Studies On The Chemical Constituents And Bioactivities Of Three Marine Organisms

In our ongoing program to search for natural products with unique structural features and pronounced biological activities from marine organisms, the soft coral Nephthea sp., marine sponge Pseudoceratina sp. and an undescribed marine sponge were collected from Hainan Island, South China Sea. An extensive chromatographic examination was resulted in the isolation of 71 compounds from the selected marine soft coral and sponges, of which ten were identified as new compounds and one was isolated from nature for the first time. Their structures were determined on the basis of MS, NMR, CD, Mosher method and by comparison with the reported data in literature. Most of the compounds were tested for antitumor, inhibitory effect on proteasome ChT-L, brine shrimp lethality and antimicrobial activities.Among the isolated compounds, 24 were isolated and identified from the soft coral Nephthea sp., including five new compounds, namely 4α-methyl-ergost-7, 24 (28)-diene-3β-ol-23-one (1), 4α-methyl-ergost-8 (14), 24 (28)-diene-3β-ol-23-one (2),4α-methyl-ergost-24 (28)-en-3β, 11β-diol-23-one (3), Ergost-5, 24 (28)-diene-3β, 23S-diol (4) and Ergost-5, 25-diene-3β, 24S, 28-triol (6). The structure patterns were classified as steroids (1~14), sesquiterpenes (15), amino acid derivatives (16), benzene derivatives (17~18), lipids (19~22) and nucleotides (23~24). Compounds 7 and 9 showed weak cytotoxic activities against HL-60 human leukemic cell and A-549 human lung cancer cell, while compounds 8 showed moderate cytotoxic activities against HL-60 human leukemic cell and A-549 human lung cancer cell.From the marine sponge Pseudoceratina sp., 22 compounds were isolated and characterized, involved two new compounds, namely purealidins T (25) and purealidins U (26), while compound 31 was originated from synthesized product, but was found as a natural product for the first time. The structure types included bromotyrosine alkaloids (25~35), amino acid derivatives (36), lipids (37, 43), chlorophyll derivatives (38), steroids (39~42), benzene derivatives (44) and nucleotides (45~46). The N-oxide containing compound purealidins T (25) was rarely occurred in marine organisms, this is the second report on N-oxide containing bromotyrosine alkaloid. The abundant purealidin Q (27) could be assumed as a chemotaxonomic marker. Purealidins U (26) exhibited antimicrobial activity against Staphylococcus aureus ATCC 25923 (inhibitory rate 85.6% under 100μg/ml). In addition, 25 compounds were isolated and identified from an undescribed sponge, among them, compounds (20Z) 8, 13-diol-variabilin (47), 48 and 58 were identified as new compounds. The structure patterns involved sesterterpenoids (47~57), monoterpenoid derivatives (58~59), steroids (60~61), indole derivatives (62~65), benzene derivatives (66~69) and nucleotides (70~71). The acetal-containing sesterterpenoids 50 and 51 exhibited significant activity against brine shrimp.