---

Marine microorganisms are important sources for novel natural products. Hence, the aim of this study was to introduce marine microorganisms with the capability of producing antioxidant and cytotoxic metabolites. For this purpose, ten live sea cucumbers (Holothuria leucospilota) were collected from Larak Island, Persian Gulf. Then, their intestine contents were serially diluted and treated by heating (55°C). 100 µL of treated samples were inoculated on starch casein nitrate agar medium, which is supplemented with nalidixic acid and cycloheximide. The plates were incubated at 28 °C for 4 weeks and the colonies were purified. The antioxidant activity of extracted metabolites from the isolated actinobacteria was evaluated using DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity assay and the cytotoxic activity was screened by Brine-Shrimp micro well cytotoxicity method. In addition, the cytotoxic effect was evaluated against HCT 116 and SW 480 cell lines by MTT cell proliferation assay. A new strain of marine actinobacterium represented maximum antioxidant and cytotoxic activity among 17 actinobacterial isolates. The ethyl acetate culture extract of the isolate scavenged DPPH radicals with IC₅₀ value of 211.2 µg mL^-1. In addition, the extract exhibited high toxicity against HCT 116 and SW 480 tumor cell lines with IC₅₀ values of 26.48 and 18.53 µg mL^-1 respectively. The isolate was identified as Streptomyces sp. strain SC 156 and showed 98% similarity with type strains in NCBI database. These results suggested that Streptomyces sp. strain SC 156 could be considered as promising candidate for antioxidant and cytotoxic compound discovery. 

---

In search for bioactive products, three zoanthid species (Zoanthus spp., Palythoa tuberculosa and Palythoa mutuki) were collected from offshore zone of Hengam Island. Three extracts of each zoanthids (methanol, dichloromethane (DCM) and n-hexane) were tested for antifungal and antibacterial activities against certified strains of bacteria (two Gram-positive: Bacillus subtilis, Staphylococcus aureus and three Gram-negative: Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris) and fungi (Candida albicans, Microsporum gypseum, Microsporum canis) through the disk diffusion assay. Cytotoxic activity of these extracts was evaluated against Artemia nauplii. The results showed that 8 extracts (88.88%) of the zoanthids were active against at least one bacterial strain and 6 extracts (66.6%) were active against at least one fungus (the activity against bacteria was moderate). Also, minimum inhibitory concentrations (MICs) of the extracts with desirable (inhibition zone more than 9mm) in the previous stage were assessed. Among the 9 zoanthids extract, 88.88% showed activity against some of the five bacteria, and 66.6% showed activity against some of the three fungi. The most active zoanthid extract against three fungi was dichloromethane extract of the Zoanthus ssp. that showed promising antifungal activity against Candida albicans in vitro models. The minimum inhibitory concentrations and LC₅₀ values of dichloromethane extract of Zoanthus ssp were 125μg/mL and 181μg/mL, respectively. Therefore, this extract can be a candidate for candidiasis therapy.  LC₅₀ of DCM, crude extract of Palythoa mutuki was 31µg/ml, showing high toxicity. This is the first report of biological activities of marine zoanthids from an Iranian Island of Persian Gulf.

---

The resistance of cancerous cells to anti-cancer drugs is one of the most common problems in medicine and therefore, finding new anti-cancer compounds with the least side effects seems to be necessary. The present study was performed to investigate the anti-cancer potential of Padina gymnospora and Acanthophora spicifera, two native algae species of the Persian Gulf, in vitro. In this regard, methanol, chloroform, n-hexane, and ethyl acetate extracts of both algae species were added to cultivated MCF-7 cells at different concentrations (125, 250, 500, and 1000 μg/mL). 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay was used to determine the toxicity effects of algae extracts on MCF-7 cells. DNA isolation and agarose gel electrophoresis were also performed to assess DNA fragmentation induced by these two algae species. Based on the MTT results, the sensitivity of cultivated MCF-7 cells to P. gymnospora and A. spicifera extracts was increased in a dose-dependent manner. The highest concentration of methanolic extract of both algae species significantly affected the MCF-7 cells and led to the highest cell death. Moreover, the IC50 of P. gymnospora and A. spicifera methanolic extracts for the MCF-7 cells were equal to 557.78 and 910.61 μg/ml, respectively, which indicates P. gymnospora has more cytotoxic activity and anti-tumor potency. The lowest concentration of all types of algae extracts was not considerably cytotoxic to cultivated MCF-7 cells. The DNA fragmentation of MCF-7 cells was increased with increasing the concentration of the algal extracts. The highest amount of DNA fragmentation caused by 1000 μg/mL of P. gymnospora and A. spicifera extract; however, methanolic extract of P. gymnospora caused more DNA fragmentation in MCF-7 cells than A. spicifera.

---

It is believed that the marine animals contain many compounds that could be beneficial for the treatment of many diseases. In this study, the acetone extract of Stichopus hermanni was fractionated by a liquid chromatography and then fractions were assayed for terpenoids. The fraction C18 that received a positive response for terpenoids was purified further and characterized by the liquid chromatography, mass spectral, and Thin-layer chromatography analysis. A terpenoid compound, squalene, was identified as the constituent of the bioactive extract fraction. Antimicrobial activity of C18-3 was tested against Bacillus subtilis, Bacillus cereus, Pseudomonas aeruginosa, Salmonella typhi, Proteus vulgaris, Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, and Nocardia brasiliensis pathogens. The lowest MIC and MBC values were observed in the Bacillus cereus (50 µg/mL) and Staphylococcus aureus (500 µg/mL), MIC and MFC the fungal pathogen Candida albicans (400 and 2000 μg/mL) and was cytotoxic against KB/ C152 and HUT-78/C185 cells (IC50 6.1 μg/mL and 6.29 μg/mL). This research suggests S. hermanni can be used as an alternative source for the separation and purification of squalene compound as a medicinal supplement. 

---

Screening of marine bacteria for developing new drugs is an emerging field in marine biotechnology. The purpose of this study was to investigate the diversity of sponge-associated bacteria from Kish and Larak islands (Persian Gulf) and to determine their antimicrobial, antioxidant, and cytotoxic activities. After sampling, bacteria were grown on the marine sponge agar medium. The isolated bacteria were characterized by polyphasic methods. The antimicrobial activity of the isolated bacteria was determined by the microdilution broth method. Cytotoxic activity was evaluated by MTT (3-4,5-dimethylthiazol-2yl-2,5-diphenyltetrazolium bromide) assay on human cell lines. Antioxidant activity was performed by inhibiting DPPH free radicals. Among 121 bacterial isolates, Vibrio and Bacillus genera were the dominant frequency. The minimum inhibitory concentration of the extracted metabolites was recorded in the range of 64 to 512 µg/mL. The IC₅₀ of antioxidant activity varied from 73.42 to 670.90 µg/mL. The cytotoxic activity of the extracted metabolites ranged from 40.57 to 181.80 µg/mL against SW 480 cell line and 141.30 to 359.70 µg/mL against HepG2 cell line. The HL 15, HL 85, and HK 5 extracts showed less toxicity against human umbilical vein endothelial cells. The results of genetic identification based on the comparison of 16S rRNA gene sequence showed that the potent strains HL 15, HL 24, HL 85, HK 5, and HK 36 belonged to B. safensis, V. alginolyticus, V. rotiferianus, B. aureus and Pseudomonas paralactis, respectively. The present study provided a new understanding of the diversity pattern and biological activity of the bacteria associated with Haliclona oculata.