Highly regioselective enzymatic synthesis of lutein-3-monoesters

Novozym 435: the “perfect” lipase immobilized biocatalyst?

“…The regioselective synthesis of 3-Oacyl monoester lutein using N435 and vinyl propionate or vinyl stearate as activated acyl donors has been also successfully reported. 352 N435 was found to be the most efficient lipase to catalyze the production of Agave fructans mono-and diacylated with lauric acid via a transesterification reaction. 353 1,3-Di-O-benzyl-myo-inositol was selectively acetylated using vinyl acetate.…”

Utilization of Plant-Based Wastes for a Sustainable Preparation of Xanthophyll Esters via Acid Anhydrides Using β-Pinene as a Bio-Derived Solvent

“…At 40 °C and at ambient temperature, the reaction rates were lower, but yields remained stable and quantitative even after 24 h. In other studies, reactions were most often carried out at ambient temperatures (20−25 °C) or at 40 °C. 16,19,27,28,33,36,37 In some instances, higher temperatures were also used (50−90 °C), but surprisingly, no diester product degradation was reported. [20][21][22]32,35 We show that ambient temperature is the most energy-efficient option which ensures good yields with concomitant product stability.…”

“…16,20,46,47 Only in certain regioselective syntheses where monoesters of dihydroxyxanthophylls were targeted were the relations between the main and side products explicitly given. 17,19,28,29 The synthesized products (xanthophyll esters in the all-E configuration) were also purified by using LLE and SPE, respectively (Table S2). The latter proved especially efficient and versatile as all products were obtained with a minimum purity of 74% (median 96%).…”

“…Reaction conditions used were mild enough to enable the conservation of labile epoxide moieties in violaxanthin, as evidenced by MS, UV, and HPTLC data for all 11 violaxanthin esters (Figure S8). Comparisons with the known literature regarding side-product formation are difficult since these are rarely quantified and reported; in general, xanthophyll diester in the all- E configuration is assumed as a single product (or an all- E monoester in the case of monohydroxyxanthophylls). ,,, Only in certain regioselective syntheses where monoesters of dihydroxyxanthophylls were targeted were the relations between the main and side products explicitly given. ,,, The synthesized products (xanthophyll esters in the all- E configuration) were also purified by using LLE and SPE, respectively (Table S2). The latter proved especially efficient and versatile as all products were obtained with a minimum purity of 74% (median 96%).…”

“…The biological role of such esterification is still not completely understood, but it is assumed that this process enhances the chemical stability of the core carotenoid and also facilitates its migration from ruptured chloroplasts into chromoplasts. , In a laboratory setting, xanthophyll esters have so far been synthesized with intent to (i) enable their structural elucidation, (ii) alter the xanthophyll’s pharmacokinetic properties, (iii) increase their stability and water solubility, and (iv) prepare standard reference materials for quantitative analysis of these pigments in natural materials. , Carotenoids, including hydroxylated xanthophylls, are well known for their instability when exposed to light, oxidants, acids, elevated temperatures, or metals, even in trace amounts. , This inherent property sets xanthophylls apart from most alcohols and introduces complexity to any of their transformations, even to such a simple reaction as esterification. Moreover, reactivity of different xanthophylls was shown to vary under otherwise identical experimental conditions, making the development of a universal synthetic approach quite challenging. ,, For a comprehensive review on esterification strategies and functionalities of xanthophyll esters, the reader is directed to a recent monograph by Nagy et al Enzyme-catalyzed esterification with immobilized lipases could be considered as the current state of the art in the field, but application of hazardous organic solvents (tetrahydrofuran, toluene, and n -hexane), long reaction times, elevated temperatures, and low reaction yields render this seemingly green approach impractical for a more general utilization. − To the best of our knowledge, not only those involving enzymatic catalysis, but in general, none of the known synthetic pathways to xanthophyll esters is environmentally friendly and economically viable on an industrial scale . Many are (i) energetically nonefficient (heating up to 90 °C); , (ii) all employ halogenated, aromatic, or other solvents and chemicals which are hazardous to the environment and to human health and which cannot be easily recycled; (iii) they generate large amounts of waste; (iv) many degradation, isomerization, and other side reactions are often taking place, resulting in poor yields of the esterification reactions; ,,− and last, (v) they do not use renewable feedstocks, which is especially problematic in light of economic and environmental sustainability.…”