Koji Yamada

A reexamination of the reported structure of isomallotusinin, previously proposed as an anomer of the ellagitannin mallotusinin, demonstrates that this compound is identical to mallotusinin, thus correcting a structural misassignment. This conclusion is supported by a detailed conformational analysis of mallotusinin, which bears a distinctive tetrahydroxydibenzofuranoyl (THDBF) group. Through a DFT-assisted analysis of 1H–1H coupling constants, we demonstrate that mallotusinin exists as a solvent-dependent equilibrium of 3S1 and 1C4 conformers. Our findings resolve a structural ambiguity in the literature and highlight the importance of considering conformational dynamics in the structural elucidation of conformationally flexible ellagitannins.

Brevipetins E and F, ellagitannin dimers from Cleidion brevipetiolatum, were originally reported to bear both a 3,4-(Ra)-hexahydroxydiphenoyl (HHDP)-glucopyranose and a 3,4-(Ra)-HHDP-rhamnopyranose moiety. However, a detailed reevaluation of the reported electronic circular dichroism (ECD) data, supported by DFT-based 1H and 13C NMR chemical shift and ECD calculations, supports a stereochemical reassignment of these ellagitannins. Accordingly, the 3,4-HHDP-rhamnopyranose moiety in these compounds is reassigned to the (Sa)-atropisomeric configuration, in line with the observed reduction in Δε magnitudes relative to the constituent monomers.

Ellagitannin dimers, 1,1′;2,2′-diHHDP-diglucose and 3,3′;4,4′-diHHDP-6,6′-digalloyl-diglucose, were recently isolated from the wood of the sweet chestnut (Castanea sativa Mill.). These compounds were originally reported to possess unprecedented macrocyclic dimeric structures bridged by two hexahydroxydiphenoyl (HHDP) groups. However, reinvestigation of their spectroscopic data revealed that these compounds correspond to known ellagitannin monomers, namely 2,3-O-(Sa)-HHDP-D-glucopyranose and gemin D (3-O-galloyl-4,6-O-(Sa)-HHDP-D-glucopyranose), respectively. A comparison of the originally reported NMR data for 1,1′;2,2′-diHHDP-diglucose and 3,3′;4,4′-diHHDP-6,6′-digalloyl-diglucose with those of authentic 2,3-O-(Sa)-HHDP-D-glucopyranose and gemin D, in combination with DFT-based NMR chemical shift calculations, unequivocally confirmed these structural revisions.

Cancer is the leading cause of death globally, with an increasing number of cases being annually reported. Nature-derived metabolites have been widely studied for their potential programmed necrosis, cytotoxicity, and anti-proliferation leading to enrichment for the modern medicine, particularly within the last couple of decades. At a more rapid pace, the concept of multi-target agents has evolved from being an innovative approach into a regular drug development procedure for hampering the multi-fashioned pathophysiology and high-resistance nature of cancer cells. With the advent of the Red Sea Penicillium chrysogenum strain S003-isolated indole-based alkaloids, we thoroughly investigated the molecular aspects for three major metabolites: meleagrin (MEL), roquefortine C (ROC), and isoroquefortine C (ISO) against three cancer-associated biological targets Cdc-25A, PTP-1B, and c-Met kinase. The study presented, for the first time, the detailed molecular insights and near-physiological affinity for these marine indole alkaloids against the assign targets through molecular docking-coupled all-atom dynamic simulation analysis. Findings highlighted the superiority of MEL’s binding affinity/stability being quite in concordance with the in vitro anticancer activity profile conducted via sulforhodamine B bioassay on different cancerous cell lines reaching down to low micromolar or even nanomolar potencies. The advent of lengthy structural topologies via the metabolites’ extended tetracyclic cores and aromatic imidazole arm permitted multi-pocket accommodation addressing the selectivity concerns. Additionally, the presence decorating polar functionalities on the core hydrophobic tetracyclic ring contributed compound’s pharmacodynamic preferentiality. Introducing ionizable functionality with more lipophilic characters was highlighted to improve binding affinities which was also in concordance with the conducted drug-likeness/pharmacokinetic profiling for obtaining a balanced pharmacokinetic/dynamic profile. Our study adds to the knowledge regarding drug development and optimization of marine-isolated indole-based alkaloids for future iterative synthesis and pre-clinical investigations as multi-target anticancer agents.

