Calvatianone, a Sterol Possessing a 6/5/6/5-Fused Ring System with a Contracted Tetrahydrofuran B-Ring, from the Fruiting Bodies of Calvatia nipponica

Naturally Occurring Norsteroids and Their Design and Pharmaceutical Application

The main focus of this review is to introduce readers to the fascinating class of lipid molecules known as norsteroids, exploring their distribution across various biotopes and their biological activities. The review provides an in-depth analysis of various modified steroids, including A, B, C, and D-norsteroids, each characterized by distinct structural alterations. These modifications, which range from the removal of specific methyl groups to changes in the steroid core, result in unique molecular architectures that significantly impact their biological activity and therapeutic potential. The discussion on A, B, C, and D-norsteroids sheds light on their unique configurations and how these structural modifications influence their pharmacological properties. The review also presents examples from natural sources that produce a diverse array of steroids with distinct structures, including the aforementioned A, B, C, and D-nor variants. These compounds are sourced from marine organisms like sponges, soft corals, and starfish, as well as terrestrial entities such as plants, fungi, and bacteria. The exploration of these steroids encompasses their biosynthesis, ecological significance, and potential medical applications, highlighting a crucial area of interest in pharmacology and natural product chemistry. The review emphasizes the importance of researching these steroids for drug development, particularly in addressing diseases where conventional medications are inadequate or for conditions lacking sufficient therapeutic options. Examples of norsteroid synthesis are provided to illustrate the practical applications of this research.

Biological Activities of Secondary Metabolites from the Edible-Medicinal Macrofungi

Macrofungi are well-known as edible-medicinal mushrooms, which belong mostly to Basidiomycota, with a few from Ascomycota. In recent years, macrofungi have been recognized as a rich resource of structurally unique secondary metabolites, demonstrating a wide range of bioactivities, including anti-tumor, antioxidant, anti-inflammatory, antimicrobial, antimalarial, neuro-protective, hypoglycemic, and hypolipidemic activities. This review highlights over 270 natural products produced by 17 families of macrofungi covering 2017 to 2023, including their structures, bioactivities, and related molecular mechanisms.

DeepSAT: Learning Molecular Structures from Nuclear Magnetic Resonance Data

The identification of molecular structure is essential for understanding chemical diversity and for developing drug leads from small molecules. Nevertheless, the structure elucidation of small molecules by Nuclear Magnetic Resonance (NMR) experiments is often a long and non-trivial process that relies on years of training. To achieve this process efficiently, several spectral databases have been established to retrieve reference NMR spectra. However, the number of reference NMR spectra available is limited and has mostly facilitated annotation of commercially available derivatives. Here, we introduce DeepSAT, a neural network-based structure annotation and scaffold prediction system that directly extracts the chemical features associated with molecular structures from their NMR spectra. Using only the 1H-13C HSQC spectrum, DeepSAT identifies related known compounds and thus efficiently assists in the identification of molecular structures. DeepSAT is expected to accelerate chemical and biomedical research by accelerating the identification of molecular structures.

N,N-Dimethyl-anthranilic Acid from Calvatia nipponica Mushroom Fruiting Bodies Induces Apoptotic Effects on MDA-MB-231 Human Breast Cancer Cells

Breast cancer ranks among the most prevalent malignancies affecting women worldwide, and apoptosis-targeting drugs are attractive candidates for the treatment of cancer. In the current study, we investigated the in vitro cytotoxicity of the mushroom Calvatia nipponica in human breast cancer cells (MDA-MB-231), identified potential antitumor compounds through bioactivity-guided isolation, and elucidated the antitumor, pro-apoptotic molecular mechanisms of the identified bioactive compounds. C. nipponica is edible when young, and it has been used as a food source as well as a traditional medicine in wound dressings. However, only a limited number of studies have reported its chemical composition and biological activities. In the screening test, the methanol extract of C. nipponica fruiting bodies exhibited cytotoxicity against MDA-MB-231 cells. Bioactivity-guided fractionation of the methanol (MeOH) extract and chemical investigation of the active fractions resulted in the isolation of fourteen compounds (1-14), including six alkaloids (1-3, 5, 7, and 8), two phenolic compounds (4 and 6), one fatty acid (9), and five steroids (10-14). The structures of the isolated compounds were determined using NMR spectroscopic methods, liquid chromatography-mass spectrometry, and comparison of data with previously reported values. The isolated compounds (1-14) were tested for cytotoxicity against MDA-MB-231 cells, where compound 1, i.e., N,N-dimethyl-anthranilic acid, exhibited the most significant cytotoxicity against MDA-MB-231 cells, with an IC₅₀ value of 90.28 ± 4.23 μM and apoptotic cell death of 56.01% ± 2.64% at 100 μM. Treatment with compound 1 resulted in an upregulation of protein levels, including cleaved caspase-8, cleaved poly (ADP-ribose) polymerase, Bcl-2-associated X protein (Bax), cleaved caspase-3, cleaved caspase-9, Bad, and Cytochrome c, but decreased the levels of B-cell lymphoma 2 (Bcl-2). Overall, these results indicate that N,N-dimethyl-anthranilic acid (1) may have anti-breast cancer activity and is probably involved in the induction of apoptosis mediated by extrinsic and intrinsic signaling pathways.

