Background: Ricinus communis (Euphorbiaceae) has previously been reported to possess analgesic, antihistamine, antioxidant and anti-inflammatory activities. This study was designed for isolation, characterization and evaluation of antibacterial and anti-proliferative activities of R. communis seed protein.
Methods: The concentration and molecular weight of R. communis seed protein were estimated by SDS-PAGE and spectrophotometric analysis, respectively. Lectin activity was evaluated by hemagglutination assay on mice blood. In vitro susceptibility of four human pathogenic bacteria including Escherichia coli, Pseudomonas aeruginosa, Enterobacter aerogenes and Staphylococcus aureus was detected using disk diffusion assay, and minimum inhibitory concentration (MIC) value was determined using micro-dilution method. A total of twenty four Swiss albino mice containing Ehrlich's ascites carcinoma (EAC) cells were treated with the crude protein of R. communis at 50 and 100 μg/ml/d/mouse for 6 days. Growth inhibitory activity of R. communis seed protein on EAC cells was determined by haemocytometer counting using trypan blue dye and DAPI (4΄,6-diamidino-2-phenylindole) staining was used to assess apoptotic cells.
Results: The protein concentration of six R. communis (castor) varieties ranged between 21-35 mg/ml and molecular weight between 14-200 kDa. Castor protein agglutinated mice blood at 3.125 μg/wall. The seed protein shows considerable antimicrobial activity against E. coli, P. aeruginosa and S. aureus, exhibiting MIC values of 250, 125 and 62.5 μg/ml, respectively. Administration of seed protein led to 54 % growth inhibition of EAC cells at 100 μg/ml. DAPI staining indicates marked features of apoptosis including condensation of cytoplasm, nuclear fragmentation and aggregation of apoptotic bodies etc.
Conclusion: Our study suggests that the lectin rich R. communis seed protein has strong antibacterial and anticancer activities.
Keywords: Apoptosis; Castor bean; Disc diffusion; EAC cells; Lectin; MIC; Mice; Protein.