Abstract
The mangrove ecosystem is a rich resource for the discovery of actinomycetes with potential applications in pharmaceutical science. Besides the genus Streptomyces, Micromonospora is also a source of new bioactive agents. We screened Micromonospora from the rhizosphere soil of mangrove plants in Fujian province, China, and 51 strains were obtained. Among them, the extracts of 12 isolates inhibited the growth of human lung carcinoma A549 cells. Strain 110B exhibited better cytotoxic activity, and its bioactive constituents were investigated. Consequently, three new isoflavonoid glycosides, daidzein-4′-(2-deoxy-α-l-fucopyranoside) (1), daidzein-7-(2-deoxy-α-l-fucopyranoside) (2), and daidzein-4′,7-di-(2-deoxy-α-l-fucopyranoside) (3) were isolated from the fermentation broth of strain 110B. The structures of the new compounds were determined by spectroscopic methods, including 1D and 2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry (HR-ESIMS). The result of medium-changing experiments implicated that these new compounds were microbial biotransformation products of strain M. aurantiaca 110B. The three compounds displayed moderate cytotoxic activity to the human lung carcinoma cell line A549, hepatocellular liver carcinoma cell line HepG2, and the human colon tumor cell line HCT116, whereas none of them showed antifungal or antibacterial activities.
Highlights
The mangrove ecosystem, distinguished by its land-to-ocean transition, is complex and special.Mangroves thrive in a stressful environment of high salinity, high moisture, strong winds, and high osmotic pressure [1]
Fifty-one strains belonging to the genus Micromonospora were isolated from mangrove soil
The results showed that the isolates belonged to seven rRNA genes of the 12 strains were sequenced and the sequences were blasted against GenBank different species (Figure 2) and that strain 110B was closely related to the type strain Micromonospora
Summary
Mangroves thrive in a stressful environment of high salinity, high moisture, strong winds, and high osmotic pressure [1]. This environment breeds a distinctive microbial community that can tolerate numerous stresses and has developed unique metabolic pathways for the purpose of structural ecological adaptability [2,3]. Recent research has focused on the diversity of mangrove microorganisms and their metabolic compounds [4,5,6]. Actinomycetes have gained more attention due to their ability to produce impressive numbers of bioactive metabolites [3]. There is clear evidence that the mangrove ecosystem contains a large diversity of actinomycetes [7].
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