Reactive oxygen species (ROS) are continuously generated as a by-product of normal aerobic metabolism. Elevated ROS formation leads to potential damage of biological structures and is implicated in various diseases. Astaxanthin, a xanthophyll carotenoid, is a secondary metabolite responsible for the red-orange color of a number of marine animals and microorganisms. There is mounting evidence that astaxanthin has powerful antioxidant, anti-inflammatory, and antiapoptotic activities. Hence, its consumption can result in various health benefits, with potential for therapeutic application. Astaxanthin contains both a hydroxyl and a keto group, and this unique structure plays important roles in neutralizing ROS. The molecule quenches harmful singlet oxygen, scavenges peroxyl and hydroxyl radicals and converts them into more stable compounds, prevents the formation of free radicals, and inhibits the autoxidation chain reaction. It also acts as a metal chelator and converts metal prooxidants into harmless molecules. However, like many other carotenoids, astaxanthin is affected by the environmental conditions, e.g., pH, heat, or exposure to light. It is hence susceptible to structural modification, i.e., via isomerization, aggregation, or esterification, which alters its physiochemical properties. Here, we provide a concise overview of the distribution of astaxanthin in tissues, and astaxanthin structures, and their role in tackling singlet oxygen and free radicals. We highlight the effect of structural modification of astaxanthin molecules on the bioavailability and biological activity. These studies suggested that astaxanthin would be a promising dietary supplement for health applications.

Red pigmented marine bacteria, Pseudoalteromonas rubra strains PS1 and SB14, were isolated from two sampling locations in different ecosystems on Alor Island, Indonesia, and cultured in the laboratory. We analyzed the 16S rRNA gene sequences and examined the pigment composition and found that both strains produced cycloprodigiosin (3), prodigiosin (4), and 2-methyl-3-hexyl-prodiginine (5) as major compounds. In addition, we detected three minor compounds: prodigiosin derivatives 2-methyl-3-propyl prodiginine (1), 2-methyl-3-butyl prodiginine (2), and 2-methyl-3-heptyl-prodiginine (6). To our knowledge, this is the first report that P. rubra synthesizes not only prodigiosin and cycloprodigiosin but also four prodigiosin derivatives that differ in the length of the alkyl chain. The antimicrobial activity of cycloprodigiosin, prodigiosin, and 2-methyl-3-hexyl-prodiginine was examined by a disk-diffusion test against Escherichia coli, Staphylococcus aureus, Salmonella typhi, and Candida albicans. We found that, at a concentration of 20 μg/mL, cycloprodigiosin showed the greatest inhibition (25.1 ± 0.55 mm) against S. aureus.

Erythrobacter flavus strain KJ5 (formerly called Erythrobacter sp. strain KJ5) is a yellowish marine bacterium that was isolated from a hard coral Acropora nasuta in the Karimunjawa Islands, Indonesia. The complete genome sequence of the bacterium has been reported recently. In this study, we examined the carotenoid composition of this bacterium using high-performance liquid chromatography coupled with ESI-MS/MS. We found that the bacterium produced sulfur-containing carotenoids, i.e., caloxanthin sulfate and nostoxanthin sulfate, as the most abundant carotenoids. A new carotenoid zeaxanthin sulfate was detected based on its ESI-MS/MS spectrum. The unique presence of sulfated carotenoids found among the currently known species of the Erythrobacter genus were discussed.

No abstract

Erythrobacter flavus strain KJ5 (formerly called Erythrobacter sp. strain KJ5) is a yellowish marine bacterium that was isolated from a hard coral in the Karimunjawa Islands of Indonesia.