Antimicrobial, antioxidant and antiproliferative activities of a galactose-binding seed lectin from Manilkara zapota

A seed lectin from Manilkara zapota (MZSL) was purified using ammonium sulphate precipitation and affinity chromatography. Hemagglutination activity, neutral sugar content and physicochemical properties of the lectin were determined and toxicity was checked by brine shrimp toxicity assay. Antimicrobial, antioxidant as well as in vitro anticancer activities of MZSL were also evaluated. Our findings showed the molecular weight of MZSL to be 33.0 +/- 1 kDa. Minimum hemagglutination concentration of the lectin was 15.625 mu g/ml. With a neutral sugar content of 6.32 %, the lectin was fully active at a temperature range of 30-50 degrees C and pH 7.0-8.0 and it was mildly toxic with an LC50 value of 107.93 mu g/ml. The lectin demonstrated bacteriostatic activity against gram-positive bacteria in contrast to gram-negative bacteria at a concentration of 31.25 mu g/ml, agglutinated Staphylococcus aureus and Shigella dysenteriae and exerted fungistatic activity against Aspergillus niger. MZSL dose-dependently reduced the formation of biofilm by E. coli. DPPH assay confirmed its antioxidant activity with an IC50 value of 96.42 mu g/ml. MZSL showed 21.64 % growth inhibition against Ehrlich ascites carcinoma (EAC) cells at 80 mu g/ml whereas its antiproliferative potential against MCF-7 and A-549 cancer cell lines became evident with IC50 values of 70.66 mu g/ml and 107.64 mu g/ml, respectively.