Different extracts of the Bamboo shoot skin Phyllostachys heterocycla var. pubescens were screened against panel of cancer cell lines and normal one. The cell viability results exhibited that the ethyl acetate extract showed the least vitality percentage of 2.14% of HepG2 cells. Accordingly, it was subjected to chromatographic separation, which resulted in the isolation of a new natural product; 7-hydroxy, 5-methoxy, methyl cinnamate (1), together with four known compounds. The structures of the pure isolated compounds were deduced based on different spectroscopic data. The new compound (1) was screened against the HepG2 and MCF-7 cells and showed IC₅₀ values of 7.43 and 10.65 µM, respectively. It induced apoptotic cell death in HepG2 with total apoptotic cell death of 58.6% (12.44-fold) compared to 4.71% in control by arresting cell cycle progression at the G1 phase. Finally, compound 1 was validated as EGFR tyrosine kinase inhibitor in both enzymatic levels (IC₅₀ = 98.65 nM compared to Erlotinib (IC₅₀ = 78.65 nM). Finally, in silico studies of compound 1 through the molecular docking indicated its high binding affinity towards EGFR protein and the ADME pharmacokinetics indicated it as a drug-like.

Phytochemical screening of nonpolar fractions from the methanol extract of the Bamboo shoot skin Phyllostachys heterocycla var. pubescens resulted in the isolation of a new sterol-glucoside-fatty acid derivative (6’-O-octadeca-8″,11″-dienoyl)-sitosterol-3-O-β-d-glucoside (1), together with six known compounds. The chemical structures of the pure isolated compounds were deduced based on different spectral data. The isolated compounds were assessed to determine their cytotoxic activity, and the results were confirmed by determining their apoptotic activity. Compound 1 was more cytotoxic against the MCF-7 cells (IC₅₀ = 25.8 µM) compared to Fluorouracil (5-FU) (26.98 µM), and it significantly stimulated apoptotic breast cancer cell death with 32.6-fold (16.63% compared to 0.51 for the control) at pre-G1 and G2/M-phase cell cycle arrest and blocked the progression of MCF-7 cells. Additionally, RT-PCR results further confirmed the apoptotic activity of compound 1 by the upregulation of proapoptotic genes (P53; Bax; and caspases 3, 8, and 9) and downregulation of the antiapoptotic genes (BCL2). Finally, the identified compounds, especially 1, were found to have high binding affinity towards both tyrosine-specific protein kinase (TPK) and vascular endothelial growth factor receptor (VEGFR-2) through the molecular docking studies that highlight its mode of action.

Bioactivity-guided isolation supported by LC-HRESIMS metabolic profiling led to the isolation of two new compounds, a ceramide, stylissamide A (1), and a cerebroside, stylissoside A (2), from the methanol extract of the Red Sea sponge Stylissa carteri. Structure elucidation was achieved using spectroscopic techniques, including 1D and 2D NMR and HRMS. The bioactive extract’s metabolomic profiling showed the existence of various secondary metabolites, mainly oleanane-type saponins, phenolic diterpenes, and lupane triterpenes. The in vitro cytotoxic activity of the isolated compounds was tested against two human cancer cell lines, MCF-7 and HepG2. Both compounds, 1 and 2, displayed strong cytotoxicity against the MCF-7 cell line, with IC₅₀ values at 21.1 ± 0.17 µM and 27.5 ± 0.18 µM, respectively. They likewise showed a promising activity against HepG2 with IC₅₀ at 36.8 ± 0.16 µM for 1 and IC₅₀ 30.5 ± 0.23 µM for 2 compared to the standard drug cisplatin. Molecular docking experiments showed that 1 and 2 displayed high affinity to the SET protein and to inhibitor 2 of protein phosphatase 2A (I2PP2A), which could be a possible mechanism for their cytotoxic activity. This paper spreads light on the role of these metabolites in holding fouling organisms away from the outer surface of the sponge, and the potential use of these defensive molecules in the production of novel anticancer agents.

