Soluble laticifer proteins from Calotropis procera as an effective candidates for antimicrobial therapeutics

Calotropis procera is a latex-producing plant with plenty of pharmacologically active compounds. The principal motivation behind this study was to separate and characterize laticifer proteins to check their antimicrobial potential. Laticifer proteins were separated by gel filtration chromatography (GFC) and investigated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The SDS-PAGE assay detected proteins of molecular weights of 10 to 30 kDa but most of them were in the range of 25 to 30 kDa. The soluble laticifer proteins (SLPs) were tested against Gram-positive bacteria i.e., Streptococcus pyogenes and Staphylococcus aureus whereas Escherichia coli and Pseudomonas aeruginosa were tested as Gram-negative bacteria, we determined a profound anti-bacterial activity of these proteins. In addition, SLPs were also investigated against Candida albicans via the agar disc diffusion method which also showed significant anti-fungal activity. SLP exhibited antibacterial activity against P. aeruginosa, E. coli, and S. aureus with a minimum inhibitory concentration (MIC) of 2.5 mg/mL for each, while MIC was found at 0.625 mg/mL for S. pyogenes and 1.25 mg/mL for C. albicans. Moreover, enzymatic activity evaluation of SLP showed the proteolytic nature of these proteins, and this proteolytic activity was greatly enhanced after reduction which might be due to the presence of cysteine residues in the protein structure. The activity of the SLPs obtained from the latex of C. procera can be associated with the involvement of enzymes either proteases or, protease inhibitors and/or peptides.