be assigned to O. tenuiflorum, while Vana Tulsi belongs to haplotype I. This genetic difference is mirrored by differences in the profiles of secondary compounds. While developmental state and light quality modulate the amplitude to which the chemical profile is expressed, the profile itself seems to be linked with genetic differences. We finally develop an authentication assay that makes use of a characteristic single nucleotide polymorphism in one of the barcoding markers, establishing a differential restriction pattern that can be used to discriminate Vana Tulsi.

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