Lectins in fruits having gastrointestinal activity: Their participation inthe hemagglutinating property of Escherichia coli 0157 : H7

Background. In fruits with therapeutic properties for antidiarrheic and lax ative uses, the presence of lectins may be the bioactive properties that in terfere with bacterial adhesion, thought to be competition for glycoside si gnal sites in the attachment. Methods. This study identifies lectins in crude extracts from fruits such a s Tamarindus indica (tamarind), Spontia vulgaris (plum), Psidium guava (gua va), Mangifera indica (mango), Cydonia vulgaris (quince), and Crataegus mex icanus (tejocote). To verify the procedures, extracts from Ricinus communis (castor bean), Glicina max (soybean), Phaseolus vulgaris (beans), Vicia fa va (fava bean), and Solanum tuberosum (potato) were used as controls for le ctin activity. Both sources of lectins were analyzed to determine their par ticipation in the host-parasite interaction, using as a model the hemagglut inating properties of Escherichia coli O157:H7 (EHA). Results. All extracts showed hemagglutination to group O erythrocytes test (HA) with the exception of mango. Two new galactose-specific lectins were i dentified from tamarind and guava. When analyzed for participation in EHA. only guava lectins inhibited this, while soybean lectin induced hemolysis; as both lectins bind to galactose, it is probable that their recognition oc curs in different domains. Sugars involved in the attachment between Escher ichia coli O157:H7 and red cells were identified and again, galactose in ad dition to mannose was found to be related in EHA. On the other hand, guava lectins also agglutinated E. coli O157:H7, perhaps due to the same galactos e-specific lectin or to another type of lectin. Conclusions. In summary, guava has a galactose-specific lectin that prevent s adhesion of E. coli O157:H7 to red cells; this lectin is mediated by gala ctose. Prevention could also be due to their capacity of agglutinating E. c oli by guava lectins. Soybean lectin induced hemolysis only when bacteria w as present, but not with floating secretions. This finding showed that guav a is a source of lectin that can be explored to prevent adhesion of E. coli to epithelial intestinal cells: contrariwise, soya must be studied to see its participation in the uremia caused during E. coli O157:H7 pathogenisis. (C) 2001 IMSS. Published by Elsevier Science Inc.