The present invention provides plants and plant tissues of spearmint (Mentha spicata) with enhanced rosmarinic acid levels, and extracts derived there from. Methods and compositions for production and use of rosmarinic acid from spearmint as a nutraceutical are also provided. In particular, an edible beverage derived from plant tissues of spearmint that comprise more than 77.5 mg/g rosmarinic acid on a dry weight basis, is provided, as well as methods for making such a beverage and for using it to treat an inflammatory or infectious disease.