A New Isomer and Other Metabolites Isolated from Alternaria alternata

Secondary metabolite profiling of Aristolochia gigantea seeds extract by GC-EI/MS and NMR analysis

Aristolochia gigantea (Aristolochiaceae), commonly known as the Brazilian Dutchman's pipe, is cultivated globally as an ornamental vine, admired for the unique shape of its large flowers. In our ongoing research into the chemical composition of A. gigantea, the ethanol extract from its seeds was fractionated using chromatographic techniques, resulting in the isolation and identification of allantoin, along with the lignans kobusin, eudesmin, and methylarctigenin. The fractions were further analysed by NMR and GC - EI/MS, employing a molecular networking approach and retention index comparison, which led to the annotation of four sterols, eleven aliphatic alcohols, one saturated fatty acid, two unsaturated fatty acids, ten esters of saturated fatty acids, ten esters of unsaturated fatty acids, and one lactone.

Marine Natural Products from the Beibu Gulf: Sources, Chemistry, and Bioactivities

Marine natural products (MNPs) play an important role in the discovery and development of new drugs. The Beibu Gulf of South China Sea harbors four representative marine ecosystems, including coral reefs, mangroves, seaweed beds, and coastal wetlands, which are rich in underexplored marine biological resources that produce a plethora of diversified MNPs. In our ongoing efforts to discover novel and biologically active MNPs from the Beibu Gulf, we provide a systematic overview of the sources, chemical structures, and bioactive properties of a total of 477 new MNPs derived from the Beibu Gulf, citing 133 references and covering the literature from the first report in November 2003 up to September 2022. These reviewed MNPs were structurally classified into polyketides (43%), terpenoids (40%), nitrogen-containing compounds (12%), and glucosides (5%), which mainly originated from microorganisms (52%) and macroorganisms (48%). Notably, they were predominantly found with cytotoxic, antibacterial, and anti-inflammatory activities. This review will shed light on these untapped Beibu Gulf-derived MNPs as promising lead compounds for the development of new drugs.

Proposal for structural revision of several monosubstituted tricycloalternarenes

Cycloalternarenes are a group of meroterpenes isolated from epiphytic fungi with a mono-, bi, tri- or tetracyclic skeleton. We have detected in the bibliography a series of monosubstituted tricycloalternarenes with erroneous structures. Thus, in this work we make several proposals to correct the structures of nineteen 4-hydroxy-tricycloalternarenes, TCA 6a, TCA 11a₂, (2E)- and (2Z)-TCA 12a, 2H-(2E)-TCA 12a, TCAs 9a and F_2, methyl nor-tricycloalternarate, TCAs K, L, S-W, X₂ and tricycloalterfurenes A-C, and four 6-hydroxy-tricycloalternarenes, TCA 12b, TCA 13b, tricycloalterfurene D and TCA F₃. Moreover, the graphic representation of TCA 14b and TCAs 15b-18b had been corrected. In addition, we have suggested that mono-hydroxylated tricycloalternarenes can only exist in nature substituted at the 4α- or 6β-position (4R- or 6R-configuration), which could also be explained considering biogenetic reasons. We have also determined the C-4 and C-6 configuration of several monosubstituted tricycloalternarenes, whose planar structure had been previously determined. Thus, compounds of the "series a" such as TCAs 1a-8a, 11a and ACTG-toxin H have a 4R-configuration, whilst in the "series b" TCAs 3b-7b and TCAs 9b-11b possess a 6R-configuration.