546 R. M. SAMARTH ET AL. Copyright © 2004 John Wiley & Sons, Ltd. Phytother. Res. 18, 546–550 (2004) Copyright © 2004 John Wiley & Sons, Ltd. Received 9 January 2002 Accepted 9 February 2004 PHYTOTHERAPY RESEARCH Phytother. Res. 18, 546–550 (2004) Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ptr.1483 Protection of Swiss Albino Mice against Whole-body Gamma Irradiation by Mentha piperita (Linn.) R. M. Samarth, P. K. Goyal and Ashok Kumar* Radiation and Cancer Biology Laboratory, University of Rajasthan, Jaipur – 302004, India The radioprotective effects of Mentha oil (Mentha piperita Linn.) against radiation induced haematological alterations in peripheral blood and the survival of Swiss albino mice were studied. Mentha oil 40 μL/animal/ day for 3 consecutive days when fed orally prior to whole-body gamma irradiation (8 Gy) showed protection of the animals in terms of the survival percentage and haematological parameters in mice. Fifty per cent of the animals died within 20 days and 100% mortality was observed up to 30 days post-irradiation in the control irradiated group. Whereas only 17% of the mice died within 30 days in the experimental group (Mentha oil pretreated irradiated). The total RBC count decreased maximally at 24 h (3.45 ± 0.20 × 10 12 /L, p < 0.001), similar observations were obtained for the WBC count, haemoglobin content and haematocrit percentage in the irradiated control animals. However, in irradiated animals pretreated with Mentha oil, although the initial values of haematological components were lower they later showed a remarkable recovery reaching normal at 30 days post-irradiation compared with the irradiated control animals. In general, the recovery of the blood cell number in irradiated animals depends on the survival of stem cells and their derivatives. The results from the present study suggest that the oil of Mentha piperita (Linn.) has a radioprotective role in stimulating/ protecting the haematopoietic system. Hence, enhanced survival and an increase in the haematological con- stituents of peripheral blood of mice against lethal gamma radiation was observed. Copyright © 2004 John Wiley & Sons, Ltd. Keywords: gamma radiation; haematological constituents; Mentha piperita (Linn.); radioprotection; Swiss albino mice; survival percentage. * Correspondence to: Dr A. Kumar, Radiation and Cancer Biology Labora- tory, University of Rajasthan, Jaipur 302004, India. E-mail: mamsjpr@hotmail.com Contract/grant Sponsor: CSIR. of India, 1962). Mentha extract has been shown to have antioxidant and antiperoxidant properties due to the presence of eugenol, caffeic acid, rosmarinic acid and α-tocopherol (Rastogi and Mehrotra, 1991; Krishnaswamy and Raghuramulu, 1998; Al-Sereiti et al., 1999). The aqueous extract has also been screened for antibacterial activity against Pseudomonas solanacearum (Lirio et al., 1998). Recently, a radiomodulatory influ- ence of Mentha oil on the serum phosphatases activity of mice has been reported (Samarth et al., 2001). The present study reports the radioprotective effect of Mentha oil against radiation in terms of the survival of the animals and haematological alterations in the peripheral blood of Swiss albino mice. MATERIALS AND METHODS Animals. Male Swiss albino mice (Mus musculus), 6–8 weeks old, weighing 25 ± 2 g from an inbred colony were used for the present study. Animals were pro- vided standard mice feed (procured from Hindustan Lever’s, Delhi) and water ad libitum. Irradiation. The cobalt teletherapy unit (ATC-C9) in the Cancer Treatment Centre, S.M.S. Medical College and Hospital Jaipur was used for irradiation. Unanaes- thetized animals were restrained in well-ventilated perspex boxes and the whole-body exposed to gamma radiation (8 Gy; at the dose-rate of 1.59 Gy/min). INTRODUCTION Radiation-induced haematological alterations have been studied extensively. After whole body exposure, mani- festations of injury to mammalian tissues are well re- flected in the peripheral blood (Rugh and Somogyi, 1968; Kumar et al., 1984; Shaheen and Hassan, 1991). The quantitative effects of whole-body irradiation are more significant than qualitative changes in circulating cells (Block, 1976). Recently, interest has been gener- ated in developing potential drugs of plant origin for modification of radiation effects. Plant extracts such as garlic (Gupta, 1988), Panax ginseng (Pande et al., 1998), Ocimum sanctum (Uma Devi et al., 2000), Spirulina fusiformis (Kumar et al., 2002) and herbal drug prepa- rations such as Liv. 52 (Saini et al., 1985; Daga et al., 1995) and rasayanas (Praveen Kumar et al., 1999) have been found to have radioprotective effects. Plant prod- ucts appear to have an advantage over synthetic com- pounds in terms of low/no toxicity at the effective dose and have minimum/no side effects. Mentha piperita (Linn.) commonly known as pepper- mint, belonging to the family Labiatae is considered aromatic, stimulant and carminative. It is used for allaying nausea, flatulence and vomiting (The Wealth