Journal of Natural Products 最新文献

Ibrexafungerp, an inhibitor of fungal β-(1,3)-d-glucan synthase, represents the first new class of antifungals to be approved in the last 20 years. Ibrexafungerp is a semisynthetic derivative of the naturally occurring triterpene glycoside enfumafungin. In order to search for new analogues of enfumafungin and to probe its biosynthesis, we undertook a reinvestigation of Hormonema carpetanum, which led to the isolation of two new analogues, enfumafungins B and C, together with enfumafungin. Due to the presence of a hemiacetal moiety in the structure, the enfumafungins appear as a mixture of two interconverting epimers during both the purification process and NMR data acquisition. The structure elucidation, including the differentiation of 25S* and 25R* epimers, was completed by combined analyses of NMR and MS spectroscopic data. The discovery of enfumafungins B and C may have implications for enfumafungin biosynthesis. The antifungal activity of enfumafungins B and C was significantly lower than that of enfumafungin, suggesting that the C-2 substituents and the C-19 carboxy acid are important for activity. Molecular docking simulations revealed significant hydrogen bond interactions between enfumafungins and β-(1,3)-d-glucan synthase, which may be useful for developing new antifungal agents.

The DNAJB1–PRKACA oncogenic gene fusion results in an active kinase enzyme, J-PKAcα, that has been identified as an attractive antitumor target for fibrolamellar hepatocellular carcinoma (FLHCC). A high-throughput assay was used to identify inhibitors of J-PKAcα catalytic activity by screening the NCI Program for Natural Product Discovery (NPNPD) prefractionated natural product library. Purification of the active agent from a single fraction of an Aplidium sp. marine tunicate led to the discovery of two unprecedented alkaloids, aplithianines A (1) and B (2). Aplithianine A (1) showed potent inhibition against J-PKAcα with an IC₅₀ of ∼1 μM in the primary screening assay. In kinome screening, 1 inhibited wild-type PKA with an IC₅₀ of 84 nM. Further mechanistic studies including cocrystallization and X-ray diffraction experiments revealed that 1 inhibited PKAcα catalytic activity by competitively binding to the ATP pocket. Human kinome profiling of 1 against a panel of 370 kinases revealed potent inhibition of select serine/threonine kinases in the CLK and PKG families with IC₅₀ values in the range ∼11–90 nM. An efficient, four-step total synthesis of 1 has been accomplished, enabling further evaluation of aplithianines as biologically relevant kinase inhibitors.

Four previous papers reported the isolation and structural determination of 10 polycyclic polyprenylated acylphloroglucinols (PPAPs), uraliones F, G, K, and O, attenuatumiones E and F, and scabrumiones A–D, from Hypericum species. Their structures were identified as type B PPAPs that featured not only the characteristic acyl group at C-3 of the bicyclo[3.3.1]nonane core but also a partly reduced furan ring fused to the C-1–C-2–O-2 atoms of the core. However, the 1D and 2D NMR data of these compounds were more consistent with type A PPAPs that featured not only the acyl group at C-1 but also a partially reduced furan ring fused to the C-3–C-2–O-2 atoms of the core. Now we revise these 10 previously proposed structures to the corresponding type A PPAPs via NMR analysis. Additionally, we propose a rule that uses NMR data to determine whether a particular PPAP that is fused to a partly reduced furan ring at C-3–C-2–O-2 or C-1–C-2–O-2 is type A or type B, respectively. We also propose a rule to assign the relative configurations of corresponding type A PPAPs at C-18 and revise the configurations of sampsonione N, hypericumoxides A–C, and hyperscabin G.

Linaridins are a family of underexplored ribosomally synthesized and post-translationally modified peptides despite the prevalence of their biosynthetic gene clusters (BGCs) in microbial genomes, as shown by bioinformatic studies. Our genome mining efforts reveal that 96 putative oxidoreductase genes, namely, LinC, are encoded in linaridin BGCs. We heterologously expressed two such LinC-containing linaridin BGCs, yan and ydn, from Streptomyces yunnanensis and obtained three new linaridins, named yunnanaridins A–C (1–3). Their structures are characterized by Z-configurations of the dehydrobutyrines and the presence of a variety of epimerized amino acid residues. Yunnanaridin A (1) is the sixth member of the family of type-B linaridins, whereas yunnanaridins B (2) and C (3) represent the first examples of expressed type-C linaridins. Interestingly, heterologous expression of the same BGCs with LinC in-frame knockouts produced the same compounds. This work expands the structural diversity of linaridins and provides evidence for the notion that the widespread LinCs may not be involved in linaridin biosynthesis.

