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To date,only 5%of the total numbers of fungal species have been described in nature.In marine and some other extreme environments,the difficulty of sampling even hindered the exploitation of these microbial resources.Microorganisms from extreme living conditions often have unique metabolic pathways which are different from ordinary terrestrial microbes,sometimes leading to the production of novel secondary metabolites with unique bioactivities,provides new opportunities for natural products and drug development research.Based on our groups early study on 20 fungal strains from deep marinesediment,collected from South China Sea,W-20,which showed a certain anti-Aβ peptide aggregation activity,was chosen for further study.W-20 was then identified as Aspergillus sp.based on ITS rDNA sequencing analysis.6 compounds were isolated from the fermentation broth of Aspergillus sp.SCSIOW20,by using normal and reverse phase silica gel,Sephadex LH-20,and HPLC.The structures were identified by spectroscopic analysis as diorcinol(1),sydowic acid(2),monodictyphenone(3),ergosterol(4),syodonic acid(5)and C15/C15-epi-WIN 64821(6).All compounds were tested for anti-A peptide aggregation activities,compound 6 exhibited comparable activity(relative inhibitory rate: 42.9 ± 5.9%)with positive control,EGCG.This is the first report for diketopiperazines type compounds showing anti-Aβ peptide aggregation activity.To increase the diversity of secondary metabolites,suberic bishydroxamate(SBHA),one of the histone deacetylase inhibitors,was used to induce W-20 secondary metabolites production.As a result,another metabolite: sydonol(7)was obtained.