Antifungal and Antiproliferative Activities of Lectin from the Rhizomes of Curcuma amarissima Roscoe

A lectin was purified from the rhizomes of Curcuma amarissima Roscoe by aqueous extraction, fractionation with 80% saturated ammonium sulfate, and a combination of affinity and gel chromatography on ConA Sepharose and Superdex G-75, respectively. The molecular mass of the purified lectin was 32.4 kDa, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The lectin showed no significant specificity in its ability to hemagglutinate erythrocytes from human blood groups (A, B, AB, and O), but for other animals, it only agglutinated rabbit and rat, and not mouse, guinea pig, goose, and sheep erythrocytes. The lectin was stable at temperatures below 40A degrees C, but the hemagglutinating activity halved when it was heated to 45-85A degrees C and was completely lost at 95A degrees C. The hemagglutinating activity was more stable at 80A degrees C than at 70A degrees C and was rapidly inactivated at 90A degrees C. It showed a maximum hemagglutination activity within the pH range of 8.0-11.0. The deduced amino acid sequence of an internal tryptic peptide sequence of this purified lectin showed sequence similarity (homology) to other members of the leucoagglutinating phytohemagglutinin precursor family, whilst the complete lectin inhibited the in vitro growth of three plant pathogenic fungi, Fusarium oxysporum, Exserohilum turicicum, and Colectrotrichum cassiicola, at a concentration of 17.5 to 35 A mu g, and showed in vitro cytotoxicity against the BT474 breast cancer cell line with an IC50 of approximately 21.2 mu g.