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Technical lignins, mostly generated as byproducts from the pulping industry, are highly abundant aromatic sources. However, they are underutilized due to their complexity, as well as structural alteration during chemical pulping processes. In-depth elucidation of technical lignins is becoming essential for their valorization in view of the lack of understanding of technical lignin structures. In this work, alkaline and kraft lignins were prepared and comparatively characterized by 2D HSQC NMR. By applying authenticated reference compounds, the phenylglycerol structures, characteristic of the cleavage of nonphenolic β-aryl ether by soda pulping, in the alkaline lignin were identified and quantified by 2D HSQC NMR. Phenylglycerol structures in alkaline lignin were estimated to be 8–14%, which was much higher than that in kraft lignin. This finding was supported by the results from model studies; i.e., the yield of the phenylglycerol product was 40% that obtained from the soda pulping treatment of a nonphenolic β-aryl ether compound while the yield of that from kraft treatment was lower than 5%. In addition, styryl ether structures from phenolic β-aryl ethers of alkaline lignin were also revealed by 2D NMR. These new findings will benefit the mechanistic understanding of lignin reactions and structural elucidation of technical lignins, which will provide useful information (or new insights) for the development of lignin valorization strategies.

Oral drug delivery is a common route for management of inflammatory bowel disease (IBD) but suffers from low bioavailability and systemic side effects during passage through the alimentary canal. Here, we present a therapeutic nano reagent of a ferulic acid-derived lignin nanoparticle (FALNP). We showed that FALNP with favorable antioxidant activity can regulate IBD. More importantly, the intestinal pH-responsive degradability of FALNP allows it to withstand the harsh gastric acid environment, bypass physiological barriers, and target the intestine for gastrointestinal delivery. In vivoexperiments showed that oral administration of FALNP markedly relieved pathological symptoms in a mouse model of acute colitis by reducing oxidative stress and regulating the gut microbiome. By integrating anti-inflammatory medicine, FALNP also can be used as a bioactive carrier to exert a potent synergistic therapeutic effect. In addition to colitis, FALNP can be readily adaptable for use as a carrier platform for therapy of many other intestinal diseases.