A new sulfated triterpene glycoside from the sea cucumber Colochirus quadrangularis, and evaluation of its antifungal, antitumor and immunomodulatory activities.

Our continuing search for marine bioactive secondary metabolites led to the screening of crude extracts of sea cucumbers by the model of Pyricularia oryzae. A new sulfated triterpene glycoside, coloquadranoside A (1), together with four known triterpene glycosides, philinopside A, B, E and pentactaside B (2-5) were isolated from the sea cucumber Colochirus quadrangularis, and their structures were elucidated using extensive spectroscope analysis (ESI-MS, 1D and 2D NMR) and chemical methods. Coloquadranoside A possesses a 16-acetyloxy group in the holostane-type triterpene aglycone with a 7(8)-double bond, a double bond (25,26) at its side chain, and two ß-d-xylose in the carbohydrate chain. Coloquadranoside A exhibits in vitro some antifungus, considerable cytotoxicity (IC50 of 0.46-2.03 µM) against eight human tumor cell lines, in vivo antitumor, and immunomodulatory activity.

Cytotoxic holostane-type triterpene glycosides from the sea cucumber Pentacta quadrangularis.

Two new holostane-type triterpene glycosides, named pentactasides I (1) and II (2), and a new natural product, pentactaside III (3), together with two known glycosides, philinopsides A (4) and B (5), were isolated from the sea cucumber Pentacta quadrangularis. Their structures were elucidated by extensive spectroscopic analysis and chemical evidences. Compounds 1 and 2 possess the same trisaccharide moiety which is a rare structural feature among naturally occurring sea cucumber glycosides and has been infrequently reported, while 3 is a sulfated diglycoside. All the glycosides showed significant in vitro cytotoxicities against six tumor cell lines (P-388, A-549, MCF-7, MKN-28, HCT-116, and U87MG) with IC(50) in the range of 0.60-3.95 µM.

Iridoid glycosides from Saprosma ternatum.

Three new iridoid glycosides, epiasperuloside (1), epipaederosidic acid (2), and epipaederoside (3), together with 7 known compounds, were isolated from the 85% ethanol extract of the leaves of Saprosma ternatum Hook. f. Their structures were determined by application of spectroscopic (NMR, MS) and chemical methodologies. The antioxidant activity was evaluated for all isolates in terms of both DPPH and ABTS bioassays. Epiasperuloside (1) showed some antioxidant activity.

Two new cytotoxic disulfated holostane glycosides from the sea cucumber Pentacta quadrangularis.

Two new disulfated triterpene glycosides, pentactasides B and C (1 and 2, resp.), were isolated from the sea cucumber Pentacta quadrangularis collected from the South China Sea. Their structures were elucidated by extensive spectral analysis (2D-NMR and MS) and chemical methods. The compounds 1 and 2 possess the same tetrasaccharide moieties with two sulfated groups, but are different in the side chains of the triterpene aglycone. Pentactasides B and C (1 and 2, resp.) showed significant cytotoxicities (IC(50) 0.09-2.30 microM) against different human tumor cell lines.

Marine drugs--macrolactins.

The increasing demands for new lead compounds in pharmaceutical and agrochemical industries have driven scientists to search for new bioactive natural products. Marine microorganisms are rich sources of novel, bioactive secondary metabolites, and have attracted much attention of chemists, pharmacologists, and molecular biologists. This mini-review mainly focuses on macrolactins, a group of 24-membered lactone marine natural products, aiming at giving an overview on their sources, structures, biological activities, as well as their potential medical applications.

Isolation and structure of the cytotoxic cycloheptapeptide phakellistatin 13.

A new cyclic heptapeptide phakellistatin 13 (1) had been isolated from the sponge Phakellia fusca Thiele, collected at Yongxing Island of China. Its structure was elucidated as cyclo-(Pro1-Trp-Leu-Thr-Pro2-Gly-Phe) on the basis of MS, UV, IR, and high-field NMR (600 MHz) analysis. The compound was significantly cytotoxic against the human hepatoma BEL-7404 cell line with an ED(50) < 10(-2) microg/mL.

Bioactive steroids from the brown alga Sargassum carpophyllum.

By activity-guided fractionation, two new sterols, 3beta,28xi-dihydroxy-24-ethylcholesta-5,23Z-dien (1) and 2a-oxa-2-oxo-5alpha-hydroxy-3,4-dinor-24-ethylcholesta-24(28)-ene (2), together with five known steroids, fucosterol (3), 24-ethylcholesta-4,24(28)-dien-3,6-dione (4), 24xi-hydroperoxy-24-vinylcholesterol (5), 24-ketocholesterol (6), 24R,28R- and 24S, 28S-epoxy-24-ethylcholesterol (7), were isolated from the brown alga Sargassum carpophyllum as active compounds causing morphological abnormality of Pyricularia oryzae mycelia. Compounds 1, 3, 4, 5 and 7 also exhibited cytotoxic activity against various cancer cell lines. The IC50 values for 1 and 5 against HL-60 were 7.8 and 8.5 microg/ml, 3 and 4 against P-388 were 0.7 and 0.8 microg/ml, whereas 7 against MCF-7, HCT-8, 1A9, HOS and PC-3 were 4.0, 8.8, 10.0, 10.0 and 7.2 microg/ml, respectively.

[Studies on the chemical constituents from marine brown alga Ishige okamurai (3)].

OBJECTIVE: To study the chemical constituents of Ishige okamurai. METHOD: Compounds were isolated by Pyricularia oryzae bioassay-guided fractionation method in combination with extraction and partitionation as well as multi-chromatography. Their structures were determined by spectral analysis and chemical evidence. RESULT: Seven compounds were obtained and identified as (2S)-1-O-palmitoyl-2-O-(11Z-octadecenoyl)-3-O-beta-D-galacto-pyranosyl glycerol (I), (2S)-1-O-palmitoyl-2-O-myristoyl-3-O-(6-sulfo-alpha-D- quinovopyranosyl) glycerol (II), (2S)-1-O-palmitoyl-2-O-palmitoyl-3-O-(6'-sulfo-alpha-D- quinovopyranosyl) glycerol (III) and (2S)-1-O-palmitoyl-2-O-(11Z-octadecenoyl)-3-O-(6'-sulfo-alpha-D- quinovopyranosyl) glycerol (IV), stearic acid (V), methyl myristate(VI) and palmitic acid (VII). CONCLUSION: Compounds I-VI were isolated from the alga for the first time while I, II and IV are new natural products. I-IV showed activity causing morphological abnormality of P. oryzae mycelia.