Very recently, the immunotherapies against cancer, autoimmune diseases, and infection have been feasible and promising. Thus, we have examined the possibility whether or not human gamma delta T cells can be applied for the novel immunotherapies. We previously established the cells stably maintaining NFkB-driven human secreted embryonic alkaline phosphatase (SEAP) expression. The cells can be used to determine the transcription activity of NFkB with high-standard dynamic range and accuracy. Because IL-18 is a kind of cytokines that enhances cytotoxicity and activity of human gamma delta T cells through NFkB activation, we have focused on the activity and signaling of IL-18. In this study, we modified the previous reporter cell that can determine the transcription activity of NFkB to express two subunits consisted of human IL-18 receptor. The modified cells secreted SEAP in response to treatment with human recombinant IL-18 in a concentration-dependent manner. We also observed the concentration-dependently enhancement of NFkB activity in the cells treated with mouse recombinant IL-18 although the affinity was lower compared to human recombinant IL-18. We also previously established the cells stably expressing and secreting human recombinant IL-18 and then validated whether or not the conditioned medium from the cells activate NFkB transcription activity using this assay. Our university has kept collecting many extracts from over 18,000 marine bacteria in our local sea around Omura bay—fungi, plants for Chinese herbal medicine, and so on—and also have kept gathering synthetic compounds from many Japanese chemists as drug libraries. Finally, in order to identify drugs mimicking IL-18 biological activity or possessing inhibitory effects on IL-18-induced NFkB, we demonstrated drug screening using number of extracts derived from marine bacteria and synthetic compounds.

A new cyclic depsipeptide (1) has been isolated from culture broth of Staphylococcus sp. (No. P-100826-4-6) derived from Corallina officinalis L., together with the known compounds indol-3-carboxylic acid (2), 1,5-dideoxy-3-C-methyl arabinitol (3), thymine (4), uracil (5), cyclo (L-pro-L-omet) (6) and macrolactin B (7). The structure of (1) was established to be cyclo (2α, 3-diaminopropoinc acid-L-Asn-3-β-hydroxy-5-methyl-tetradecanoic acid-L-Leu¹-L-Asp-L-Val-L-Leu²-L-Leu³) by extensive spectroscopic techniques including ¹H NMR, ¹³C NMR, ¹H‒¹H COSY, HMBC, HSQC, NOESY, and HRFABMS. The antimicrobial activities of compounds 1–7 were evaluated. Compounds 1–5, and 7 showed moderate antimicrobial activity while compound 6 exhibited a potent antimicrobial and antifungal activities.

The liability of the H-2-receptor antagonist nizatidine (NZ) to nitrosation in simulated gastric juice (SGJ) and under WHO-suggested conditions was investigated for the first time. For monitoring the nitrosatability of NZ, a hydrophilic interaction liquid chromatography (HILIC) method was optimized and validated according to FDA guidance. A Cosmosil HILIC (R) column and a mobile phase composed of acetonitrile: 0.04 M acetate buffer pH 6.0 (92:8, v/v) were used for the separation of NZ and its N-nitroso derivative (NZ-NO) within 6 min with LODs of 0.02 and 0.1 mu g/mL, respectively. NZ was found highly susceptible to nitrosation in SGJ reaching 100% nitrosation in 10 min, while only 18% nitrosation was observed after 160 min under the WHO-suggested conditions. The chemical structure of NZ-NO was clarified by ESI+/MS. In silico toxicology study confirmed the mutagenicity and toxicity of NZ-NO. Experiments evidenced that ascorbic acid strongly suppresses the nitrosation of NZ suggesting their co-administration for protection from potential risks. In addition, the impacts of the HILIC method on safety, health, and environment were favorably evaluated by three green analytical chemistry metrics and it was proved that, unlike the popular impression, HILIC methods could be green to the environment. Copyright (C) 2019, Food and Drug Administration, Taiwan. Published by Elsevier Taiwan LLC.