Non-aqueous lyotropic liquid crystalline phases of natural surfactant Withania somnifera for antibacterial applications

Abstract

Lyotropic liquid crystalline (LLC) phases are derived from a binary mixture of Withania somnifera roots and ethylene glycol. Studied concentrations of Withania somnifera roots/ethylene glycol are 2:98, 5:95, 10:90, 20:80 and 30:70 wt/wt%. The nematic lyotropic phase is obtained for all the concentrations examined under polarising optical microscopy (POM). The formation of a lyotropic phase in these systems could be explained by considering hydrogen bonding between amphiphilic molecules (Withanolides) and solvent (-OH groups). Nematic lyotropic phases are further tested for antibacterial activity against gram-positive (Bacillus subtilis) and gram-negative (Pseudomonas stutzeri) bacteria. The LLCs show strong inhibition of approximately 2-3 times higher than that of the standard antibiotic (Streptomycin) for gram-positive bacteria Bacillus subtilis. It is noted that the concentration of the binary mixture shows a strong effect on the inhibition of the bacteria irrespective of the nematic ordering for both bacteria.