Lignin is an abundant, renewable biopolymer, but its structural complexity and low reactivity have hindered its effective valorization. Herein, we report an integrated strategy combining depolymerization, demethylation, and phenolation of lignin in an acidic lithium bromide molten salt hydrate system. Spectroscopic analyses (FTIR, 1H NMR, and 2D-HSQC NMR) confirmed efficient cleavage of major ether linkages, yielding structurally simplified lignin derivatives with enhanced functionalities. Demethylation increased phenolic hydroxyl (Ar-OH) content by 1.36-2.49 mmol/g, while subsequent phenolation further elevated Ar-OH levels to 6.77-7.71 mmol/g, more than doubling those of native lignin. These structural changes translated into enhanced bioactivity: The modified lignins exhibited strong antioxidant activity (>90% DPPH⋅ scavenging), high antimicrobial efficacy (>87% bacterial inhibition), and favorable safety profiles (IC50  > 80 mg/L). In vivo feeding trials demonstrated that the modified lignins significantly improved growth performance and provided robust antiviral protection in mice. Overall, this integrated strategy enables efficient conversion of technical lignin into high-value bioactive polyphenols with performance comparable to or exceeding commercial tannins, while retaining clear economic advantages, highlighting their potential for sustainable applications in feed additives, cosmeceuticals, and nutraceuticals.

Lignin, a renewable natural antioxidant and bacteriostat, holds promise as a versatile, cost-effective feed additive. However, traditional industrial lignin faces limitations, including low reactivity, poor uniformity, and unstable properties, necessitating chemical modification. Complex modification methods pose economic and toxicity challenges, so this study adopted a relatively simple alkali-catalyzed phenolization approach, using phenol, catechol, and pyrogallol to modify kraft lignin, and characterized the resulting products using various techniques. Subsequently, their antioxidant, antibacterial, adsorption properties for heavy metal ions and mycotoxins, growth-promoting properties, and antiviral abilities were assessed. The phenolation process led to lignin depolymerization and a notable increase in phenolic hydroxyl content, particularly in pyrogallolphenolated lignin (Py-L), rising from 3.08 to 4.68 mmol/g. These modified lignins exhibited enhanced antioxidant activity, with over 99 % inhibition against E. coli and S. aureus, and remarkable adsorption capacities for heavy metal ions and mycotoxins. Importantly, Py-L improved the growth performance of mice and reduced influenza mortality. Furthermore, density functional theory calculations elucidated the mechanism behind the enhanced antioxidant properties. This study presents a promising avenue for developing versatile feed additives to address challenges related to animal feed antioxidant supplementation, bacterial control, and growth promotion.

To improve the reactivity and enrich the functionality of lignin for valorization, kraft lignin was depolymerized and demethylated via cleaving aryl and alkyl ether bonds in acidic lithium bromide trihydrate (∼60% LiBr aqueous solution). It was found that the cleavage of the ether bonds followed the order of β-O-4 ether > aryl alkyl ether in phenylcoumaran > dialkyl ether in resinol > methoxyl (MeO). The depolymerization via β-O-4 cleavage occurred under mild conditions (e.g., <0.5 M HCl at 110 °C), while sufficient demethylation of the lignin needed harsher conditions (>1.5 M HCl). Both depolymerization and demethylation generated new aromatic hydroxyl (ArOH). With 2.4 M HCl, MeO content dropped from 4.85 to 0.95 mmol/g lignin, and ArOH content increased from 2.78 to 5.09 mmol/g lignin. The depolymerized and demethylated kraft lignin showed excellent antioxidant activity and Cr(VI)-scavenging capacity, compared with original kraft lignin and tannins.

A series of novel 2H,4H-dihydro-pyrano[2,3-c]pyrazoles and 1H,4H-dihydro-pyrano-[2,3-c]pyrazoles were synthesized with aromatic aldehydes obtained from lignin and in vitro antioxidant using microwave-assisted technology and cytotoxic activities of these compounds were evaluated. The structure activity relationship (SAR) studies showed that the introduction of methoxy group in aromatic groups of dihydro-pyrano[2,3-c]pyrazoles could significantly increase their radical scavenging activities and the substituted moieties at N or C-3 position of dihydro-pyrano[2,3-c]pyrazoles could potentially influence on their antioxidant activities. Compared to positive drug control, syringyl (4-hydroxy-3,5-dimethoxyphenyl) substituted 2H,4H-dihydro-pyrano-[2,3-c]-pyrazoles 6a, 6d, 6g, 6j and 1H,4H-dihydro-pyrano-[2,3-c]pyrazoles 7a, 7d, 7g have much better antioxidant activity. In addition, all of those compounds showed low cytotoxicity through cytotoxicity evaluation. Thus, these compounds might have potential as promising agents for curing some free radical-related diseases or food additives.

Cardanol, as one of components of cashew nut shell liquid (CNSL), is a mixture of 3-n-pentadecylphenol, 3-(pentadeca-8-enyl)phenol, 3-(pentadeca-8,11-dienyl)phenol and 3-(pentadeca-8,11,14-trienyl)phenol. It has both the characteristics of phenolic compounds and flexibility of aliphatic compounds. As a versatile industrial raw materials, it has been widely used as modifiers of the phenolic resin, rubber plasticizers, coatings and adhesives etc. Specially, cardanol-based surfactants have been reported using with long-chain alkyl moieties as lipophilic group in recent years. Herein, the application of this natural and renewable material to both academic and industrial research of cardanol-based surfactants will be discussed.