Estrogenic Activity of 4-Hydroxy-Benzoic Acid from Acer tegmentosum via Estrogen Receptor α-Dependent Signaling Pathways

Acer tegmentosum, a deciduous tree belonging to Aceraceae, has been used in traditional oriental medicine for treating hepatic disorders, such as hepatitis, cirrhosis, and liver cancer. We evaluated the estrogen-like effects of A. tegmentosum using an estrogen receptor (ER)-positive breast cancer cell line, namely MCF-7, to identify potential phytoestrogens and found that an aqueous extract of A. tegmentosum promoted cell proliferation in MCF-7 cells. Five phenolic compounds (1-5) were separated and identified from the active fraction using bioassay-guided fractionation of crude A. tegmentosum extract and phytochemical analysis. The chemical structures of the compounds were characterized as vanillic acid (1), 4-hydroxy-benzoic acid (2), syringic acid (3), isoscopoletin (4), and (E)-ferulic acid (5) based on the analysis of their nuclear magnetic resonance spectra and liquid chromatography-mass spectrometry data. All five compounds were evaluated using an E-screen assay for their estrogen-like effects on MCF-7 cells. Among the tested compounds, only 4-hydroxy-benzoic acid (2) promoted the proliferation of MCF-7 cells, which was mitigated by the ER antagonist, ICI 182,780. The mechanism underlying the estrogen-like effect of 4-hydroxy-benzoic acid (2) was evaluated via western blotting analysis to determine the expression levels of extracellular signal-regulated kinase (ERK), phosphoinositide 3-kinase (PI3K), serine/threonine kinase (AKT), and ERα. Our results demonstrated that 4-hydroxy-benzoic acid (2) induced the increase in the protein expression levels of p-ERK, p-AKT, p-PI3K, and p-Erα, concentration dependently. Collectively, these experimental results suggest that 4-hydroxy-benzoic acid (2) is responsible for the estrogen-like effects of A. tegmentosum and may potentially aid in the control of estrogenic effects during menopause.

Meyeroguilline E, a New Isoindolinone Alkaloid from the Poisonous Mushroom Chlorophyllum molybdites, and Identification of Compounds with Multidrug Resistance (MDR) Reversal Activities

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.

A New Labdane-Type Diterpene, 6-O-Acetyl-(12R)-epiblumdane, from Stevia rebaudiana Leaves with Insulin Secretion Effect

Stevia rebaudiana (Asteraceae), commonly known as candyleaf, sweetleaf, or sugarleaf, is a branched bushy shrub whose leaves are used as a natural sweetener owing to the high content of sweet diterpenes. As part of our ongoing work to identify structurally novel and bioactive natural products, phytochemical investigation of the ethanolic extract of S. rebaudiana leaves led to the isolation of one new labdane-type diterpene, 6-O-acetyl-(12R)-epiblumdane (1), and nine known terpenoids, including six diterpenes (2–6 and 10), two monoterpenes (7 and 8), and one triterpene (9). The structure of the new compound 1 was elucidated via analysis of one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopic data and high-resolution electrospray ionization mass spectrometry data, and its absolute configuration was established using electronic circular dichroism (ECD) calculations and gauge-including atomic orbital NMR chemical shift calculations, followed by DP4 + probability analysis. The isolated compounds 1–10 were evaluated for their effects on glucose-stimulated insulin secretion in the INS-1 rat pancreatic β-cell line. The new compound 1, 6-O-acetyl-(12R)-epiblumdane, stimulated glucose-stimulated insulin secretion in INS-1 pancreatic β-cells without inducing cytotoxicity. Thus, 6-O-acetyl-(12R)-epiblumdane (1), an active compound derived from S. rebaudiana leaves, can be used as a potential therapeutic agent to prevent type 2 diabetes.

