Isolation of Lectin from Opuntia ficus-indica Cladodes

Lectins are hemagglutinating proteins with carbohydrate binding sites; these proteins have biological properties including antimicrobial activity. The aims of this work were the isolation of Opuntia ficus-indica lectin (OfiL) and evaluation of its antifungal activity. Hemagglutinating activity (HA) of cladode crude extract (CE20%) was evaluated using rabbit, chicken or human erythrocytes. The HA assay was also made in presence of carbohydrates or ions and at different temperatures and pH values. OfiL was isolated by chromatography of CE20% on chitin or Sephadex G-25 columns. OfiL was submitted to polyacrylamide gel electrophoresis for denatured proteins (SDS-PAGE). CE20% and OfiL were evaluated for antifungal activity using Colletotrichum gloeosporioides, Candida albicans, Fusarium descencelulare, F. lateritium, F. moniliforme, F. oxysporum and F. solani. CE20% HA was detected with rabbit, chicken and human erythrocytes, A and O types. The HA was high at pH 5.0, thermostable, inhibited by glycoproteins and stimulated with Ca2+ or Mg2+. OfiL purified by chitin (13 folds) as well as by Sephadex G-25 (10 folds) columns was resolved as single 8.4 kDa polypeptide by SDS-PAGE. CE20% and OfiL showed antifungal activity against all tested fungi. The lectin was mainly active on C. albicans. The inhibition of HA with glycoproteins revealed that activity of O. ficus indica cladodes is due to lectin presence. Antifungal activity from extract and OfiL indicates cladode biotechnological potential.