Essential oil chemical diversity of Tunisian Mentha spp. collection

Mints are perennial herbs that are cultivated for medicinal and aromatic purposes. They are highly polymorphic and their taxonomy is difficult. Sixty mint accessions, representing seven Mentha species (M. aquatica L., M. longifolia L, M. piperita L., M. pulegiwn., M. rotundifolia L., M. spicata L. and M. spicata var. crispa 'moroccad), were collected at full flowering from 51 Tunisian localities. Essential oil yields were found to vary from 0.45 to 2.5%, (w/w). Analyses of these oils by GC/FID and GC/MS and their subsequent classification by statistical analysis resulted in six clusters with significant variations in their terpenoid compositions: i) pulegone/isomenthone/menthone; ii) isomenthone/pulegone; iii) menthone/pulegone; iv) piperitenone oxide; v) linalool/linalyl acetate/1,8 cineol/myrcene; and vi) carvone/limonene/1.8 cineol. M. pulegium accessions grouped two chemotypes: one rich in pulegone and the second rich in isomenthone. M. longifolia grouped one chemotype rich in pulegone and a second rich in menthone. M. spicata grouped one chemotypes characterized by a moderate to high carvone content and the second pulegone-rich. M. rotoundifolia accessions were piperitone oxide-rich. M. aquatica and M. piperita have linalool and linalyl acetate as major compounds. These results clearly indicate that there were a large biochemical diversity among the investigated Tunisian Mentha spp. accessions. Genetic and ecological diversities may explain this chemical diversity.