Investigation of cultivated fruiting bodies of Ganoderma weberianum led to the isolation of 11 previously unreported lanostane dimers, ganoweberianones C (3a), D (4a), E (5a), F (6a), G (7a), and H (8a) and isoganoweberianones A (1b), B (2b), D (4b), G (7b), and H (8b). Six new ganodermanontriol derivatives as three pairs of diastereomers (11/12, 13/14, and 15/16) and five new ganoweberianic acids (17–21) were also isolated. A method for semisynthesis of lanostane dimers by condensation of natural lanostanes was established, which was utilized in the structure elucidation and NMR data assignments of the undescribed natural lanostane dimers. Ganoweberianone D (4a) and isoganoweberianone D (4b) showed significant antimalarial activity against Plasmodium falciparum K1 (multidrug-resistant strain) with IC₅₀ values of 0.057 and 0.035 μM, respectively, whereas their cytotoxicity to Vero cells was weaker (IC₅₀ 8.1 and 19 μM, respectively).

Four new aranotin-type epipolythiodioxopiperazines, graphiumins K–N (1–4), along with four known analogues (5–8), were isolated from the deep-sea-derived fungus Exophiala mesophila MCCC 3A00939. Their structures were elucidated by detailed interpretation of NMR and mass spectrometric data. The absolute configuration of the isolates was deduced by a single-crystal X-ray diffraction analysis and the comparisons of experimental electronic circular dichroism (ECD) data with calculated ECD spectra. Graphiumins K (1) and L (2) exhibited cytotoxic activities against the K562, H69AR, and MDA-MB-231 cancer cells with IC₅₀ values ranging from 2.3 to 5.9 μM.

Euphorbia diterpenoids possess inhibitory effects of Kv1.3 ion channel, but most of this research has focused on diterpenoids with jatrophane-related or ingenane-related skeletons. In the present study, nine undescribed (1–9) and 16 known (10–25) diterpenoids, based on jatrophane, lathyrane, ingenane, abietane, and atisane skeletons, were identified from the methanol extract of the aerial parts of Euphorbia fischeriana. The structures were established by analysis of the spectroscopic data as well as by single-crystal X-ray diffraction analysis. Among the isolated diterpenoids, macrocyclic jatrophanes and lathyranes exerted Kv1.3 blocking activity. Compound 8 exhibited good selectivity on the inhibition of the Kv 1.3 channel rather than hERG channel, with a selectivity index over 7.0. The selective activity of lathyrane diterpenoids indicates that macrocyclic diterpenoids have the potential to be further investigated as therapeutic agents for the treatment of autoimmune diseases.

The stereoselective total synthesis of dechlorotrichotoxin A, alongside the synthesis of a 1:1 10E/Z mixture of trichotoxin A, was successfully achieved, commencing from the natural monoterpenoid (−)-citronellal. Key steps in the synthesis involved introducing three alkenes and establishing a stereogenic secondary alcohol center. These transformations were accomplished through olefin cross-metathesis, Tebbe olefination, and enantioselective allylation using a chiral phosphoric acid. A comparison of the spectroscopic data between the synthetic dechlorotrichotoxin A and the reported spectra confirmed that the polyketide isolated from a Smenospongia species corresponds to trichotoxin A rather than dechlorotrichotoxin A.

Persea americana Mill. (Lauraceae), commonly known as avocado, is a well-known food because of its nutrition and health benefits. The seeds of avocado are major byproducts, and thus their phytochemicals and bioactivities have been of interest for study. The chemical components of avocado seeds were investigated by using UPLC-qTOF-MS/MS-based molecular networking, resulting in the isolation of seven new oxindole alkaloids (1–7) and two new benzoxazinone alkaloids (8 and 9). The chemical structures of the isolated compounds were identified by the analysis of NMR data in combination with computational approaches, including NMR and ECD calculations. Bioactivities of the isolated compounds toward silent information regulation 2 homologue-1 (SIRT1) in HEK293 cells were assessed. The results showed that compound 1 had the most potent effect on SIRT1 activation with an elevated NAD⁺/NADH ratio with potential for further investigation as an anti-aging agent.

The first semisynthetic routes toward terrestrial anti-inflammatory natural products linariophyllene A–C and the refined route toward marine natural product rumphellolide H are presented. Among the synthesized target compounds, the correct structure of linariophyllene A was determined to be the diastereomer of the originally proposed structure with an inverted stereocenter at the secondary alcohol. The proposed structures of linariophyllene B and rumphellolide H were confirmed. However, the correct structure of linariophyllene C was found to be the diastereomer of the originally proposed structure with an inverted stereocenter at the tertiary carbon of the epoxide moiety. The structures of linariophyllenes A–C and rumphellolide H were unequivocally confirmed by single-crystal X-ray diffractometry. The obtained results enabled the proposal of the biosynthetic origins of the aforementioned natural products and bolstered the diversity of available sesquiterpenoids. Linariophyllenes A–C and rumphellolide H were obtained in sufficient amounts to further expand their bioactivity profile and utility as reference standards in future studies of chemical constituents of terrestrial and marine organisms.