Study Of Bioactive Secondary Metabolites From Three Marine-derived Microorganisms

Tyrosinase is an aerobic oxidase whcih plays a key role in melanin synthesis in known organisms.It is closely related to many physiological processes.Abnormal expression of Tyrosinase activity can lead to pigmentation diseases on human skin and browning of fruits and vegetables.Tyrosinase inhibitors can influence the activity of tyrosinase through competitive or non-competitive inhibition.The research and development of new tyrosinase inhibitors from marine microorganisms is of great significance in cosmetics,food and agriculture.Siderophore is a type of chelating factor synthesized by microorganisms with small molecular weight?500-1500 Da?which can specifically chelate iron ions under iron deficiency conditions.Siderophore has been applied in many fields such as biological control,medicine and plant nutrition.Siderophore can be coupled with antibiotics and release drugs in microbial cells by active transport to avoid bacterial resistance.Siderophore can be used as a new type of antibiotics.The study of deep-sea microbial ferritin can provide theoretical and experimental basis for siderophore-antibiotic coupling and help to solve the problem of bacterial resistance.Deep-sea microorganisms live in extreme environments and have unique secondary metabolic pathways.They usually secrete secondary metabolites with novel structure and significant biological activity,which can be used as an important source of new drug lead compounds.Based on the previous work in the laboratory,the strains with tyrosinase inhibitory activity or siderophore activity from deep-sea sources were studied,and the secondary metabolites of a marine microorganism were also explored.?1?In this paper,marine-derived Microbacterium binotii 40DY180 was studied.Three compounds were isolated based on anti-tyrosinase activity assay through LH-20gel column chromatography,ODS reverse chromatography and semi-preparative HPLC.The structures of compounds were identified with the help of UV-visible spectroscopy,nuclear magnetic resonance and mass spectrum.They are Micropiperazinedione A?1?,?R?-2'-?7'-Hydroxybenzyl?hydantoin?2?and Cyclo?Gly-Trp??3?.Compound 1 is a new roquefortine compound,and compounds2?3 were isolated from Microbacterium for the first time,indicating that novel and unique secondary metabolites can be generated in marine environment.Compound1?3 was evaluated for its tyrosinase inhibitory activity.Compound 1 showed weak tyrosinase inhibitory activity,compound 2 showed potent tyrosinase inhibitory activity with an IC₅₀ at 36?M.?2?Halomonas zincidurans 40DY145 was studied according to preliminary work of lab.The condition of fermentation was optimized.The isolation was guided by CAS activity through XAD-2 column and preparative HPLC.The structure of siderophore compound was identified as Amicoumacin B?4?.Compound 4 was isolated from Halomonas and reported as a siderophore compound for the first time.Compound 4 was evaluated for siderophore activity,and the results showed that compound 4 can chelate iron ions to produce a chelated compound which is insoluble in methanol,proving it has siderophore activity.?3?After fermentation of marine derived Bacillus megaterium S2,7 compounds were isolated through ethyl acetate extraction,combiflash chromatography and semi-preparativ.The structures were identified as Cyclo?Pro-Try??5?,Cyclo?Pro-Val??6?,Cyclo?Pro-Ile??7?,Cyclo?Pro-Leu??8?,Cyclo?Phe-Ile??9?,1H-Indole-3-acetic acid?10?,L-Tryptophan?11?respectively.Compounds 7 was isolated from Bacillus for the first time.Siderophore activity evaluation was performed to compound 5?11,none of them showed siderophore activity.