Structure and Biological Activity of Ergostane-Type Steroids from Fungi

Mushrooms are known not only for their taste but also for beneficial effects on health attributed to plethora of constituents. All mushrooms belong to the kingdom of fungi, which also includes yeasts and molds. Each year, hundreds of new metabolites of the main fungal sterol, ergosterol, are isolated from fungal sources. As a rule, further testing is carried out for their biological effects, and many of the isolated compounds exhibit one or another activity. This study aims to review recent literature (mainly over the past 10 years, selected older works are discussed for consistency purposes) on the structures and bioactivities of fungal metabolites of ergosterol. The review is not exhaustive in its coverage of structures found in fungi. Rather, it focuses solely on discussing compounds that have shown some biological activity with potential pharmacological utility.

Identification of Antibacterial Sterols from Korean Wild Mushroom Daedaleopsis confragosa via Bioactivity- and LC-MS/MS Profile-Guided Fractionation

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.

Two New Fatty Acid Derivatives, Omphalotols A and B and Anti-Helicobacterpylori Fatty Acid Derivatives from Poisonous Mushroom Omphalotus japonicus

As part of ongoing systematic research into the discovery of bioactive secondary metabolites with novel structures from Korean wild mushrooms, we investigated secondary metabolites from a poisonous mushroom, Omphalotus japonicus (Kawam.) Kirchm. & O. K. Mill. belonging to the family Marasmiaceae, which causes nausea and vomiting after consumption. The methanolic extract of O. japonicus fruiting bodies was subjected to the fractionation by solvent partition, and the CH₂Cl₂ fraction was analyzed for the isolation of bioactive compounds, aided by an untargeted liquid chromatography mass spectrometry (LC–MS)-based analysis. Through chemical analysis, five fatty acid derivatives (1–5), including two new fatty acid derivatives, omphalotols A and B (1 and 2), were isolated from the CH₂Cl₂ fraction, and the chemical structures of the new compounds were determined using 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and high resolution electrospray ionization mass spectrometry (HR-ESIMS), as well as fragmentation patterns in MS/MS data and chemical reactions followed by the application of Snatzke’s method and competing enantioselective acylation (CEA). In the anti-Helicobacter pylori activity test, compound 1 showed moderate antibacterial activity against H. pylori strain 51 with 27.4% inhibition, comparable to that of quercetin as a positive control. Specifically, compound 3 exhibited the most significant antibacterial activity against H. pylori strain 51, with MIC₅₀ and MIC₉₀ values of 9 and 20 μM, respectively, which is stronger inhibitory activity than that of another positive control, metronidazole (MIC₅₀ = 17 μM and MIC₉₀ = 46 μM). These findings suggested the experimental evidence that the compound 3, an α,β-unsaturated ketone derivative, could be used as a moiety in the development of novel antibiotics against H. pylori.

Estrogenic Activity of Mycoestrogen (3β,5α,22E)-Ergost-22-en-3-ol via Estrogen Receptor α-Dependent Signaling Pathways in MCF-7 Cells

Armillariella tabescens (Scop.) Sing., a mushroom of the family Tricholomataceae, has been used in traditional oriental medicine to treat cholecystitis, improve bile secretion, and regulate bile-duct pressure. The present study evaluated the estrogen-like effects of A. tabescens using a cell-proliferation assay in an estrogen-receptor-positive breast cancer cell line (MCF-7). We found that the methanol extract of A. tabescens fruiting bodies promoted cell proliferation in MCF-7 cells. Using bioassay-guided fractionation of the methanol extract and chemical investigation, we isolated and identified four steroids and four fatty acids from the active fraction. All eight compounds were evaluated by E-screen assay for their estrogen-like effects in MCF-7 cells. Among the tested isolates, only (3β,5α,22E)-ergost-22-en-3-ol promoted cell proliferation in MCF-7 cells; this effect was mitigated by the ER antagonist, ICI 182,780. The mechanism underlying the estrogen-like effect of (3β,5α,22E)-ergost-22-en-3-ol was evaluated using Western blot analysis to detect the expression of extracellular signal-regulated kinase (ERK), phosphatidylinositol 3-kinase (PI3K), Akt, and estrogen receptor α (ERα). We found that (3β,5α,22E)-ergost-22-en-3-ol induced an increase in phosphorylation of ERK, PI3K, Akt, and ERα. Together, these experimental results suggest that (3β,5α,22E)-ergost-22-en-3-ol is responsible for the estrogen-like effects of A. tabescens and may potentially aid control of estrogenic activity in menopause.

