Valorization of lignins from energy crops and agro‐industrial byproducts as antioxidant and antibacterial materials

Abstract

BACKGROUND Developing eco‐friendly antioxidant and antimicrobial substances originating from biomass residues has recently attracted considerable interest. In this study, two lignosulfonates and various oxidized water‐soluble lignins were investigated for their antioxidant properties, as assessed by ABTS, DPPH and Folin–Ciocalteu methods, and their antimicrobial activity against some bacterial strains responsible for human pathologies. RESULTS The lignosulfonates showed the largest antiradical/antimicrobial capacity, whereas the other substrates were less effective. The observed antioxidant/antibacterial properties were positively correlated with lignin aromatic/phenolic content. The positive correlation between antiradical and antimicrobial activities suggests that lignin scavenging capacity was also involved in its antibacterial activity. A greater antimicrobial performance was generally observed against Gram‐positive bacterial strains, and it was attributed to the intrinsic larger susceptibility of Gram‐positive bacteria to lignin phenols. A significant though lesser inhibitory activity was also found against Escherichia coli. CONCLUSION Our results confirmed the dependence of lignin antioxidant/antibacterial power on its extraction method and chemical structure, as well as on the type of bacterial strains. Identifying the relationship between lignin molecular composition and its antioxidant/antibacterial features represents an advance on the potential future use of renewable and eco‐compatible lignin materials in nutraceutical, pharmaceutical and cosmetic sectors. © 2021 Society of Chemical Industry.

Humic substances from composted fennel residues control the inflammation induced by Helicobacter pylori infection in AGS cells

“…In line with previous studies, these data indicate a clear correlation between the phenolic content of this humic samples (Table 1 and Fig. 2) and its antioxidant capacities 4,9,40 . Although antiradical and antioxidant activities of several humic substances have been already discussed 41 , no literature information is reported regarding speci c HS isolated from composted fennel residues, which may represent an important source of bioactive material for the pharmaceutical industry 42 .…”

“…Antioxidant activity of humic extract from fennel composted vegetable wastes activity of HS-FEN was performed by ABTS assay as described elsewhere 2,9,40 Solutions of humic samples prepared at three different concentrations (25, 30,50 µg mL − 1 ) in ultrapure water. Then, 100 µl of HS of each concentration were hence added to 1.9 ml of ABTS•+ working solution.…”

Antiflammatory activity and potential dermatological applications of characterized humic acids from a lignite and a green compost

“…1 , 3 ). While previous studies pointed out that the antimicrobial activities promoted by humic and Humic‐like substances (HULIS) against plants pathogens depended on their specific molecular composition 18 , 19 , 44 , 45 , we show for the first time that HA isolated from composted agricultural biomasses exert protection properties on human cells and this depends on the molecular composition of the tested humic acid.…”

Evaluation of Sustainable Recycled Products to Increase the Production of Nutraceutical and Antibacterial Molecules in Basil Plants by a Combined Metabolomic Approach

“…The shared lower values of LigR in all extracts ( Table 1 ) underlined a close correlation of spectral intensities associated to methoxyl groups (45–60 ppm) and O-aryl-C molecules (140–160 ppm) [ 25 , 27 , 28 ]. The lowest LigR of CT-COF suggested a preferential accumulation of dissolved phenolic compounds, distinct from lignin-derived molecules, during composting processes of coffee ground wastes and their release in water extracts [ 25 , 29 ]. Conversely, the slight larger LigR ratios shown by HS-COF and CT-ART may be related to a contribution of nitrogenated molecules within the broad bands in the 40–55 ppm NMR region ( Figure 1 ) that indicate the inclusion of peptidic and amino acid moieties [ 13 ].…”

“…Different natural substances in plant tissues act as antioxidant agents in biochemical processes, providing a significant protection against various diseases related to oxidative stress induced by free radical species (RNS) and reactive oxygen species (ROS) [ 48 ]. Generally, antioxidant capacity is directly correlated with the content of phenolic compounds [ 28 , 29 , 49 ]. Therefore, the role of phenolic/quinonic components as electron donors/acceptor in plant extracts, have been extensively studied [ 50 ].…”