Five
new unusual citrinin-derived alkaloids with a tetracyclic
core, citrinidines A–E (1–5), two new amide alkaloids, methyl (2S,8E)-1′-(2-methyl-3-oxodec-8-enamido) butanoate (6) and (2S,8E)-2-methyl-3-oxodec-8-enamide
(7), a new unusual citrinin trimer, tricitrinol C (8), a new citrinin acetal-ketal derivative, citrininol (9), together with four known citrinin monomers (10–13), and three known citrinin dimers (14–16), were isolated from the fermentation of hydrothermal
vent-associated fungus Penicillium citrinum TW132-59. Their structures were unambiguously determined by nuclear
magnetic resonance (NMR), mass spectrometry, Mosher′s method, 13C NMR calculation in combination with DP4+, and ECD calculations.
A plausible biosynthetic pathway of all new compounds (1–9) was proposed. Citrinin trimer (8) exhibited potent cytotoxicity activity with an IC50 value
of 1.34 ± 0.11 μM, and compounds 1 and 15 showed moderate cytotoxicity with IC50 values
of 17.50 ± 1.43 and 9.45 ± 0.55 μM, respectively,
against A549 cell line.
Aporphine alkaloids, characterized by a heterocyclic aromatic basic skeleton, are known from different organisms and exhibit various biological activities: anti-tumor, anti-viral, anti-microbial, anti-inflammatory etc. The review gives information which provides an overview of the latest progress in the structural diversity and the biological activity of the aporphine alkaloids with their derivatives isolated from natural resource in recent years. Additionally, the synthetic approaches of aporphine alkaloids have also been reviewed.
In nature, secondary metabolites have been proven to be the essential communication media between co-occurring microorganisms and to influence their relationship with each other. In this study, we conducted a metabolomics survey of the secondary metabolites of an artificial co-culture related to a hydrothermal vent fungal–bacterial community comprising Aspergillus sclerotiorum and Streptomyces and their reciprocal relationship. The fungal strain was found to increase the secretion of notoamides and the compound cyclo(Pro-Trp) produced by the actinomycetes strain was discovered to be the responsible molecule. This led to the hypothesis that the fungi transformed cyclo(Pro-Trp) synthesized by the actinomycetes as the biosynthetic precursors of notoamides in the chemical communication. Further analysis showed Streptomyces sp. WU20 was efficient in transforming amino acids into cyclo(Pro-Trp) and adding tryptophan as well as proline into the chemical communication enhanced the induction of the notoamide accumulation. Thus, we propose that the microbial transformation during the synthetic metabolically-mediated chemical communication might be a promising means of speeding up the discovery of novel bioactive molecules. The objective of this research was to clarify the mechanism of microbial transformation for the chemical communication. Besides, this research also highlights the utility of mass spectrometry-based metabolomics as an effective tool in the direct biochemical analysis of community metabolites.
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