The use of safe and sustainable solvents able to solvate reagents and to catalyze their reactions at temperatures below 100°C is an innovative strategy to develop future lignocellulosic biorefineries. Many low-transition-temperature mixtures (LTTMs) have been investigated for this purpose. Among them, natural deep eutectic solvents (NADESs) have been proposed as cheap and renewable alternatives to ionic liquids for the synthesis of bio-based chemical building blocks. We compare herein the ability of several organic acids/choline chloride/water LTTMs to perform D-fructose dehydration to 5-hydroxymethylfurfural (5-HMF). The addition of chloride salts as well as an increased proportion of choline chloride promotes 5-HMF formation, which seems to indicate a beneficial effect of chloride anions on D-fructose dehydration. Besides improving selectivity by at least 10 %, increasing the choline chloride/acid ratio could enhance the biodegradability of the LTTMs. Unlike other acidic components, maleic and citric acids are especially selective at early D-fructose conversion. Maleic acid was the most selective acidic component among the tested chemicals, achieving an 80 % 5-HMF molar yield in 1 h at 90°C.

Honey polyphenols have been studied with the objective of relating honeys to their floral sources. Initially synthesized by plant, these polyphenols can be found in the plant’s nectar, which are collected by bees, which convert the nectar into honey. Consequently, polyphenols constitute minor components of honey. The development of a solid-phase extraction method for honey polyphenols is presented in this study. The technique employs Amberlite XAD-2 adsorbent and was tested on monofloral honeys from six different plants: acacia, chestnut, eucalyptus, thyme, sunflower, and wild carrot. Analyses were performed using high-performance liquid chromatography coupled with UV detection and mass spectrometry. Several phenolic acids and flavonoids were identified: caffeic and p-coumaric acids, quercetin, kaempferol, naringenin, chrysin, and pinocembrin. Generally, the quantity of a given polyphenol in the honey was around 0.2 mg/100 g of honey, except for chestnut honey, which contained around 3.0 mg of p-coumaric acid/100 g of honey. Analyses highlighted significant formation of cis isomers for phenolic acids during the extraction despite protection from light.

The conversion of abundant hexoses and pentoses to 5-hydroxymethylfurfural (5-HMF) and 2-furfural (2-F) is subject to intensive research in the hope of achieving competitive production of diverse materials from renewable resources.