Abstract
Chlorophylls and their derivatives have been extensively studied due to their unique and valuable properties, including their anti-mutagenic and anti-carcinogenic features. Nevertheless, high-purity-level chlorophylls extracted from natural sources are quite expensive because the methods used for their extraction have low selectivity and result in low yields. This study aimed to develop a “greener” and cost-effective technology for the extraction of chlorophylls from biomass using aqueous solutions of ionic liquids (ILs). Several aqueous solutions of ILs, with hydrotropic and surface-active effects were evaluated, demonstrating that aqueous solutions of surface-active ILs are enhanced solvents for the extraction of chlorophylls from spinach leaves. Operating conditions, such as the IL concentration and solid–liquid ratio, were optimized by a response surface methodology. Outstanding extraction yields (0.104 and 0.022 wt.% for chlorophyll a and b, respectively, obtained simultaneously) and selectivity (chlorophyll a/b ratio of 4.79) were obtained with aqueous solutions of hexadecylpyridinium chloride ([C16py]Cl) at moderate conditions of temperature and time. These extraction yields are similar to those obtained with pure ethanol. However, the chlorophyll a/b ratio achieved with the IL aqueous solution is higher than with pure ethanol (3.92), reinforcing the higher selectivity afforded by IL aqueous solutions as viable replacements to volatile organic compounds and allowing the obtainment of more pure compounds. Finally, the recovery and reuse of the solvent were evaluated by using a back-extraction step of chlorophylls using ethyl acetate. The results disclosed here bring new perspectives into the design of new approaches for the selective extraction of chlorophylls from biomass using aqueous solutions of surface-active ILs.
Highlights
Chlorophylls are the main photoreceptors in photosynthesis and common are in nature; they are found in plants, algae and cyanobacteria [1]
Taking into account the valuable properties of chlorophylls as well as the advantages of ionic liquids (ILs), we propose here the use of IL aqueous solutions as alternative solvents for the extraction of chlorophylls from spinach leaves by solid–liquid extraction at moderate temperature and time
The same operating conditions were kept in all experiments, namely the IL concentration at 10 wt.%, a spinach-solvent weight fraction ratio of 1:50 (solid–liquid ing hydrophobic solutes in the micelle core, being ◦usually more pronounced at low conratio (R) = 0.02) and an extraction time of 30 min at 25 C
Summary
Chlorophylls are the main photoreceptors in photosynthesis and common are in nature; they are found in plants, algae and cyanobacteria [1]. Two chemical forms can be distinguished, namely chlorophyll a and b, usually present at a ratio of 3:1 [2]. Several studies have demonstrated the positive effects of natural pigments in human health [5]. Chlorophylls have been described as presenting antimutagenic and anti-carcinogenic properties due to their ability to accumulate in tumor tissues and to cause a photodynamic effect under laser radiation, producing reactive oxygen species and resulting in cancer cell death [6].
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