Survey of natural products reported by Asian research groups in 2020

The new natural products reported in 2020 in peer-reviewed articles in journals with good reputations were reviewed and analyzed. The advances made by Asian research groups in the field of natural products chemistry in 2020 were summarized. Compounds with unique structural features and/or promising bioactivities originating from Asian natural sources were discussed based on their structural classification.

Identification of Renoprotective Phytosterols from Mulberry (Morus alba) Fruit against Cisplatin-Induced Cytotoxicity in LLC-PK1 Kidney Cells

The aim of this study was to explore the protective effects of bioactive compounds from the fruit of the mulberry tree (Morus alba L.) against cisplatin-induced apoptosis in LLC-PK1 pig kidney epithelial cells. Morus alba fruit is a well-known edible fruit commonly used in traditional folk medicine. Chemical investigation of M. alba fruit resulted in the isolation and identification of six phytosterols (1-6). Their structures were determined as 7-ketositosterol (1), stigmast-4-en-3β-ol-6-one (2), (3β,6α)-stigmast-4-ene-3,6-diol (3), stigmast-4-ene-3β,6β-diol (4), 7β-hydroxysitosterol 3-O-β-d-glucoside (5), and 7α-hydroxysitosterol 3-O-β-d-glucoside (6) by analyzing their physical and spectroscopic data as well as liquid chromatography/mass spectrometry data. All compounds displayed protective effects against cisplatin-induced LLC-PK1 cell damage, improving cisplatin-induced cytotoxicity to more than 80% of the control value. Compound 1 displayed the best effect at a relatively low concentration by inhibiting the percentage of apoptotic cells following cisplatin treatment. Its molecular mechanisms were identified using Western blot assays. Treatment of LLC-PK1 cells with compound 1 decreased the upregulated phosphorylation of p38 and c-Jun N-terminal kinase (JNK) following cisplatin treatment. In addition, compound 1 significantly suppressed cleaved caspase-3 in cisplatin-induced LLC-PK1 cells. Taken together, these findings indicated that cisplatin-induced apoptosis was significantly inhibited by compound 1 in LLC-PK1 cells, thereby supporting the potential of 7-ketositosterol (1) as an adjuvant candidate for treating cisplatin-induced nephrotoxicity.

Phytochemical Investigation of Bioactive Compounds from White Kidney Beans (Fruits of Phaseolus multiflorus var. Albus): Identification of Denatonium with Osteogenesis-Inducing Effect

Phaseolus multiflorus var. albus (Leguminosae), commonly known as “white kidney bean”, is a twining perennial vine whose fruit has been used as a popular food worldwide owing to its high nutritional content, in terms of proteins, carbohydrates, fats, and vitamins. As part of our ongoing study to investigate novel bioactive components from various natural resources, a phytochemical investigation of the extract of P. multiflorus var. albus fruits resulted in the isolation of three phenolic compounds (1–3) and one dipeptide (4). The chemical structures of the compounds (1–4) were determined through 1D and 2D nuclear magnetic resonance spectroscopy and high-resolution-liquid chromatography–mass spectrometry; they were identified as denatonium (1), trans-ferulic acid ethyl ester (2), eugenin (3), and α-L-glutamyl-L-Leucine (4). Intriguingly, denatonium (1) is known to be the most bitter chemical compound. To the best of our knowledge, denatonium (1) was identified from natural sources for the first time, and compounds 2–4 were reported for the first time from P. multiflorus var. albus in this study; however, compound 2 turned out to be an artifact produced by an extraction with ethanol. The isolated compounds 1–4 were tested for their regulatory effects on the differentiation between osteogenesis and adipogenesis of mesenchymal stem cells (MSCs). Compound 4 slightly suppressed the adipogenic differentiation of MSCs, and compounds 1 and 4 stimulated osteogenic differentiation, unlike the negative control. These findings provide experimental evidence that compounds 1 and 4 may induce the osteogenesis of MSCs and activate bone formation.

