Evaluation of Therapeutic Properties of Lignins Extracted from Cauliflower Wastes for Their Potent Valorization Through Sustainable Approach

Abstract

Heterogeneous supramolecular structures of waste feedstock mainly, lignin has profound biological, therapeutic and industrial applications. The separation of lignin is greatly hindered by the rigid and compact structure of lignocellulosic biomass. The present study highlighted the maximum amount of lignin recovered from cauliflower wastes by two different extraction methods, which are the conventional alkaline extraction method and a novel experimental catalytic hydrothermal pretreatment method. The yield of lignin extracted from the alkali pretreated (Ak-L) and catalyst assisted hydrothermally pretreated (HT-L) cauliflower wastes was much higher than that of lignin obtained from untreated CW. Optimization of alkali and catalyst concentrations, residence time, and incubation temperature for the maximum recovery of lignin was conducted. FTIR spectral region of Ak-L and HT-L from 1736 to 1402 cm−1 demonstrated the presence of aromatic skeletal vibration and conjugated groups due to syringyl and guaicyl groups. All lignin fractions exhibited higher DPPH and ABTS radical scavenging activities and also higher Fe2+ chelating activity and FRAP assay. Both Ak-L and HT-L fractions had potential antimicrobial and cytotoxic activities. HPLC revealed the presence of ferulic acid, gallic acid, trans-cinnamic acid as antimicrobial compounds. The results of comprehensive structural analysis and antioxidant property of the extracted lignin presented in this study demonstrated the potential of cauliflower wastes to serve as the source of lignin and consequently lignin based valuable products of industrial importance. More sustained research work will be imperative to understand the chemical mechanisms involved in the antioxidant, antimicrobial and cytotoxic effects of the lignin extracts. Cauliflower wastes were pretreated with two different methods for extraction of lignin and the extracted lignins were studied for its therapeutic properties