Secondary Metabolites From Two Microorganisms Associated With Sea Cucumbers And Two Marine Invertebrates From The South China Sea

The China Sea is rich in biological resource. Marine invertebrates and microorganismscan possess structurally unique secondary metabolites with various bioactivities. This alreadybecome a hot research area for marine bioactive compounds.In order to discover biologically active substances from marine sources, This studyinvestigated the secondary metabolites of actinomycete Brevibacterium sp. associated with thesea cucumber Apostichopus japonicus Selenka, the fungus Engyodontium album associatedwith the South China Sea cucumber Holothuria nobilis Selenka, a soft coral Sinularia sp., anda sponge Theonella swinhoei.47compounds were isolated by means of repeated columnchromatography on silica gel, Sephadex LH-20, and high performance liquid chromatography(HPLC). On the basis of detailed spectroscopic analysis (nuclear magnetic resonance, NMR;mass spectrometry, MS) in combination of comparison with reported data, their structureswere elucidated as: cyclo-(L-Pro-L-Phe), cyclo-(L-Pro-L-Leu), cyclo-(L-Pro-L-Tyr), cyclo-(L-Pro-L-Val), cyclo-(L-Pro-L-Val), cyclo-(L-Ale-L-Leu), cyclo-(L-Leu-L-Tyr), cyclo-(L-Pro-L-Pro), cyclo-(L-Ale-L-Ile), cyclo-(L-Thr-L-Leu), cyclo-(L-Pro-L-Phe), indole formic acid,indoleformic acid, indoleacetic acid, indolalcohol, indoleacetic acid methyl ester,(22E,24R)-5,8-epidioxy-ergosta-6,22-dien-3-ol,(22E,24R)-ergosta-5,7,22-trien-3-ol,(22E,24R)-ergosta-7,22-dien-3,5,6-triol,3,5-dihydroxy-(22E,24R)-ergosta-7,22-dien-6-one,3,5-dihydroxy-6-methoxy-ergosta-7,22-diene, Sinularin, dihydrosinularin, flexilarin B,5-dehydrosinularolide, sinulaflexiolide A,3,4:8,11-bisepoxy-7-acetoxycembra-15(17)-en-1,12-olide,11-epi-sinulariolide acetate, sinulariolide, ergosta-5,24(28)-dien-3,7,11,16-tetrol,ergosta-5,24(28)-dien-3-ol, ergosta-5,22,24(28)-trien-3-ol, and cholesterol,(2Z,6R,8S)-3,6-epoxy-4,6,8-triethyl-2,4-dodecadienoate,(2Z,6R,8R,9E)-3,6-epoxy-4,6,8-triethyl-2,4,9-dodecatrienoate,(2Z,6R,8R,9E)-2-Bromine-3,6-epoxy-4,6,8-triethyl-2,4,9-dodecatrienoate,thymidine.Secondary metabolites from two marine microorganisms one coral and one sponge wereinvestigated.47compounds were isolated by means of detailed spectroscopic analysis, with4new compounds GE-9, LG-1, LG-2, LG-9. Some of the isolated compounds showed differentbioactivity. Compounds HS-1, HS-2, and HS-3showed different inhibition against Vibrioanguillarum. Compound GJ-1showed anti-fungul activity. Compound GJ-4showed cytotoxicity against A549cell lines. This study enriched the number of natural products frommarine, and it was significant for the development of our marine resources.In the course of searching for biologically active substances, we try to explore therelationship between microorganism and their hosts. The compounds isolated frommicroorganism are structurally far from the known biologically active saponins. We can saythat the two microorganism are not involved in their hosts’ metabolism. What may the twomicroorganism do in defence of sea cucumbers’ enemy still need further study.We get one tetraterpenoid from soft coral Sinularia sp.. The compound GE-8is veryhelpful to further investigate the tetraterpenoids of soft coral Sinularia sp.. And, we get twonew4-methyel sterols and one easter from the sponge Theonella swinhoei. This easter belongto a class of marine ligands of peroxisome proliferator-active receptor. We.hypothesis this classof compounds are generated by microorganisms associated with sponge and coral, which needfurther study.