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Pinus eldarica is a medicinal tree used in traditional herbal medicine for the treatment of bronchial asthma and various skin diseases. As part of our ongoing search for bioactive phytochemicals with novel structures in natural products, we performed a phytochemical analysis of the methanol (MeOH) extract from P. eldarica needles collected in Iran. Phytochemical investigation of the MeOH extract, aided by liquid chromatography–mass spectrometry-based analysis, resulted in the isolation and identification of three labdane-type diterpenes ( 1–3 ), including a new and relatively unique norlabdane-type diterpene with a peroxide moiety, eldaricoxide A ( 1 ). The chemical structures of the isolated labdane-type diterpenes were elucidated by analyzing the spectroscopic data from 1D and 2D NMR and high-resolution electrospray ionization-mass spectrometry. The absolute configuration of eldaricoxide A ( 1 ) was established by employing a computational method, including electronic circular dichroism calculation and specific optical rotation. An anti- Helicobacter pylori test was conducted, where compound 3 exhibited the most potent antibacterial activity against H. pylori strain 51, inducing 72.7% inhibition (MIC 50 value of 92 μM), whereas eldaricoxide A ( 1 ) exhibited moderate antibacterial activity against H. pylori strain 51, inducing 54.5% inhibition (MIC 50 value of 95 μM). These findings demonstrated that the identified bioactive labdane-type diterpenes 1 and 3 can be applied in the development of novel antibiotics against H. pylori for the treatment of gastric and duodenal ulcers.

Streptomyces spp. are well-known symbiotic microorganisms that produce antimicrobial metabolites against various pathogens. We isolated actinomycetes from the body surface of the termite Odontotermes formosanus and identified it as Streptomyces neopeptinius BYF101 based on 16S rRNA phylogenetic analysis. Chemical analysis of the cultures of termite-associated S. neopeptinius BYF101 via HR-MS2 and GNPS analyses enabled the isolation and identification of 20 metabolites, including the unreported obscurolide-type metabolites (1–3). The chemical structures of unreported compounds (1–3) were elucidated using HR-ESI-MS and 1D and 2D NMR analysis, and their absolute configurations were determined via chemical reactions followed by the application of competing enantioselective acylation (CEA) and computational methods for ECD and DP4+ probability calculation. The isolated compounds (1–20) were tested to determine their antifungal activity against two human fungal pathogens, Candida albicans and Cryptococcus neoformans. Among the compounds tested, indole-3-carboxylic acid (9) displayed antifungal activity against C. neoformans, with an MIC value of 12 μg/mL.

As part of an ongoing natural product chemical research for the discovery of bioactive secondary metabolites with novel structures, wild fruiting bodies of Daedaleopsis confragosa were collected and subjected to chemical and biological analyses. We subjected the fractions derived from the methanol extract of the fruiting bodies of D. confragosa to bioactivity-guided fractionation because the methanol extract of D. confragosa showed antibacterial activity against Helicobacter pylori strain 51, according to our bioactivity screening. The n-hexane and dichloromethane fractions showed moderate to weak antibacterial activity against H. pylori strain 51, and the active fractions were analyzed for the isolation of antibacterial compounds. Liquid chromatography-tandem mass spectrometry (LC–MS/MS) analysis revealed that the n-hexane fraction contains several compounds which are absent in the other fractions, so the fraction was prioritized for further fractionation. Through chemical analysis of the active n-hexane and dichloromethane fractions, we isolated five ergosterol derivatives (1–5), and their chemical structures were determined to be demethylincisterol A3 (1), (20S,22E,24R)-ergosta-7,22-dien-3β,5α,6β-triol (2), (24S)-ergosta-7-ene-3β,5α,6β-triol (3), 5α,6α-epoxy-(22E,24R)-ergosta-7,22-dien-3β-ol (4), and 5α,6α-epoxy-(24R)-ergosta-7-en-3β-ol (5) by NMR spectroscopic analysis. This is the first report on the presence of ergosterol derivatives (1–5) in D. confragosa. Compound 1 showed the most potent anti-H. pylori activity with 33.9% inhibition, rendering it more potent than quercetin, a positive control. Compound 3 showed inhibitory activity comparable to that of quercetin. Distribution analysis of compound 1 revealed a wide presence of compound 1 in the kingdom Fungi. These findings indicate that demethylincisterol A3 (1) is a natural antibiotic that may be used in the development of novel antibiotics against H. pylori.

Stereocalpin B, a new cyclic depsipeptide (1), and a new dibenzofuran derivative (3), were isolated from the Antarctic lichen, Ramalina terebrata (Ramalinaceae), along with a known cyclic depsipeptide (2). The structures of new compounds were characterized by comprehensive spectrometric analyses; high-resolution fast atom bombardment mass spectrometry (HR-FABMS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Stereocalpin B (1) existed in a rotameric equilibrium, which was confirmed using nuclear Overhauser effect spectroscopy (NOESY)/exchange spectroscopy (EXSY) spectrum. Absolute configurations of the amino acid units in 1 were assigned using the advanced Marfey’s method and subsequent NOESY analysis of the 5-hydroxy-2,4-dimethyl-3-oxo-decanoic acid residue confirmed the complete stereochemistry of 1. Compounds 1-3 exhibited moderate antimicrobial activities against E. coli, with the IC50 values ranging from 18‒30 μg/mL. Compound 2 exhibited cell growth inhibition against HCT116 cell lines, with the IC50 value of 20 ± 1.20 μM, and compounds 1 and 2 also showed potent anti-inflammatory activities against lipopolysaccharide (LPS)-induced RAW264.7 macrophages with the IC50 values ranging from 5‒7 μM.

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Three isoindolinone alkaloids (1−3), including one new isoindolinone-type alkaloid, meyeroguilline E (1), and six other known compounds (4−9) were isolated from the poisonous mushroom Chlorophyllum molybdites (Agaricaceae). The structure of the new compound was determined using extensive spectroscopic analyses via one-dimensional (1D) and two-dimensional (2D) NMR data interpretation and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). To the best of our knowledge, compound 1 is the first example of a natural isoindolinone with a butanoic acid moiety, and this study is the first to detect the other known compounds (2−9) in C. molybdites. The isolated compounds (1−9) were examined for their multidrug resistance (MDR) reversal activity against MES-SA, MES-SA/DX5, HCT15, and HCT15/CL02 human cancer cells. Based on the results, 20 μM of compounds 3 and 6 slightly potentiated paclitaxel (TAX)-induced cytotoxicity in MES-SA/ DX5, HCT15, and HCT15/CL02 cells; however, the compounds had no effect on the cytotoxicity against MES-SA and nonMDR cells.