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Five polyketides, paralactonic acids A-E (1-5) were isolated from Paraconiothyrium sp. SW-B-1, an endophytic fungus isolated from the seaweed, Chondrus ocellatus Holmes. Their structures were determined by various spectroscopic methods, predominantly by 2D NMR spectroscopic analyses. The absolute configurations of compounds 1-5 were determined by comparison of the experimental and calculated ECD spectra. Compound 5 showed moderate antibacterial activity and restored the growth of a mutant yeast strain inhibited by hyperactivated Ca2+-signaling.

We evaluated the effects of red and blue light on the repair of UV-B radiation-induced damage in tetraspores of Chondrus ocellatus Holm. Tetraspores of C. ocellatus were treated with different UV-B radiation levels (0, 36, 72, 108, 144 and 180 J/m2), and thereafter subjected to PAR, darkness, or red or blue light during a 2-h repair stage, each day for 48 days. The diameters and cellular contents of cyclobutane pyrimidine dimmers (CPDs), chlorophyll a (Chl a), phycoerythrin, and UV-B-absorbing mycosporinelike amino acids (MAAs) contents of the tetraspores were determined. Our results show that low doses of UV-B radiation (36 and 72 J/m2) promoted the growth of C. ocellatus; however, increased UV-B radiation gradually reduced the C. ocellatus growth (greater than 72 J/m2). The MAAs (palythine and asterina-330) in C. ocellatus were detected and analyzed by LC/MS. Our results suggest that moderate red light could induce the growth of this alga in aquaculture. In addition, photorepair was inhibited by red light, so there may be some other DNA repair mechanism activated by red light. Blue light promoted the activity of DNA photolyase, greatly improving remediation efficiency. Red and blue lights were found to reduce the capacity of C. ocellatus to form MAAs. Therefore, PAR, red light, and blue light play different roles during the repair processes for damage induced by UV-B radiation.

Effects of enhanced ultraviolet B (UV-B, 280-320 nm) on macroalgae have gained particular attention in recent years. We investigated the changes in the growth, physiological and biochemical characteristics of C. ocellatus under UV-B radiation in this study. The results showed that UV-B could inhibit the growth of C. ocellatus (pC. ocellatus were not obvious. The soluble proteins content and MDA content in C. ocellatus were increased by UV-B radiation, and the increase of MDA content was extraordinary significant. The SOD activity and CAT activity were increased when the intensity of UV-B radiation was 7.2 J/m2, while the SOD activity and CAT activity were decreased when the intensity of UV-B radiation was 21.6 J/m2.

The EtOH extracts of red seaweeds (Symphyocladia latiuscula, Chondrus ocellatus and Carpopeltis affinis) and solvent partitioned fractions were investigated for their 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 1,1-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging effects and the total phenolic contents were correlated with ABTS and DPPH radical scavenging activities. The EtOH extracts and their solvent partitioned fractions exhibited strong ABTS and DPPH radical scavenging activities. Among the solvent partitioned fractions obtained from n-Hexane (HX), methylenchloride (MC), ethylacetate (EA), and buthanol (BuOH), the HX fraction from C. affinis showed higher radical scavenging activities than other fractions. Total phenolic contents showed significant correlation (r² = 0.709) with ABTS radical scavenging activity. The results of this study suggest that the strong radical scavenging activity of HX fraction from C. affinis is a promising natural antioxidant for healthcare products.

The effects of exposure to UV-B radiation, 280–315 nm, and dark or dark repair conditions on the early development of Chondrus ocellatus Holm collected from Qingdao coast were studied under the laboratory condition. After being exposed to different doses [0, 36, 72, 108, 144 and 180 J/(m2·d)] of UV-B radiation, one treatment of tetraspores were put back to normal culture condition (PAR), the other treatment were put into dark condition to repair for 2 h. During the cultivation, the diameter of the tetraspores were recorded every 4 d till the 50th day when vertical branches formed in all treatments. Then at the 50th day, CPDs, phycoerythrin, chlorophyll a and MAAs (Palythine and asterina-330) were measured. The results showed that low doses UV-B radiation could significantly accelerate the growth rate of the tetraspores of C. ocellatus and the growth rate reduced gradually with UV-B radiation keep on increasing. The variation trend of both the phycoerythrin and chlorophyll a concentration reduced significantly (P < 0.05) once given the UVB radiation. Under UV-B stress, the CPDs were induced, and the concentrations of CPDs were significant low in dark repair groups. The data of MAAs analyzed by LC/MS in the tetraspores of C. ocellatus suggested that there were two MAAs formed (palythine and asterina-330) after UV-B radiation induced, and low dose of UV-B irradiation could significantly induced the concentration of MAAs. From the growth and development state of the tetraspores, negative effects of UV-B radiation on the dark repair groups were more serious than PAR.

1. The mucilage of Chondrus ocellatus Holmes has been investigated by the partial methanolysis method. 2. A new disaccharide, the structure of which is shown to be 4-O-β-D-galactopyranosyl-3,6-anhydro-D-galactose, has been isolated in the form of its dimethylacetal and methyl β-glycoside in a good yield. 3. The disaccharide has been named carrabiose. 4. It has been suggested that 1→3′ linked carrabiose represents the repeating unit for the most part of the carbohydrate of the Chondrus mucilage.