![]() ![]() Didymellanosine is the first 13-membered macrocyclic alkaloid with a cyclopentafluorene ring system conjugated with adenosine. (16) Recently, ascomylactams A–C (17) and didymellanosine (18) were characterized and reported to exhibit cytotoxic and antimicrobial activities. Phomapyrrolidones A–C were reported concurrently and found to exhibit weak antitubercular activity. (14) Embellicines A and B, reported in 2013, have a tetracyclic core fused with a 13-membered macrocycle, (15) and their cytotoxic properties were purported to be due to TNFα-induced NF-κB transcriptional activity. To date, only ten have been reported, and all of those have been isolated from endophytic fungi. (14) However, alkaloids with a cyclopentafluorene (6/5/6/5) ring system are relatively new to the literature. ![]() (11−13) The Dictionary of Natural Products reports the isolation of more than 30 000 alkaloids from various natural sources. Compounds 1 and 5 were also cytotoxic against human ovarian (OVCAR3) and melanoma (MDA-MB-435) cancer cell lines.Īlkaloids, in particular, are a highly diverse class of natural products that exhibit a wide range of pharmacological properties. These alkaloids ( 1– 5) showed cytotoxic activity against a human breast cancer cell line (MDA-MB-231) that ranged from 0.4 to 4.8 μM. The relative configurations of these molecules were established via 1H– 1H coupling constants and nuclear Overhauser effect spectroscopy, while comparisons of the experimental electronic circular dichroism (ECD) spectra with the time-dependent density functional theory ECD calculations were utilized to assign their absolute configurations, which were in good agreement with the literature. The structures were identified by examining both high-resolution electrospray ionization mass spectrometry data and one-dimensional and two-dimensional NMR spectra. (fungal strain MSX6737) led to a series of both known and new members of this structural class ( 1– 5), including the known embellicine A ( 1), three new embellicine analogues ( 2, 4, and 5), and a semisynthetic acetylated analogue ( 3). Bioassay-guided fractionation of a Sarocladium sp. Macrocyclic alkaloids with a cyclopentafluorene ring system are a relatively young structural class of fungal metabolites, with the first members reported in 2013. ![]()
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