Commercial peppermint (Mentha × piperita L.) teas: Antichlamydial effect and polyphenolic composition Karmen Kapp a , Elina Hakala a , Anne Orav b , Leena Pohjala c , Pia Vuorela c , Tõnu Püssa d , Heikki Vuorela a , Ain Raal e, ⁎ a Division of Pharmaceutical Biology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56 (Viikinkaari 5 E), FI-00014 Helsinki, Finland b Institute of Chemistry of Tallinn University of Technology, Akadeemia tee 15, 12628 Tallinn, Estonia c Pharmaceutical Sciences Laboratory, Department of Biosciences, Åbo Akademi University, BioCity, Artillerigatan 6 A, FI-20520 Turku, Finland d Department of Food Hygiene, Estonian University of Life Sciences, Kreutzwaldi 58A, 51014 Tartu, Estonia e Department of Pharmacy, University of Tartu, Nooruse 1, 50411 Tartu, Estonia abstract article info Article history: Received 16 November 2012 Received in revised form 5 February 2013 Accepted 9 February 2013 Keywords: Mentha × piperita Gram-negative Intracellular bacteria Antibacterial activity Polyphenolic compounds Essential oil The qualitative and quantitative polyphenolic contents in the infusions of the commercial peppermint tea (Mentha × piperita L.) samples (n = 27) from different countries were studied using HPLC–UV-MS/MS anal- ysis. The most abundant polyphenolics in the peppermint infusion were eriocitrin, 12-hydroxyjasmonate sul- fate, luteolin-O-rutinoside and rosmarinic acid. In order to evaluate the content of samples by finding chemosystematic markers, the essential oil composition was studied by GC. The analyses showed that the 24 (89%) peppermint tea samples contained peppermint, whereas three samples may contain Mentha spicata, different from that claimed on the package. The effects of seven peppermint tea extracts against respiratory tract pathogen Chlamydia pneumoniae were investigated in vitro. All seven selected tea extracts were active against C. pneumoniae, the growth inhibition ranging from 20.7% to 69.5% at extract concentration of 250 μg/ml. In most cases, the antichlamydial activity was related to the peppermint teas having also high content of luteolin and apigenin glycosides. This study supports the consumption of peppermint tea to potentially elicit beneficial health effects on acute respiratory tract infections. © 2013 Elsevier Ltd. All rights reserved. 1. Introduction Tea is a popular and inexpensive beverage, highly valued all around the world. It is consumed by a range of age groups at all levels of the so- ciety and about three billion cups of tea are consumed daily worldwide (Hicks, 2009). During the last decades, there has been a resurgence of in- terest in herbal teas both in medicinal and non-medicinal purposes. With concerns about the possible adverse effects of consuming beverages containing caffeine, the health-oriented people are turning to herbal teas as alternatives to coffee, cocoa and common tea (Manteiga, Park, & Ali, 1997; Perumalla & Hettiarachchy, 2012). Peppermint (Mentha × piperita L.) tea is a popular single ingredi- ent herbal tea, known for its refreshing taste and aroma. It is an old medicinal plant species in the Eastern and Western traditions and the list of peppermint uses as a folk remedy or an alternative medical therapy includes irritable bowel syndrome, flatulence, indigestion, nausea, vomiting (Grigoleit & Grigoleit, 2005), cough and bronchitis (Shkurupii, Odintsova, & Kazarinova, 2006). Furthermore, it is well documented that the essential oil or extracts of M. × piperita possess antimicrobial, fungicidal, antiviral, insecticidal, radioprotective, and anti- oxidant activities (McKay & Blumberg, 2006; Peixoto, Furlanetti, Anibal, Duarte, & Höfling, 2009; Rita & Animesh, 2011). Perhaps therefore, pep- permint has been announced as the “medicinal plant of the year” (Saller, 2004). It is well established that the quality and flavor of an herbal tea are principally determined by both volatile compounds, contributing to the property of aroma, and non-volatile compounds, contributing to the taste (Scharbert & Hofmann, 2005). However, it has been reported that peppermint infusion may contain only 21% of the original essential oil of the starting material, while 75% of the original polyphenolic con- tent is extracted (Duband et al., 1992). For this reason, attention should be focused on polar compounds such as polyphenolic compounds that are more stable during boiling and storage (Mimica-Dukic & Bozin, 2008). Despite advances in antibiotic therapy, respiratory infections remain one of the most common diseases and even cause of death worldwide especially among children and elderly. Chlamydia pneumoniae is a gram-negative intracellular bacterium with a unique developmental life-cycle, including an infective metabolically inactive elementary body (EB) and a metabolically active reticulate body (RB). It is established as an important respiratory pathogen (Saikku, 1992) that infects nearly Food Research International 53 (2013) 758–766 ⁎ Corresponding author. Tel.: +372 7375281; fax: +372 7375289. E-mail address: ain.raal@ut.ee (A. Raal). 0963-9969/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodres.2013.02.015 Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres