Synthesis of peppermint oil-loaded chitosan/alginate polyelectrolyte complexes and study of their antibacterial activity

Peppermint oil contains menthol, menthone and menthofuran as major components. It finds extensive applications in food, flavoring and pharmaceutical industries. However, it gets readily oxidised when exposed to air or ultraviolet light and is highly volatile in nature. So, to mitigate these shortcomings microencapsulation of peppermint oil is often used. In the present case a chitosan/alginate polyelectrolyte complex prepared by complex coacervation method was chosen as the encapsulating material for peppermint oil. The formation of polyelectrolyte complex was found to be dependent on pH, ratio between chitosan and alginate and amount of crosslinker, glutaraldehyde. The prepared complexes were characterized by fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The swelling and release studies were carried out in buffer solutions of pH 4, 7, 9 and phosphate buffered saline system (PBS, pH = 7.4). The complexes were tested for antimicrobial activity against Proteus mirabilis, Enterobacter aerogenes, Bacillus subtilis and Staphylococcus aureus. The highest zone of inhibition (25 ± 0.5 mm) was observed against Bacillus subtilis.

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