Abstract
Aspergillus terreus has been reported to produce many secondary metabolites that exhibit potential bioactivities, such as antibiotic, hypoglycemic, and lipid-lowering activities. In the present study, two new thiodiketopiperazines, emestrins L (1) and M (2), together with five known analogues (3–7), and five known dihydroisocoumarins (8–12), were obtained from the marine-derived fungus Aspergillus terreus RA2905. The structures of the new compounds were elucidated by analysis of the comprehensive spectroscopic data, including high-resolution electrospray ionization mass spectrometry (HRESIMS), one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR), and electronic circular dichroism (ECD) data. This is the first time that the spectroscopic data of compounds 3, 8, and 9 have been reported. Compound 3 displayed antibacterial activity against Pseudomonas aeruginosa (minimum inhibitory concentration (MIC) = 32 μg/mL) and antifungal activity against Candida albicans (MIC = 32 μg/mL). In addition, compound 3 exhibited an inhibitory effect on protein tyrosine phosphatase 1 B (PTP1B), an important hypoglycemic target, with an inhibitory concentration (IC)50 value of 12.25 μM.
Highlights
Marine fungi, and the genus Aspergillus, have proven to be a prolific source of structurally novel and biologically active secondary metabolites that play an eminent role in drug discovery progress [1,2]
Aspergillus species, we found a series of bioactive natural products with antifungal, antibacterial, antiviral, antifouling, and
We found that compounds 2 and 3 displayed antibacterial activities against Pseudomonas aeruginosa ATCC 27853 with minimum inhibitory concentration (MIC) values of 64 μg/mL and 32 μg/mL, respectively
Summary
The genus Aspergillus, have proven to be a prolific source of structurally novel and biologically active secondary metabolites that play an eminent role in drug discovery progress [1,2]. Thiodiketopiperazines alkaloids (TDKPs) are an important class of secondary metabolites divided into nearly twenty distinct families, and characterized by the presence of a diketopiperazine core featuring thiomethyl groups and/or transannular sulfide bridges [5] These compounds have been reported to exhibit a broad range of biological properties, including immunosuppressive [6], cytotoxic [7], antibacterial [8], antiviral [9], and anti-angiogenic activities [10]. Aspergillus terreus has been reported to produce diverse secondary metabolites that display multiple bioactivities, such as antibiotic, hypoglycemic, and lipid-lowering activities [3,4,11].
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