Extraction of Nanocrystalline Cellulose from Biomass and its Dissolution in Pyridinium-based Ionic Liquid for Antioxidant and Antimicrobial Applications

Abstract

Pakistan being a populated and agricultural country has a problem of massive organic waste production and disposal. Due to the large amounts of organic waste, environmental issues are becoming pressing. These concerns have increased interest in the environmental-friendly synthesis of chemicals and value-added goods from biomass waste. Owing to distinctive qualities such as high surface area, customizable surface chemistry, outstanding mechanical strength, biodegradability, and renewable nature, nanocellulose (NC) has recently received a lot of attention. However, its applications are restricted due to its poor solubility. This work produces a green solvent for dissolution ofNC extracted from eucalyptus bark. Nanocellulose (NC) was extracted from hardwood of Eucalyptus camaldulensis by a new extraction method and confirmed by XRD, FTIR, and SEM analysis. XRD confirmed nanocellulose as nanocellulose type I with 71 % degree of crystallinity. Zeta sizer provided that particle size of nanocellulose is 172 nm and zeta potential analysis showed the presence of bonded OH groups on the surface ofnanocellulose. A newly derivatized ter-butyl Pyridinium chloride ionic liquid [C4Py] [Cl](PyIL) was synthesized for NC dissolution and was characterized by NMR, FTIR, and UV analysis. The highest value for the refractive index, density and viscosity of PyIL evaluated at 20°C is 1.5312, 1.69 gcm-3 , and 10.04 Pa. s respectively. In vitro antibacterial activity of ionic liquid (IL) anp cellulose dissolve ionic liquid (CIL) was investigated by an agar well diffusion assay against pathogenic bacteria (Escherichia coli, Staphylococcus Aureus, Klebsiella pneumoniae, and Bacillus subtilis), that causes various diseases, to scrutinize the in vitro antibacterial activity of the IL and CIL. 1,1 -diphenyl-2-picrylhydrazyl (DPPH) radical scavenging effect and FRAP assay were used to scrutinize the antioxidative activities of nanocellulose (NC), ter-butyl pyridinium chloride (PyIL), and cellulose dissolved ionic liquid. The best activity was shown by CIL giving 59% radical scavenging at ICso of 24.43 ~L against DPPH and giving 560 ~LlmL ascorbic acid equivalent per mg of sample. The interaction of NC with PyIL was investigated at DFT/B3L YP/6-31G (d, p) level using Gaussian 09 program. Frontier molecular orbital analysis and global reactivity parameters were computed for determination of stability and reactivity ofNC and PyIL before and after interaction. In the light of experimental and theoretical results, it was determined that reactivity, antimicrobial and antioxidant properties of NC increase upon dissolution in PyIL. Thus, in this study nanocellulose (NC) is not only extracted efficiently from hardwood of Eucalyptus by novel method, but the synthesis of green solvent, tertiary butyl pyridinium chloride ionic liquid (PyIL), for their dissolution made them more applicable for various applications specially in medicine.