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The generation of pseudo-lignin as byproduct during the lignocellulose acidic pretreatment has been proposed for many years. However, the detailed formation mechanism is still unclear. Moreover, there is a lack of understanding in the initial reaction during the formation of humins (byproducts in furfural production) and acid-induced hydrothermal carbon (carbon material). In this work, the initial formation of these three substances were investigated. We first found the common feature of their formation process was that carbohydrate-hydrolyzed compounds could form black polymers by condensing in acidic media, but the difference was dependent on the reaction degree. Furthermore, the results revealed that oxidation was an accelerator for condensations during producing black polymers because oxidized compounds could enhance the acidity of the reaction system. However, condensations of oxidized compounds were more difficult to proceed. Meanwhile, during the initial stage, the dominating pathway was that furfural condensed with itself and isomerized xylose via aldol-condensation.

Hemicellulose is the second most abundant plant polysaccharides after cellulose. Due to the non-toxicity, abundance and biodegradability, recently more and more attention has been focused on the exploration of hemicellulose as the potential substrate for the production of liquid fuels and other value-added chemicals and materials in different fields. Especially in the pharmaceutical and medical field, hemicellulose currently has aroused growing concern in immune regulation, bacteria inhibition, drug release, anti-caries, scaffold materials and anti-tumor because of its unique special physiological characteristics including biocompatibility, inhibiting cell mutation and anti-cancer effect, etc. In this paper, we introduce the application of nature hemicellulose, its degradation products, its derivatives and hemicellulose-based materials in the medical field. Their properties and use effects are also discussed in detail. Moreover, the extraction technologies of nature hemicelluloses, the preparation of hemicellulose-derived products are reviewed here briefly. The recent trends and perspectives of future development are highlighted.

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