The Secondary Metabolites And Their Bioactivities Of A Gorgonian And Two Gorgonian Derived Fungi

Corals are one of the common marine invertebrates in tropical coral reefecosystem. The surfaces of them are smooth without other substances attached, andthey are able to survive in the harsh marine environment. We deduce that they maydepend on the chemical defensive substances probably produced by themselves andtheir symbiotic microorganisms. These substances with the chemical ecologicalactivities usually have good pharmacological activities. Based on that, in presentstudy, the secondary metabolites from a gorgonian and two gorgonian-derived fungifrom the South China Sea were isolated and identified under the guidance of bioassayand the biological activities of the isolated compounds were evaluated, in order todiscover compounds of novel structures and good bioactivities.Investigation on the gorgonian Anthogorgia ochracea (GX BH WZ07) led tothe isolation of six guaiazulene-based analogues, among which1and2are newcompounds. The planar structures of the new compounds were elucidated bycomprehensive spectroscopic data. The absolute configuration of1was determined as3R by the comparison of TDDFT calculated electronic circular dichroism with itsexperimental spectrum. Compound1is a rare guaiazulene-based analogue possessinga unique C16skeleton and the extra formyl carbon was formed by an intermolecularone-carbon-transfer reaction. The compounds were tested for the antiproliferativeeffects on zebrafish Danio rerio embryo, antifouling activity, cytotoxicity,antibacterial activity and antiviral activity. Compound3showed strongantiproliferative effects leading to abnormal several aspects of the embryonicdevelopment including coagulated eggs (48h), notochord malformation (72h), andembryo death (72h) with the EC50values of0.90,1.47and1.67μg/mL, respectively.Compounds3and4showed significant inhibition against the larval settlement ofbarnacle Balanus amphtrite with the EC50values of9.50and3.12μg/mL, respectivelyand the LC50values both higher than50μg/mL, which indicated that these twocompounds have high efficiency with low toxicity.Analysing comprehensively the follwing fators, including the shapes of the fungi,the TLC and HPLC of the EtOAc crude extracts and their antibacterical activities, of the17fungi separated from the above gorgonian, we selected Chaetomium globosum(RA073) as the study target. Twelve known compounds were obtained from thefungus, including two azaphilones (7–8), seven cytochalasans (9–15), one tetralonederivative (16), one isocoumarin derivative (17), and one macrocyclic o-phthalateester (18). The compounds were tested for biological assays and compounds10and15showed comprehensive antibacterial activities. Both compounds exhibited strongerinhibitory activities against Tetragenococcus halophilus, with the MIC values of0.21and0.37μg/mL, respectively. They also exhibited obvious Artemia salina lethalactivity with the LC50values of9.72and12.41μg/mL, respectively.Eight compounds were isolated from the Aspergillus sp.(XS20090B15) of thegorgonian Muricella abnormalis collected from the south China sea, which containedfive cytochalasans (19–23), one heterocyclic compound (24), and two steroids (25–26). The compounds were evaluated for biological assays. Compounds19,20,22and26showed inhibitory activities against T. halophilus, with the MIC values of3.13,3.13,6.24and6.23μg/mL, respectively.21exhibited obvious Artemia salina lethalactivity with the LC50values of12.40μg/mL.In present study,26compounds were obtained from the secondary metabolitesfrom a gorgonian and two gorgonian-derived fungi, mainly including terpenes andcytochalasans, and there were two new compounds. Part of the guaiazulene-basedanalogues showed antiproliferative effects on zebrafish embryo and inhibition againstthe larval settlement of barnacle B. amphtrite and part of the cytochalasans exhibitedantimicrobial activities and were toxic to brine shrimp (A. salina), which supply thebasis of compounds for the study on the chemical ecological relationship between themarine invertebrates and their symbiotic microorganisms.