Mexican tarragon (Tagetes lucida) is an herbaceous, endemic plant in Mexico and Central America, which is used widely in traditional medicines. It is cultured for its pungent aromatic foliage, used as a flavouring, and flower heads, which are used in herbal treatments.

The Tagetes family of plants contain biologically active secondary metabolites including flavonoids, stilbenes, phenyl-propanoids and terpenes. These compounds exhibit anti-inflammatory, antioxidant, antiviral, platelet antiaggregant and nematicidal activities. Coumarin isomers are widely distributed in the Tagetes genus, with their formation involving a direct stereochemically controlled coupling glycosylation and light-mediated isomerization. These processes depend on the regiochemistry and stereochemistry of the initial linkage.

Coumarin, umbeliferone, scopoletin and scoparone are important parent coumarins, which exhibit potent biological activities. They are also chemical mediators in insect-plant relationships. However, there is relatively little information about the phytochemical composition and antimicrobial properties of Mexican tarragon and its potential use as a nutraceutical.

A study by Cespedes et al.¹ investigated the antibacterial and antifungal activities of extracts from Mexican tarragon and identified the coumarins and flavonoids present in the plant. Seven coumarins and three flavonoids were isolated from the extracts of aerial parts. Coumarins were the most effective compounds against Gram-negative bacteria, in particular against Vibrio cholerae, a key bacterium in contaminated water. The dimethoxy coumarins (umbeliferone and scoparone) showed a strong activity against fungal strains. This plant could therefore have an important role in food preservation and food preparation.
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¹ Cespedes, CL; Avila, JG; Martinez, A; Serrato, B; Calderon-Mugica, JC; Salgado-Garciglia, R (2006). Antifungal and antibacterial activities of Mexican tarragon (Tagetes lucida). Journal of Agricultural and Food Chemistry 54 (10) 3521-3527.

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