Purification and characterization of lectin from the rizomes of curcuma longa linn.

Abstract

A lectin was purified from the rhizomes of turmeric (Curcuma longa L.) by aqueous extraction, precipitation with 80% saturation ammonium sulfate, and affinity chromatography on ConA Sepharose with Methyl-α-D-glucopyranoside mediated elution. The enriched preparation had a specific activity of 64,566 HU/mg protein for a yield of 41.2% total protein. The molecular weight of this lectin was estimated by SDS-15% (w/v) PAGE to be 17.3 kDa. It has hemagglutinating activity against human blood group B, as well as rabbit, mouse, rat, guinea pig, geese and sheep erythrocytes, but no such activity was detected against human blood groups A, AB and O. The pH optimum of this lectin’s hemagglutination activity is between pH 6-7, and it is stable up to 40 degree of celcius but is totally inactivated after exposure to 70 degree of celcius for 30 min. The hemagglutination activity was stimulated by Ca[superscript 2+] and Mn[superscript 2+]at less than 50 mM, but not by Mg[superscript 2+], Fe[superscript 3+], Hg[superscript 2+], Co[superscript 2+] and EDTA. The amino acid sequence of an internal fragment of this purified C. longa rhizomal lectin had a similarity to the sequence of the phytohemagglutinin precursor from the plant legume lectin family. The purified C. longa lectin, at a concentration of 47 and 94 µg/0.3 cm[superscript 2] disc showed antifungal activity against Exserohilum turicicum, Fusarium oxysporum and Colectrotrichum cassiicola. The lowest to highest minimal inhibitory concentration (MIC) values of 0.002, 0.005, 0.011, 0.09 and 0.046 mg/ml were obtained against the four bacterial species, P. aeruginosa, S. aureus, B. subtilis, and E. coli, plus the yeast C. albicans, respectively, for the purified lectin preparation, along with a high alpha-glucosidase inhibitory activity with an IC[subscript 50] of 8 µg/ml