# Heterologous Production of 2,2′-Dihydroxy Derivatives of Astaxanthin and Adonirubin in Escherichia coli and Evaluation of Their Antioxidant Activity

## TL;DR

Scientists produced water-soluble versions of astaxanthin in E. coli and tested their antioxidant power.

## Contribution

A novel method for producing 2,2′-dihydroxy derivatives of astaxanthin and adonirubin in E. coli is presented.

## Key findings

- 2,2′-dihydroxyastaxanthin and 2,2′-dihydoxyadonirubin were successfully produced as dominant carotenoids in E. coli.
- The antioxidant activity of the derivatives was comparable to that of natural astaxanthin.

## Abstract

Astaxanthin is a prominent carotenoid with strong antioxidant activity due to its 13 conjugated double bonds and its 3,3′-hydroxy groups adjacent to its 4,4′-carbonyl groups. This red pigment is utilized as a food additive and nutritional supplement, and it also has applications in cosmetics. But the extremely low water solubility of astaxanthin limits its broader commercial application. In order to decrease the hydrophobic property of astaxanthin, we produced 2,2′-dihydroxy derivatives of astaxanthin and its intermediate adonirubin, (2R,3S,2′R,3′S)-2,2′-dihydroxyastaxanthin (1) and (2R,3S,2′R)-2,2′-dihydoxyadonirubin (2), in the cells of Escherichia coli as dominant carotenoids. This result was achieved by using the crtG gene that codes for zeaxanthin/canthaxanthin/astaxanthin 2,2′-hydroxylase, derived from Brevundimonas sp. strain SD212, in addition to astaxanthin biosynthesis genes that carry the Haematococcus pluvialis IDI, Pantoea ananatis crtE, crtB, crtI, crtY, crtZ, and Paracoccus sp. N81106 crtW genes. The singlet oxygen-quenching activities of 1 and 2 (IC50 4.3 μM and 8.3 μM, respectively) were examined and found to be comparable to that of astaxanthin (IC50 1.7 μM).