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An extensive phytochemical study of a foliose lichen from Indonesia, Parmelia cetrata, resulted in the successful isolation of 13 phenol and depside derivatives (1–13) including the previously unre...

High-performance thin-layer chromatography (HPTLC) coupled with negative ion desorption electrospray ionization high-resolution mass spectrometry (DESI-HRMS) was used for the analysis of anthraquinones in complex crude extracts of Chilean dermocyboid Cortinarii. For this proof-of-concept study, the known anthraquinones emodin, physcion, endocrocin, dermolutein, hypericin, and skyrin were identified by their elemental composition. HRMS also allowed the differentiation of the investigated anthraquinones from accompanying compounds with the same nominal mass in the crude extracts. An investigation of the characteristic fragmentation pattern of skyrin in comparison with a reference compound showed, exemplarily, the feasibility of the method for the determination of these coloring, bioactive and chemotaxonomically important marker compounds. Accordingly, we demonstrate that the coupling of HPTLC with DESI-HRMS represents an advanced and efficient technique for the detection of anthraquinones in complex matrices. This analytical approach may be applied in the field of anthraquinone-containing food and plants such as Rheum spp. (rhubarb), Aloe spp., Morinda spp., Cassia spp. and others. Furthermore, the described method can be suitable for the analysis of anthraquinone-based colorants and dyes, which are used in the food, cosmetic, and pharmaceutical industry.

A multicomponent macrocyclization strategy towards cyclic lipopeptides is described. The approach relies on the utilization of the Ugi and Passerini multicomponent reactions for the cyclization of peptides and oxo-peptides, and here it is employed for the construction of a small library of analogues of the natural products mycosubtilin and surfactin A. A key feature of this method is the simultaneous incorporation of either one or two exocyclic lipid tails along with the macrocyclic ring closure, which is only possible due to the multicomponent nature of the macrocyclization step. The evaluation of the anticancer activity of the lipopeptide library showed that the installation of a second lipid moiety in the surfactin scaffold leads to a more potent cytotoxicity in cancer cells. This is a new example of the multicomponent reaction potential in rapidly producing natural product analogues for biological screening.

A new multicomponent methodology for the solution- and solid-phase macrocyclization of peptides is described. The approach comprises the utilization of the Ugi–Smiles reaction for the cyclization of 3-nitrotyrosine-containing peptides either by the N-terminus or the lysine side-chain amino groups. Both the on-resin and solution cyclizations took place with good to excellent efficiency in the presence of an aldehyde and a lipidic isocyanide, while the use of paraformaldehyde required an aminocatalysis-mediated imine formation prior to the on-resin Ugi–Smiles ring closure. The introduction of a turn motif in the peptide sequence facilitated the cyclization step, shortened the reaction time, and delivered crude products with >90% purity. This powerful method provided a variety of structurally novel N-aryl-bridged cyclic lipopeptides occurring as single atropisomers.

The Chilean Sepedonium aff. chalcipori strain KSH 883, isolated from the endemic Boletus loyo Philippi, was studied in a polythetic approach based on chemical, molecular, and biological data. A taxonomic study of the strain using molecular data of the ITS, EF1-α, and RPB2 barcoding genes confirmed the position of the isolated strain within the S. chalcipori clade, but also suggested the separation of this clade into three different species. Two new linear 15-residue peptaibols, named chilenopeptins A (1) and B (2), together with the known peptaibols tylopeptins A (3) and B (4) were isolated from the semisolid culture of strain KSH 883. The structures of 1 and 2 were elucidated on the basis of HRESIMS(n) experiments in conjunction with comprehensive 1D and 2D NMR analysis. Thus, the sequence of chilenopeptin A (1) was identified as Ac-Aib(1)-Ser(2)-Trp(3)-Aib(4)-Pro(5)-Leu(6)-Aib(7)-Aib(8)-Gln(9)-Aib(10)-Aib(11)-Gln(12)-Aib(13)-Leu(14)-Pheol(15), while chilenopeptin B (2) differs from 1 by the replacement of Trp(3) by Phe(3). Additionally, the total synthesis of 1 and 2 was accomplished by a solid-phase approach, confirming the absolute configuration of all chiral amino acids as l. Both the chilenopeptins (1 and 2) and tylopeptins (3 and 4) were evaluated for their potential to inhibit the growth of phytopathogenic organisms.

Four new 19-residue peptaibols, named tulasporins A–D (1–4), were isolated from the semi-solid cultures of Sepedonium tulasneanum. Their structures were elucidated on the basis of extensive ESI-HRMSn fragmentation studies as well as 1H NMR spectroscopic analyses. Interestingly, the structures of tulasporins A–D (1–4) resemble those of chrysospermins isolated earlier from cultures of S. chrysospermum. Previously, it was hypothesized that the peptaibol production by Sepedonium species correlates with the morphology of the aleurioconidia, as exclusively round-shaped aleurioconidia forming species produced peptaibols. Since the investigated Sepedonium tulasneanum produces oval aleurioconidia, this study can be considered as the first report of peptaibols from a Sepedonium strain with oval-shaped aleurioconidia. Thus, it could be demonstrated that both round as well as oval aleurioconidia forming Sepedonium species are able to produce peptaibols. Tulasporins A-D (1–4), when tested against phytopathogenic fungi, exhibited good growth inhibitory activity against both Botrytis cinerea and Phytophthora infestans, while they were devoid of significant activity against Septoria tritici.