In our research six different mint species (peppermint, spearmint (five different chemotypes), Horse mint, mojito mint, apple mint (two different chemotypes), bergamot mint) have been evaluated by referring to their chemical (essential oil (EO) content and composition) and in vitro biological (antibacterial, antioxidant effect) characteristics. The EO amount of the analyzed mint populations varied between 1.99 and 3.61 mL/100 g d.w. Altogether, 98 volatile compounds have been detected in the oils. Antibacterial effects (inhibition zones, MIC, IC₅₀ and MBC) were evaluated against Escherichia coli, Salmonella enterica, Bacillus cereus and Staphylococcus aureus. The best antibacterial effect was given by a carvacrol–thymol chemotype spearmint population (inhibition zone: 18.00–20.00 mm, MIC: 0.06 v/v%, IC₅₀: 0.01–0.03 v/v%, MBC: 0.06, >2.00 v/v%). The least effective oil in the case of Gram-negative bacteria was bergamot mint (inhibition zone: 7.67–8.67 mm, MIC: 2.00, >2.00 v/v%, IC₅₀: 0.11–0.25 v/v%, MBC: 2.00, >2.00 v/v%), while in the case of Gram-positive bacteria, oils containing dihydrocarvone as the main compound possessed the weakest antibacterial effect (inhibition zone: 9.00–10.00 mm, MIC: 1.00–2.00 v/v%, IC₅₀: 0.22–0.37 v/v%, MBC: >2.00 v/v%). Interestingly, none of the oils could kill B. cereus in the applied concentrations.

Chemistry, in vitro antioxidant, and antimicrobial effects of Mentha × villosa and its parental species, Mentha spicata and Mentha suaveolens, are discussed. This is the first review of the terpene and phenolic composition of M. × villosa . The volatile chemistry of M. × villosa is evaluated in the mirror of the parental species, discussed based on structural-biogenetical groups of their terpenoids. In spearmint, there is a wide diversity, involving multiple groups of monoterpenes (such as linalool or cymyl compounds). The main volatile components in M. suaveolens are usually rotundifolone or carvone, and these compounds also determine the chemotype in M. × villosa . However, contrary to the parental taxa, M. × villosa chemotypes seem connected to geographical origin. The polyphenol profile of the three taxa is also surveyed, in the framework of shikimate metabolism of genus Mentha . This means especially the high amounts of rosmarinic acid accompanied by flavanones and a variety of flavones. Even flavonols are major components, although they are considered atypical in Mentha . The preparation and extraction methods are also presented for better comparison between compositional data and a survey of methods for the extraction of polyphenols. Regarding bioactivity, much less experimental work has been done on M. × villosa than on the parental taxa. M. × villosa can be a prospective medicinal plant not only used for flavoring. It can be a substitution for carvone-type spearmint. However, much more work is necessary to optimize its cultivation, focusing on different types of components and defining its biological activity properly.