Ginkgonitroside, a new nitrophenyl glycoside and bioactive compounds from Ginkgo biloba leaves controlling adipocyte and osteoblast differentiation

Eight compounds (1-8) including one novel nitrophenyl glycoside, ginkgonitroside (1) were isolated from the leaves of Ginkgo biloba, a popular medicinal plant. The structure of the new compound was characterized using extensive spectroscopic analyses via 1D and 2D NMR data interpretations, HR-ESIMS, and chemical transformation. To the best of our knowledge, the present study is the first to report the presence of nitrophenyl glycosides, which are relatively unique phytochemicals in natural products, in G. biloba. The isolated compounds (1-8) were examined for their effects on the regulation of mesenchymal stem cell (MSC) differentiation. Compounds 1-3 and 8 were able to suppress MSC differentiation toward adipocytes. In contrast, compounds 5 and 8 showed activity promoting osteogenic differentiation of MSCs. These findings demonstrate that the active compounds showed regulatory activity on MSC differentiation between adipocytes and osteocytes.

Pulveraven A from the fruiting bodies of Pulveroboletus ravenelii induces apoptosis in breast cancer cell via extrinsic apoptotic signaling pathway

Pulveroboletus ravenelii (Beck. et Curt.) Murr. (Boletaceae), commonly known as Ravenel's bolete, is an edible and medicinal mushroom, and is also used for preparing mushroom-based dyes. As part of a continuing project to discover the bioactive natural products from wild mushrooms, we analyzed the methanol (MeOH) extract of P. ravenelii to identify metabolites with the anticancer activity. Chemical analysis of the MeOH extract combined with liquid chromatography-mass spectrometry (LC-MS) analysis led to the isolation of a phenolic compound, pulveraven A (PA), whose chemical structure was determined using a combination of 1D and 2D NMR and LC-MS analysis. In the present study, we investigated the cytotoxicity and anticancer mechanisms of pulveraven A using human breast cancer (MCF-7) cells, and demonstrated that it reduced cell viability of MCF-7 cells below 50% (71.74 ± 3.61 μM). Annexin V Alexa Fluor 488 binding assay and western blot results revealed that pulveraven A induced apoptotic cell death via the extrinsic apoptosis pathway, as indicated by the activation of initiator caspase-8 and executioner caspase-7. Furthermore, it was accompanied by an increase in the Bax/Bcl-2 ratio. These results suggest that pulveraven A induces apoptosis in breast cancer cells via the extrinsic apoptotic signaling pathway.

Bioactive Phytochemicals from Mulberry: Potential Anti-Inflammatory Effects in Lipopolysaccharide-Stimulated RAW 264.7 Macrophages

The fruits of the mulberry tree (Morus alba L.), known as white mulberry, have been consumed in various forms, including tea, beverages, and desserts, worldwide. As part of an ongoing study to discover bioactive compounds from M. alba fruits, the anti-inflammatory effect of compounds from M. alba were evaluated in lipopolysaccharide (LPS)-stimulated mouse RAW 264.7 macrophages. Phytochemical analysis of the ethanol extract of the M. alba fruits led to the isolation of 22 compounds. Among the isolated compounds, to the best of our knowledge, compounds 1, 3, 5, 7, 11, 12, and 14-22 were identified from M. alba fruits for the first time in this study. Inhibitory effects of 22 compounds on the production of the nitric oxide (NO) known as a proinflammatory mediator in LPS-stimulated RAW 264.7 macrophages were evaluated using NO assays. Western blot analysis was performed to evaluate the anti-inflammatory effects of cyclo(L-Pro-L-Val) (5). We evaluated whether the anti-inflammatory effects of cyclo(L-Pro-L-Val) (5) following LPS stimulation in RAW 264.7 macrophages occurred because of phosphorylation of IκB kinase alpha (IKKα), IκB kinase beta (IKKβ), inhibitor of kappa B alpha (IκBα), nuclear factor kappa B (NF-κB) and activations of inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). Cyclo(L-Pro-L-Val) (5) significantly suppressed phosphorylations of IKKα, IKKβ, IκBα, and NF-κB and activations of iNOS and COX-2 in a concentration-dependent manner. Taken together, these results indicate that cyclo(L-Pro-L-Val) (5) can be considered a potential therapeutic agent for the treatment of inflammation-associated disorders.

