Extraction and quantitation of total peptides and proteins from the whole plant Crotalaria pallida and determination of antimicrobial activity of the isolated peptides and proteins

Abstract

Crotalaria pallida belongs to the family ‘liguminosae’ and has been used for treating various diseases. In traditional medicine, the plant is used to treat urinary problems and fever. In addition, a poultice of the roots is also applied to swelling of joints and an extract of the leaves is used to expel intestinal worms. In general, plants of liguminosae family contain peptides and proteins to protect themselves against microbial pathogens. The objective of this study was to extract and quantify peptides and proteins from Crotalaria pallida and investigate antimicrobial activity of this extracted peptides and proteins. A cold extraction buffer was used for the extraction of peptides and proteins and for quantitative determination different analytical methods were applied such as Lowry method, fluorescence spectroscopy, UV-Vis spectroscopy and enzymatic method. BSA was used as the standard protein. The concentrations calculated by different methods were in close proximity (Lowry method: 217 ± 5 μg/mL; fluorescence spectroscopy: 219 ± 3 μg/mL; UV-Vis spectroscopy: 226 ± 4 μg/mL; enzymatic method: 204 ± 3 μg\mL). The antimicrobial activity of the peptides and proteins extract was observed against two gram positive bacterial strains, Staphylococcus aureus & Bacillus subtilis and two gram negative bacterial strains, Escherichia coli & Vibrio cholera by disc diffusion method. Kanamycin 30, Amoxicillin 10 and Streptomycin 10 were used as standard antibacterial agents. Kanamycin 30 and Streptomycin 10 showed inhibition against Escherichia coli only whereas Amoxicillin 10 showed inhibition against Staphylococcus aureus. No inhibition was observed in other strains of bacteria by the standard antibacterial agents which might be due to the resistance of the strains to the agents. However no zone of inhibition was found against the four experimental species by the extract of peptides and proteins also.