Novel method for extraction of lignin from Pinus roxburghii (PR) needles and its application for antimicrobial lignin-silver composite synthesis

Due to the easy proliferation of microbes on different surfaces, fundamental studies are being performed globally to replace the older methods with new ones that provide better potency to the antimicrobials and are environmental-friendly. The present study focuses on the extraction of lignin, from Pinus roxburghii leaves and subsequently using the same for the synthesis of lignin silver composites. For achieving the same the dried fallen needles were collected, grinded to powder, and subjected to treatment with acetic acid, formic acid and water using different ratios and at different temperatures following a novel method for the extraction of lignin. The extracted lignin was characterised by various techniques such as FTIR, 1H NMR, 13C NMR and HRMS to get evidence of successful extraction with excellent purity. Two lignin-silver composite bio-films were synthesized with one having guar gum and other with agar. The films were subjected to the anti-microbial studies against gram-positive (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli). The results indicate enhanced antimicrobial activity of the composites than the precursor lignin and these have high potential for use in wound dressing and healing applications.