A critical review on the use of DP4+ in the structural elucidation of natural products: the good, the bad and the ugly. A practical guide

Covering: 2015 up to the end of 2020Even in the golden age of NMR, the number of natural products being incorrectly assigned is becoming larger every day. The use of quantum NMR calculations coupled with sophisticated data analysis provides ideal complementary tools to facilitate the elucidation process in challenging cases. Among the current computational methodologies to perform this task, the DP4+ probability is a popular and widely used method. This updated version of Goodman's DP4 synergistically combines NMR calculations at higher levels of theory with the Bayesian analysis of both scaled and unscaled data. Since its publication in late 2015, the use of DP4+ to solve controversial natural products has substantially grown, with several predictions being confirmed by total synthesis. To date, the structures of more than 200 natural products were determined with the aid of DP4+. However, all that glitters is not gold. Besides its intrinsic limitations, on many occasions it has been improperly used with potentially important consequences on the quality of the assignment. Herein we present a critical revision on how the scientific community has been using DP4+, exploring the strengths of the method and how to obtain optimal results from it. We also analyze the weaknesses of DP4+, and the paths to by-pass them to maximize the confidence in the structural elucidation.

Identification of bioactive compounds from mulberry enhancing glucose-stimulated insulin secretion

Previously, we isolated six heterocyclic compounds (1-6) from the fruits of mulberry trees (Morus alba L.) and determined that loliolide affords rat pancreatic islet β-cell (INS-1) protection against streptozotocin‑induced cytotoxicity. In the present study, we further investigated the effect of the six heterocyclic compounds (1-6) on glucose-stimulated insulin secretion (GSIS) in INS-1 cells. Among them, (R)‑5‑hydroxypyrrolidin‑2‑one(1) and indole (6) increased GSIS without inducing cytotoxicity. Additionally, compounds 1 and 6 enhanced the phosphorylation of total insulin receptor substrate-2, phosphatidylinositol 3-kinase, and Akt, and activated pancreatic and duodenal homeobox-1, which play a crucial role in β-cell functions related to insulin secretion. Collectively, these findings indicate that (R)‑5‑hydroxypyrrolidin‑2‑one(1) and indole (6), isolated from M. alba fruits, may be beneficial in managing type 2 diabetes.

Ginkwanghols A and B, osteogenic coumaric acid-aliphatic alcohol hybrids from the leaves of Ginkgo biloba

Ginkgo biloba (Ginkgoaceae), commonly known as "ginkgo", is called a living fossil, and it has been cultivated early in human history for various uses in traditional medicine and as a source of food. As part of ongoing research to explore the chemical diversity and biologically active compounds from natural resources, two new coumaric acid-aliphatic alcohol hybrids, ginkwanghols A (1) and B (2) were isolated from the leaves of G. biloba. The coumaric acid-aliphatic alcohol hybrids of natural products have rarely been reported. The structures of the new compounds were determined by extensive NMR spectroscopic analysis, HRESI-MS, and quantum chemical ECD calculations, and by comparing the experimental HRESI-MS/MS spectrum of chemically transformed compound 1a with the predicted HRESI-MS/MS spectra proposed from CFM-ID 3.0, a software tool for MS/MS spectral prediction and MS-based compound identification. Ginkwanghols A (1) and B (2) increased alkaline phosphatase (ALP) production in C3H10T1/2, a mouse mesenchymal stem cell line, in a dose-dependent manner. In addition, ginkwanghols A and B mediated the promotion of osteogenic differentiation as indicated by the induction of the mRNA expression of the osteogenic markers ALP and osteopontin (OPN).

Phytochemical Analysis of the Fruits of Sea Buckthorn (Hippophae rhamnoides): Identification of Organic Acid Derivatives

