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Abstract
During recent years, ayurvedic plants have entered the European market as a novel food trend. This confronts food analytics with the task to assess the composition of exotic and often unknown herbal preparations in teas or spices. Using the trend plant 'Tulsi' (Holy Basil, Ocimum tenuiflorum L.) as model, we developed microscopical diagnostics on markers that can be reliably assessed in dried or even fragmented specimens as typically occurring in commercial ayurvedic preparations, where DNA extraction is difficult. First, a reference for 'Tulsi' was defined based on the plastidic internal transcribed spacer (ITS) as marker. Second, this reference was morphologically delineated from other Ocimum accessions potentially used as surrogates for 'Tulsi' (such as O. basilicum L.) leading to a microscopical assay based on the density of glandular scales and glandular hairs, the epidermis with trichomes and the cells of the palisade parenchyma. Third, this assay was statistically validated for its ability to discriminate surrogate species from true O. tenuiflorum. First applications of this assay on commercial 'Tulsi' products demonstrated a high frequency of surrogate additions. [PUBLICATION ABSTRACT]