Phenolic compounds and antimicrobial properties of mint and thyme

Mint ( Mentha spp.) and thyme ( Thymus spp.) are two of the foremost aromatic herbs used in food and beverage products for their flavor, aromatic and medicinal qualities. These species belong to the tribe Mentheae, part of the mint family (Lamiaceae), which comprises many genera of well-known culinary and medicinal herbs. This review examines the phenolics in mint and thyme as natural health-promoting phytochemicals and potential antimicrobial drugs. Compounds examined here include carvacrol, thymol, p -cymene, carvone, menthol, menthone, pulegone, limonene, 1,8-cineole and cinnamaldehyde. Literature searches were performed using nine databases to obtain peer-reviewed studies on the phytochemical complements of mint and thyme and the properties of individual bioactive compounds. The medicinal benefits of mint and thyme include their digestive, antiseptic, antispasmodic, antirheumatic, expectorant, antiallergic, antitussive, antioxidant and antimicrobial activities. Essential oils of these aromatic plants are utilized for a wide variety of applications, such as to impart fragrance and flavoring to cosmetics and spice mixtures, and as components of repellents and pesticides. Phenolic compounds, comprising phenols and polyphenols, are the most abundant secondary metabolites in the extracts and essential oils of mint and thyme. It was concluded from the literature that only a limited number of the phytochemical activities of mint and thyme have been explored, and that further interdisciplinary research efforts into the biological and molecular mechanisms of these compounds is likely to yield important findings in herbal medicine. • Mint and thyme leaves, young stems and inflorescences are harvested for their essential oils. • The chief constituents of mint oil include menthone, menthyl acetate, menthol and terpenes. • Menthol is isolated industrially from mint oil via several processes and made synthetically. • Thyme is one of the most important natural sources of thymol and carvacrol. • The antimicrobial activities of mint and thyme are due to a wide range of diverse phenolics.