Extract of Saccharina japonica induces apoptosis companied by cell cycle arrest and endoplasmic reticulum stress in SK-Hep1 human hepatocellular carcinoma cells.

Saccharina japonica is a family member of Phaeophyceae (brown macro-alga) and extensively cultivated in China, Japan and Korea. Here, the potential anti-cancer effect of n-hexane fraction of S. japonica was evaluated in SK-Hep1 human hepatocellular carcinoma cells. The N-hexane fraction reduced cell viability and increased the numbers of apoptotic cells in a both dose- and time-dependent manner. Apoptosis was activated by both caspase-dependent and independent pathways. The caspase-dependent cell death pathway is mediated by cell surface death receptors and activated caspase-8 amplified the apoptotic signal either through direct activation of downstream caspase-3 or pro-apoptotic proteins (Bad, Bax and Bak) subsequently leading to the release of cytochrome c. On the other hand, caspase-independent apoptosis appeared mediated by disruption of mitochondrial membrane potential and translocation of AIF to the nucleus where they induced chromatin condensation and/or large-scale DNA fragmentation. In addition, the n-hexane fraction induced endoplasmic reticulum (ER)-stress and cell cycle arrest. The results suggested that potential anti-cancer effects of n-hexane extract from S. japonica on SK-Hep1 cells.

The anticancer effects of Saccharina japonica on 267B1/K-ras human prostate cancer cells.

Saccharina japonica (S. japonica), a brown macro-alga, has been used as a traditional medicine in Korea for thousands of years. In this study, the potential anticancer effects of S. japonica were evaluated on 267B1/K-ras human prostate cancer cells. The exposure of cells to the extract induced inhibition of cell growth by increasing the number of apoptotic cells with cell shrinkage and inhibition of cell cycle progression. The effects of the extract on the cells were assessed by studying the cleavage of caspases and the target proteins of caspases. The increased expression of various cleaved caspases and changed expression of other proteins related in the apoptosis pathway were observed. 4'-6-Diamidino-2-phenylindole (DAPI) and immunofluorescence staining showed the cells undergoing apoptosis. Apoptosis induced changes in the expression of proteins involved in a variety of signaling pathways such as endocellular reticulum (ER) stress, death receptor and mammalian target of rapamycin (mTOR)-FoxO-mediated pathways. The data suggest that the extract (n-hexane sub-fraction) of S. japonica, induces apoptosis and cell cycle arrest in 267B1/K-ras human prostate cancer cells, and has potential as a complementary agent for cancer prevention.

Dyadobacter koreensis sp. nov., isolated from fresh water.

A non-motile, rod-shaped, light-yellow-pigmented bacterium, designated strain WPCB159(T), was isolated from freshwater samples collected from the Woopo wetland in Korea. The cells were Gram-negative, aerobic and catalase- and oxidase-positive. The major fatty acids were C(16 : 1)omega7c (34.8 %), iso-C(15 : 0) (24.2 %) and C(16 : 0) (9.4 %). The DNA G+C content was 44 mol%. A phylogenetic tree based on 16S rRNA gene sequences showed that strain WPCB159(T) forms a lineage within the genus Dyadobacter (family 'Flexibacteraceae') and is closely related to Dyadobacter hamtensis HHS 11(T) (97.8 % sequence similarity) and to other members of the genus Dyadobacter (95.2-96.8 % sequence similarity). The phenotypic characteristics and DNA-DNA hybridization relatedness data indicate that strain WPCB159(T) should be distinguished from D. hamtensis HHS 11(T). On the basis of the evidence presented in this study, strain WPCB159(T) represents a novel species of the genus Dyadobacter, for which the name Dyadobacter koreensis sp. nov. is proposed. The type strain is WPCB159(T) (=KCTC 12537(T)=NBRC 101116(T)).

Tyrosinase inhibitors isolated from the edible brown alga Ecklonia stolonifera.

Extracts from seventeen seaweeds were determined for tyrosinase inhibitory activity using mushroom tyrosinase with L-tyrosine as a substrate. Only one of them, Ecklonia stolonifera OKAMURA (Laminariaceae) belonging to brown algae, showed high tyrosinase inhibitory activity. Bioassay-guided fractionation of the active ethyl acetate (EtOAc) soluble fraction from the methanolic extract of E. stolonifera, led us to the isolation of phloroglucinol derivatives [phloroglucinol (1), eckstolonol (2), eckol (3), phlorofucofuroeckol A (4), and dieckol (5)]. Compounds 1 approximately 5 were found to inhibit the oxidation of L-tyrosine catalyzed by mushroom tyrosinase with IC50 values of 92.8, 126, 33.2, 177, and 2.16 microg/mL, respectively. It was compared with those of kojic acid and arbutin, well-known tyrosinase inhibitors, with IC50 values of 6.32 and 112 microg/ mL, respectively. The inhibitory kinetics analyzed from Lineweaver-Burk plots, showed compounds 1 and 2 to be competitive inhibitors with Ki of 2.3x10(-4) and 3.1x10(-4) M, and compounds 3 approximately 5 to be noncompetitive inhibitors with Ki of 1.9x10(-5), 1.4x10(-3) and 1.5x10(-5) M, respectively. This work showed that phloroglucinol derivatives, natural compounds found in brown algae, could be involved in the control of pigmentation in plants and other organisms through inhibition of tyrosinase activity using L-tyrosine as a substrate.