Influence of aqueous crude extracts of medicinal plants on the osmotic stability of human erythrocytes Mariana V. de Freitas a , Rita de Ca ´ssia M. Netto a , Juliana C. da Costa Huss a , Tatiana Maria T. de Souza a , Ju ´nia O. Costa a , Cynthia B. Firmino b , Nilson Penha-Silva a, * a Institute of Genetics and Biochemistry, Federal University of Uberla ˆndia, Uberla ˆndia, MG, Brazil b Health Technical School, Federal University of Uberla ˆndia, Uberla ˆndia, MG, Brazil Received 23 May 2007; accepted 30 July 2007 Available online 10 August 2007 Abstract This work analyzed the effects of the aqueous crude extracts of Artemisia absinthium L., Lippia sp., Bryophyllum sp., Solidago micro- glossa DC, Cymbopogon citratus DC and Mentha x villosa HUDSON on the osmotic stability of human erythrocytes. Hemolysis was monitored by measurement of absorbance at 540 nm following addition of erythrocytes to NaCl solutions of varying concentration. Absorbance was fitted to sigmoid regression curves given by the Boltzmann equation, and hemolysis was characterized by the NaCl con- centration leading to lysis of 50% of cells (H 50 ), and by the intensity (H) and the amplitude (dS) of the lysis effect. The parameters were determined in the absence and presence of the crude extracts. The extracts of Artemisia absinthium, Lippia sp., C. citratus and M. villosa protected human erythrocytes against hypotonic shock, as evidenced by a decrease in the values of H and H 50 compared to the control solution (p < 0.05). The extracts of Bryophyllum sp. and S. microglossa enhanced hemolysis, since their H 50 values were higher than in the control group (p < 0.05), but they also showed protective effects, as evidenced by a decrease in H and an increase in dS. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Erythrocytes; Hematotoxicity; Medicinal plants; Membrane stability 1. Introduction Cell membranes must combine the opposing properties of fluidity and stability in order to function effectively (Cri- bier et al., 1993). A degree of fluidity is essential to allow signalling and transport. However, excessive fluidity can compromise stability and vice versa. Membrane stability represents the capacity of this biological complex to main- tain its structure under chaotropic conditions such as oxidative stress (Van-Ginkel and Sevanian, 1994), hypoto- nicity, pH extremes, heat and the presence of solutes (such as ethanol, urea and guanidine) (Timasheff, 1998). Many natural products present in medicinal plants can affect biological membranes (Sharma and Sharma, 2001). The effects may be positive, for example, through restora- tion of fluidity that would otherwise tend to decrease with ageing (Penha-Silva et al., 2007). The effects may also be negative, however, through promotion of excessive fluidity or denaturation of the membranes. Erythrocytes represent a good model for the study of membrane stability since their lysis releases the protein hemoglobin which can be readily measured spectrophoto- metrically. The osmotic stability of erythrocytes correlates with their resistance to lysis in response to variation in sol- vent tonicity and can be determined by measurement of hemoglobin release after a fixed period of incubation of blood in water solutions with decreasing concentrations of NaCl (Jain, 1973). Evaluation of membrane stability during exposure to phytotherapeutic products must be routinely considered in their evaluation, since the consumption of these products is increasing globally (Willcox et al., 2004), and could 0887-2333/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.tiv.2007.07.010 * Corresponding author. Tel.: +55 34 3218 2203x23; fax: +55 34 3218 2203x24. E-mail address: nspenha@ufu.br (N. Penha-Silva). www.elsevier.com/locate/toxinvit Available online at www.sciencedirect.com Toxicology in Vitro 22 (2008) 219–224