Study On Secondary Metabolites And Biological Activities From Two Streptomyces Sp.

Microbial secondary metabolites have been discovered as antibiotics and have been shipped to the pharmaceutical industry for quite some time.Streptomyces,especially isolated from soil,is the main source of most antibiotics.Fifty years ago,with the discovery of sulfonamides,penicillins and streptomycin,the golden age of antibiotics began,followed by the successful characterization of tetracycline,macrolides,glycopeptides,cephalosporins and nalidixic acids;In the past 20 years,no less than 50 antibiotics have been developed.Large pharmaceutical companies are also meeting the needs of modern healthcare by improving the original drugs from generation to generation.However,the number of new antibiotics discovered has been decreasing over the past 20 years.As antibiotics continue to be resisted in clinical applications,the demand for new antibiotics will not decrease.When a new antibiotic is delivered to the clinic,it is effective at first.However,in order to survive,the pathogen will produce various mutations to adapt to the antagonism of this antibiotic.Eventually,a small number of bacteria will acquire a drug resistance mechanism.Antibiotics fail.Therefore,we continue to need new antibiotics to join.In this study,we collected two samples,namely the high salt concentration sample of Qinghai Salt Lake and the soil sample of Hainan,as the research object.Three different culture media were used for the salt lake samples,and 8 strains of strains were selected from the moderate salt concentration gradient.The antibacterial activity was screened and found to be one of the fungi against Beauveria bassiana,Metarhizium anisopliae and Verticillium marcescens.Good inhibition effect;For soil samples,three different culture mediums,such as Gaoshi No.1 medium,sporulation medium and S medium,were used,and 42 strains were obtained from the soil samples,and the bacteria were screened by the sputum method.Eleven strains have different degrees of antagonism to the indicator fungi,and seven of the 11 strains indicate different degrees of inhibition of the bacteria.The strain OC1610-4 was provided by the laboratory.The S medium was selected.After liquid fermentation,the crude extract was separated and purified by normal phase column chromatography and reverse phase column chromatography.A compound saquayamycin B was identified by nuclear magnetic resonance.The antibacterial activity of saquayamycin B was evaluated by paper sheet.It is concluded that it has no inhibitory effect on the selected indicator fungi,and has no inhibitory effect on Gram-negative bacteria Escherichia coli;it has certain Gram-positive bacteria Bacillus subtilis,Pseudomonas aeruginosa,Staphylococcus aureus Inhibition.The MIC values were 9.77?g/ml,78.125?g/ml and 19.5?g/ml,respectively.Seven strains with antifungal activity and antibacterial activity were selected from the soil samples for fermentation.Finally,the strain NH1835,Gao's No.1 medium,solid fermentation,and extraction with ethyl acetate were obtained.Using normal phase silica gel column chromatography,high performance liquid chromatography for separation and purification,infrared,ultraviolet,nuclear magnetic resonance and other identification of its molecular structure,obtained seven compounds,respectively,julichrome Q₁₀?1?,julichrome Q₆?2?,gliotoxin?3?,julichrome Q_6.6?4?,julichrome Q_3.5?5?,julichrome Q_5.6?6?,julichrome Q_2.3?7?.Among them,compound 1 is a new compound,which is the fourth julichrome monomer compound discovered at present,compounds 4,5,6 and 7 are julichrome dimers and compound 3 is a polythiodiketazine compound.Originally produced by Aspergillus fumigatus Gliocladium fimbriatum,we isolated from the secondary metabolites of Streptomyces for the first time in this experiment.Antimicrobial tests were performed on compounds 2,4,5,6 and 7 Antifungal experiments showed that none of the six compounds inhibited the selected seven indicator fungi.Antibacterial experiments showed that compounds 2,4,5 and 6 had certain inhibitory effects on Staphylococcus aureus,Pseudomonas aeruginosa and Escherichia coli,respectively.Among them,the inhibitory zone of compound 2 on gold,grape and patina reached 19mm and 20mm,and the inhibition was better.Compound 7 did not inhibit several indicator fungi.The cytotoxicity of compounds 1,2,4,5,6 and 7 was evaluated by MTT assay.The results showed that compounds 3 and 4 inhibited the five indicator cells,and the IC₅₀ ranged from0.11 to 15.84?M.Compound 3 inhibited the cells SMMC-7721,MCF-7 and MDA-MB-231significantly,and the IC₅₀ values were lower than the positive control drug doxorubicin.In addition,Compound 4 has a selective inhibitory effect on cells MCF-7 and MDA-MB-231,and its toxicity to normal liver cell LO2 is smaller than that of doxorubicin.