**Kazutoshi Shindo 1,\* and Norihiko Misawa 2**

1 Department of Food and Nutrition, Japan Women's University, 2-8-1 Mejirodai, Bunkyo-ku, 

Tokyo 112-8681, Japan 

2 Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, 

1-308 Suematsu, Nonoichi-shi, Ishikawa 921-8836, Japan; E-Mail: nmisawa@ishikawa-pu.ac.jp 

**\*** Author to whom correspondence should be addressed; E-Mail: kshindo@fc.jwu.ac.jp; Tel./Fax: +81-35-981-3433.

*Received: 10 February 2014; in revised form: 3 March 2014 / Accepted: 4 March 2014 / Published: 19 March 2014* 

**Abstract:** Marine bacteria have not been examined as extensively as land bacteria. We screened carotenoids from orange or red pigmentsproducing marine bacteria belonging to rare or novel species. The new acyclic carotenoids with a C30 aglycone, diapolycopenedioc acid xylosylesters A–C and methyl 5-glucosyl-5,6-dihydro-apo-4,4<sup>ȝ</sup>lycopenoate, were isolated from the novel Gram-negative bacterium *Rubritalea squalenifaciens*, which belongs to phylum Verrucomicrobia, as well as the low-GC Gram-positive bacterium *Planococcus maritimus* strain iso-3 belonging to the class Bacilli, phylum Firmicutes, respectively. The rare monocyclic C40 carotenoids, (3*R*)-saproxanthin and (3*<sup>R</sup>*,2<sup>ȝ</sup>*S*)-myxol, were isolated from novel species of Gram-negative bacteria belonging to the family Flavobacteriaceae, phylum Bacteroidetes*.* In this review, we report the structures and antioxidant activities of these carotenoids, and consider relationships between bacterial phyla and carotenoid structures. 

**Keywords:** diapolycopenedioc acid xylosylesters A–C; methyl 5- glucosyl-5,6-dihydro-apo-4,4ȝ-lycopenoate; (3*R*)-saproxanthin; (3*<sup>R</sup>*,2<sup>ȝ</sup>*S*)- myxol; antioxidant activity 

## **1. Introduction**

Some species of bacteria, yeast, and fungi, as well as algae and higher plants, synthesize a large number of carotenoids with different molecular structures, and more than 750 carotenoids with different structures have been isolated from natural sources [1]. Many beneficial pharmaceutical effects of carotenoids have recently been reported*.* Therefore, evaluating the pharmaceutical potentials of various carotenoids may represent an interesting field in medical research. However, the number of carotenoid species that have been examined for this purpose has been limited, and has included C40 carotenoids possessing skeletons composed of 40 carbon atoms, such as dicyclic carotenoids, e.g., Ά-carotene, ΅-carotene, Άcryptoxanthin, zeaxanthin, lutein, canthaxanthin, astaxanthin, and fucoxanthin, and the acyclic carotenoid lycopene [2–8]. Difficulties have been associated with identifying natural sources to supply sufficient amounts of new or rare carotenoids, with the exception of carotenoids that can be isolated from a species of higher plants or algae or chemically synthesized. It has therefore been desirable to find cultivable bacteria that produce new or rare carotenoids, since they can easily be reproduced. 

Marine bacteria have not been examined as extensively as land bacteria. Thus, the Marine Biotechnology Institute Co., Ltd. (MBI, Kamaishi, Japan) was established in December, 1988, and continued to isolate novel or rare marine bacteria until March, 2008, the number of which reached more than ten thousand [9–12]. Many bacteria have been shown to produce dicyclic or monocyclic 

C40 carotenoids, in addition to some acyclic C30 carotenoids with a 30 carbon skeleton [1,13]. The 

MBI isolated new or rare dicyclic C40 carotenoids with the Ά-carotene ( Ά,Ά-carotene) skeleton 

from Gram-negative marine bacteria belonging to the class ΅-Proteobacteria, phylum 

Proteobacteria, e.g., astaxanthin glucoside from *Paracoccus* sp. strain N81106 (reclassified from 

*Agrobacterium aurantiacum*) [14], 2-hydroxyastaxanthin from *Brevundimonas* sp. strain SD212 [15], and 4-ketonostoxanthin 3ȝ-sulfate from *Erythrobacter* sp. strain. PC6 (reclassified from *Flavobacterium* sp. PC-6; MBIC02351) [16]. These marine bacteria were also able to produce astaxanthin [17]. The carotenoid biosynthesis gene clusters of these marine bacteria have been elucidated in detail [17–19]. 

The generation of free radicals has been suggested to play a major role in the progression of a wide range of pathological disturbances, including myocardial and cerebral ischemia [20], atherosclerosis [21], renal failure [22], inflammation [23], and rheumatoid arthritis [24]. The subsequent peroxidative disintegration of cells and organelle membranes has also been implicated in various pathological processes [25]. Carotenoid pigments, which have been shown to possess strong antioxidant activities, have been attracting increasing attention due to their beneficial effects on  human health, e.g., their potential to prevent diseases such as cancer and cardiovascular diseases [26]. 

We have attempted to identify novel or rare types of carotenoids from yellow or red 

pigment-producing marine bacteria that were classified to belong to rare or novel species by 16S rRNA analyses since 2002. The results of this screening led to the isolation of diapolycopenedioc 

acids xylosylesters A–C (new carotenoids) from *Rubritalea squalenifaciens* [27,28], methyl 

5-glucosyl-5,6-dihydro-apo-4,4ȝ-lycopenoate (a new carotenoid) from *Planococcus maritimus* [29], and 

(3*R*)-saproxanthin and (3*<sup>R</sup>*,2<sup>ȝ</sup>*S*)-myxol (rare carotenoids) from a novel species belonging to the family 

Flavobacteriaceae [30]. In this review, we report the structures and antioxidant activities of these carotenoids, and consider relationships between bacterial phyla and carotenoid structures. 
