**2. Results**

*2.1. Diapolycopenedioc Acid Xylosylesters A–C from Rubritalea Squalenifaciens [27,28]* 

A yellow pigment-producing bacterium (strain HOact23T) that was found to produce squalene was isolated from the homogenate of the marine sponge *Halicondria okadai*, which had been collected 

from the Miura peninsula (Kanagawa, Japan), and was subsequently classified as a novel species in the genus *Rubritalea*, belonging to phylum Verrucomicrobia, based on 16S rRNA gene sequence data. The name proposed for the new taxon was *Rubritalea squalenifaciens* [31], with the type strain 

HOact23T (=MBIC08254T = DSM 18772T). 

*R. squalenifaciens* was cultured in 100 mL of medium (1.0% starch, 0.4% yeast extract, and 

0.2% peptone in seawater) in a 500 mL Erlenmeyer flask at 30 °C on a rotary shaker at 120 rpm for 2 days, and the carotenoids produced were purified from the cells using chromatographic methods (EtOAc/H2O partition ė silica gel column chromatography CH2Cl2–MeOH (20:1) ė preparative silica gel HPLC CH2Cl2– MeOH (15:1) ė preparative ODS HPLC (MeOH)). Three carotenoids were purified from cells in the 42-liter culture (diapolycopenedioc acids xylosylesters A (**1**) 10.2 mg, B (**2**) 3.0 mg, and C (**3**) 2.2 mg, respectively). The structures of compounds **<sup>1</sup>**–**<sup>3</sup>** were determined by HRESI-MS and spectroscopic (UV-Vis, NMR (1D and 2D investigations on 1H and 13C nuclei), and [΅]D) analyses as shown in Figure 1. Compounds **<sup>1</sup>**–**3** were all new carotenoids. 

Compounds **<sup>1</sup>**–**3** possessed diapolycopenedioc acid (C30 carotenoid) [32,33] as their aglycone. Diapolycopenedioic acid glucosyl ester and diapolycopenedioic acid diglucosyl were previously shown to be carotenoids that possessed diapolycopenedioc acid as the aglycone [32]. Compounds **<sup>1</sup>**–**3** were the first carotenoids to include 2-acyl-D-xylose in their structures. 

The antioxidant activity of compound **1** was evaluated using 1O2 suppression activity. Its IC50 was 5.1 ΐM (the IC50 values of astaxanthin and Ά-carotene were 8.9 ΐM and >100 ΐM, respectively). 
