A Simple and Efficient Method for the Partial Synthesis of Pure (3R,3'S)-Astaxanthin from (3R,3'R,6'R)-Lutein and Lutein Esters via (3R,3'S)-Zeaxanthin and Theoretical Study of Their Formation Mechanisms.

Eloy Rodríguez-Deleón,José Báez,J Jiménez-Halla,M Bah

doi:10.3390/molecules24071386

Eloy Rodríguez-Deleón, José Báez + Show 2 more

Open Access

https://doi.org/10.3390/molecules24071386

Copy DOI

Abstract

Carotenoids are natural compounds that have important roles in promoting and maintaining human health. Synthetic astaxanthin is a highly requested product by the aquaculture industry, but natural astaxanthin is not. Various strategies have been developed to synthesize this carotenoid. Nonetheless, these approaches have not only provided limited global yields, but its main commercial source also carries several health risks for humans. In this contribution, the one-pot base-catalyzed reaction of (3R,3’R,6’R)-lutein (1) esters has resulted in a successful isomerization process to easily obtain up to 95% meso-zeaxanthin (2), which in turn is oxidized to (3R,3’S)-astaxanthin (3) with a global yield of 68%. The same oxidation performed with UV irradiation (365 nm) for 5 min provided the highest global yield (76%). These chemical transformations have also been achieved with a significant reduction of the health risks associated with its potential human consumption. Furthermore, this is the first time only one of the configurational isomers has been obtained semisynthetically. The poorly understood formation mechanisms of these two compounds were also investigated using Density-Functional Theory (DFT) calculations. These theoretical studies revealed that the isomerization involves a base-catalyzed deprotonation at C-6’, followed by C-4’ protonation, while the oxidation occurs via free radical mechanisms.

Highlights

Carotenoids are natural compounds synthesized by plants and some other photosynthetic organisms such as algae, some types of bacteria, and a small number of aquatic organisms, whereby they have diverse and crucial functions [1]
Carotenoids and some some apocarotenoids, which are sub-products resulting from the oxidative cleavage of a natural apocarotenoids, which are sub-products resulting from the oxidative cleavage of a natural carotenoid, have important inindustry industryasasnutraceutical nutraceutical additives, vitamin carotenoid, have importantcommercial commercial applications applications in additives, vitamin supplements, and cosmetic ingredients, supplements, and cosmetic ingredients,and andsome somehave haveapplications applicationsin inthe thepharmaceutical pharmaceutical industry industry [4]
The partial synthesis of zeaxanthin and use of high-pressure and transition metals for obtaining (3R,3’S)-astaxanthin (3) through a radical astaxanthin have been described in different patents, to date there has not been any report on the process

Summary

Introduction

Carotenoids are natural compounds synthesized by plants and some other photosynthetic organisms such as algae, some types of bacteria, and a small number of aquatic organisms, whereby they have diverse and crucial functions [1]. The partial synthesis of zeaxanthin and use of high-pressure and transition metals for obtaining (3R,3’S)-astaxanthin (3) through a radical astaxanthin have been described in different patents, to date there has not been any report on the process. The partial synthesis of zeaxanthin and astaxanthin have been described in different overall yield of this compound starting from lutein or lutein esters This opens an alternative way of patents, to date not beenproduct any report overall yield of this compound starting from obtaining this there highlyhas demanded and on thethe possibility of investigating its pharmacological lutein or lutein. This opens an in alternative obtaining this highly astaxanthin demanded product benefits as anesters.

Discussion

Method

Synthesis and Formation Mechanism of Astaxanthin from Zeaxanthin

Procedures

Computational Calculations

Conclusions