Natural variability chemotypes

A serious problem in the early Western medicinal use of C. sativa, mainly as a tincture, was its highly variable activity and inconsistent results. Medicinal preparations have to handle several particularities due to the structure of the active ingredients of C. sativa. The identity of the main active constituent of C. sativa, A9-tetrahydrocannabinol (INN dronabinol) remained unknown until 1964 [128] standardized C. sativa preparations were not available. The plant itself is found in several different chemotypes, which added to the unpredictable nature of early medicinal preparations. 

Fennel oleoresin is prepared by solvent extraction of whole seeds and normally contains a volatile oil of 50% or a guaranteed content in the range of 52-58%. Only small quantities are produced for specific uses as it is not a substitute for fennel oil. Chemical analysis by Barazani et al. (2002) of the volatile fraction of oleoresins from fruits of seven natural populations of F. vulgare var. vulgare (bitter fennel) from the wild and after cultivation indicated the presence of two groups of populations. Chemotypic differentiation (relative contents of estragole and trans-anethole) or phenotypic plasticity increases within-species chemical variability, but the specific ecological roles of these essential oils remain to be uncovered. 

Variability of chemotypes continues also within the marjoramy O. majorana. Novak et al. (2002) detected in cultivated marjoram accessions additionally to c -sabinene hydrate the occurrence of polymorphism of cw-sabinene hydrate acetate. Since this chemotype did not in uence the sensorial impression much, this chemotype was not eliminated in breeding, while an ojf-flavor chemotype would have been certainly eliminated in its cultivation history. In natural populations of O. majorana from Cyprus besides the classical CM-sabinene hydrate type, a chemotype with a-terpineol as main compound was also detected (Novak et al., 2008). The two extreme ojf-flavor chemotypes in 0. majorana, carvacrol and a-terpineol chemotypes, are not to be found anywhere in cultivated marjoram, demonstrating one of the advantages of cultivation in delivering homogeneous qualities. 

The common and large variability in the composition of natural EOs poses dif culties for the evaluation and the safe and effective use of aromatic medicinal plants. Genetic variations lead to the occurrence of chemotypes, as in the case of Lippia alba (P. Mill.) N.E. Br. ex Britt. Wilson (Verbenaceae). Analyses revealed three monoterpenic chemotypes characterized by the prevalence of myrcene (1 and citral (1 in the chemotype I, limonene (14) and citral (16) in the chemotype II, and limonene (14) and carvone (17) in the chemotype III (Matos 1996). This species is known in Brazil as cidreira the aromatic tea from its leaves is traditionally used as a tranquilizer, being one of the most widely known homemade remedies. Pharmacological assays showed anxiolytic (Vale et al. 1999) and anticonvulsant (Viana et al. 2000) effects of EO samples from all three chemotypes. Anticonvulsive and sedative effects in mice were also demonstrated for the three isolated principal constituents ofL. alba oils limonene (14), myrcene (15), and citral (16) (Vale et al. 2002). 

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