Marco Cosentino et al /J. Pharm. Sci. & Res. Vol.1(3), 2009, 33-43. 33 Antioxidant properties and in vitro immunomodulatory effects of peppermint (Mentha x piperita l.) Essential oils in human leukocytes Marco Cosentino 1 , Raffaella Bombelli 1 , Ario Conti 2 , Maria Laura Colombo 3 , Andrea Azzetti 4 , Antonello Bergamaschi 5 , Franca Marino 1 , Sergio Lecchini 1 1 Department of Clinical Medicine, Section of Experimental and Clinical Pharmacology, University of Insubria, Varese; 2 Alpine Foundation for Life Sciences, Alpine Institute of Chemistry and Toxicology, Blenio (Olivone), Canton Ticino, Switzerland; 3 Department of Drug and Science Technology, School of Pharmacy, University of Torino; 4 Fondazione Fojanini di Studi Superiori, Sondrio; 5 Associazione “Erba Bona”, Comunità Montana Antigorio-Val Formazza, Crodo (VCO), Italy ________________________________________________________________________________________________ Abstract ISSN:0975-1459 Peppermint (Mentha x piperita L.) is popular in folk medicine. Its immune effects however received so far limited attention. In the present study, peppermint oils from two cultivars (RAC 541 and Laimburg) grown in Northern Italy (Valtellina and Val Formazza) were investigated for their effects on human polymorphonuclear leukocytes (PMNs) and peripheral blood mononuclear cells (PBMCs), for their antioxidant activity and for chemical composition. RAC 541 oils were antioxidant at ≥1 g/ml and Laimburg oils at ≥0,01 g/ml. All the oils were cytotoxic for PMNs and PBMCs only at ≥0,1 g/ml. In the 0,01-0,0001 g/ml range, none of the oils affected spontaneous oxidative burst of PMNs, however RAC 541 oils increased stimulated burst. Oils had no effect per se on PBMC proliferation or production of interferon (IFN)- or interleukin (IL)-4. RAC 541 (but not Laimburg) oils however increased PHA-induced proliferation of PBMCs, and RAC 541 oil from Val Formazza (but not Valtellina) and Laimburg oils reduced IL-4 production. Essential oils from Mentha x piperita L. may thus affect the functional responses of human PMNs and PBMCs in a heterogeneous and cultivar-specific fashion. Key W ords: Mentha x piperita L.; essential oil; antioxidant activity; DPPH; TBARS; peripheral blood mononuclear cells; proliferation; interferon-; interleukin-4; polymorphonuclear leukocytes; reactive oxygen species. ________________________________________________________________________________________________ Introduction Peppermint (Mentha x piperita L.), a perennial herb belonging to the Lamiaceae family, is a sterile natural hybrid derived from a cross between Mentha aquatica L. x Mentha spicata L. species. It is native in Europe and it has become both cultivated and naturalised in many European countries and in North America. Its purported benefits and uses as a folk remedy or in complementary and alternative medical therapy regard mainly digestive disorders, however a wide range of pharmacological properties is reported in the scientific literature, including antioxidant capacity, antitumor, antiallergenic, antimicrobial activities, hepatic and renal actions, chemopreventive potential, and nervous system actions (reviewed in 1 and 2). Peppermint is mentioned in Chinese traditional medicine, and dried peppermint leaves were found in Egyptian pyramids, _____________________________________ Phone (direct) +39 0332 217410/397410 Phone (exchange) +39 0332 217401/397401 Fax +39 0332 217409/397409 E-mail marco.cosentino@uninsubria.it suggesting that the use of peppermint may date back to at least 1000 BC [3]. Preparations of peppermint include leafs, leaf extracts and water, however the plant is cultivated mainly for its essential oil, which is obtained by distillation from freshly grounded leaves. Peppermint oil is composed primarily of menthol and menthone together with several other minor constituents, including pulegone, menthofuran and limonene [4], and its chemical composition may vary with plant maturity, geographical region and processing conditions [2]. Heterogeneous reports suggest that peppermint oil and some of its constituents may have immunomodulating properties [5- 16], and peppermint has been included in some mixed formulations patented as effective in conditions such as arthritis and rheumatism [17]. Available evidence is however far from being clear and conclusive and the present study was therefore devised to investigate the effects of various peppermint oils on some functional properties of human peripheral blood mononuclear cells (PBMCs) Journal of Pharmaceutical Sciences and Research www.jpsr.pharmainfo.in