Hippophae rhamnoides L. (Elaeagnaceae), commonly known as “Sea buckthorn” and “Vitamin tree”, is a spiny deciduous shrub whose fruit is known for its nutritional composition, such as vitamin C, and is consumed as a dietary supplement worldwide. As part of our ongoing efforts to identify structurally new and bioactive constituents from natural resources, the phytochemical investigation of the extract of H. rhamnoides fruits led to the isolation of one malate derivative (1), five citrate derivatives (2–6), and one quinate derivative (7). The structures of the isolated compounds were elucidated by analysis of 1D and 2D nuclear magnetic resonance (NMR) spectroscopic data and high-resolution electrospray ionization (HR-ESI) liquid chromatography–mass spectrometry (LC/MS) data. Three of the citrate derivatives were identified as new compounds: (S)-1-butyl-5-methyl citrate (3), (S)-1-butyl-1′-methyl citrate (4), and (S)-1-methyl-1′-butyl citrate (6), which turned out to be isolation artifacts. The absolute configurations of the new compounds were established by quantum chemical electronic circular dichroism (ECD) calculation, which is an informative tool for verifying the absolute configuration of organic acid derivatives. The isolated compounds 1–7 were evaluated for their stimulatory effects on osteogenesis. Compounds 1, 3, 4, 6, and 7 stimulated osteogenic differentiation up to 1.4 fold, compared to the negative control. These findings provide experimental evidence that active compounds 1, 3, 4, 6, and 7 induce the osteogenesis of mesenchymal stem cells and activate bone formation.

Antidiabetic Flavonoids from Fruits of Morus alba Promoting Insulin-Stimulated Glucose Uptake via Akt and AMP-Activated Protein Kinase Activation in 3T3-L1 Adipocytes

Morus alba (Moraceae), known as white mulberry, has been used to treat fever, protect against liver damage, improve eyesight, and lower blood sugar levels in traditional oriental medicine. Few studies have been conducted on the antidiabetic compounds identified from M. alba and their underlying mechanisms of action. Consequently, in this study, the fruits of M. alba were investigated for potential antidiabetic natural products using 3T3-L1 adipocytes. Phytochemical analysis of the ethanolic extract of M. alba fruits, followed by high-performance liquid chromatography (HPLC), purification led to the isolation of two main compounds: rutin and quercetin-3-O-β-d-glucoside (Q3G). Long-term use of available drugs for treating type 2 diabetes ((T2D) is often accompanied by undesirable side effects, which have generated increased interest in the development of more effective and safer antidiabetic agents. Examination of the isolated compounds, rutin and Q3G, for antidiabetic or anti-obesity properties or both in 3T3-L1 adipocytes demonstrated that they both improved glucose uptake via Akt-mediated insulin signaling pathway or AMP-activated protein kinase (AMPK) activation in 3T3-L1 adipocytes. The compounds also showed a positive effect on lipid accumulation in adipocytes, suggesting that glucose uptake occurred through activation of the Akt and AMPK signaling pathway without inducing adipogenesis. Taken together, our findings suggest that rutin and Q3G in M. alba fruits have the potential to induce fewer side effects such as weight gain, and these active compounds could be potential therapeutic candidates for the management of T2D.

Anti-fibrotic effects of brevilin A in hepatic fibrosis via inhibiting the STAT3 signaling pathway

Hepatic fibrosis is a chronic liver disease characterized by the accumulation of extracellular matrix (ECM). Activation of hepatic stellate cells (HSCs) after repetitive liver damage is a key event in hepatic fibrogenesis. As part of ongoing research projects to identify pharmacologically effective natural products, the phytochemical investigation of a MeOH extract of Centipeda minima led to the isolation of a sesquiterpene lactone, brevilin A, which was explored to elucidate potential anti-fibrotic effects by reversing HSC activation. First, we observed that transforming growth factor (TGF)-β1 treatment significantly increased the expression levels of HSC activation marker, α-smooth muscle actin (α-SMA), and ECM protein such as collagen and fibronectin. Then, we demonstrated that brevilin A reversed the TGF-β1-induced increase in protein and mRNA expression levels of α-SMA and collagen. To investigate the underlying molecular mechanism of brevilin A, we evaluated the effects of brevilin A on the STAT3 signaling pathway. STAT3 phosphorylation, increased by TGF-β1 treatment, was strongly inhibited by brevilin A; the expression levels of fibronectin and connective tissue growth factor were also significantly decreased by brevilin A. The present study indicated that brevilin A has a preventive and therapeutic potential against hepatic fibrosis.

Identification of Bioactive Natural Product from the Stems and Stem Barks of Cornus walteri: Benzyl Salicylate Shows Potential Anti-Inflammatory Activity in Lipopolysaccharide-Stimulated RAW 264.7 Macrophages

Cornus walteri (Cornaceae), known as Walter's dogwood, has been used to treat dermatologic inflammation and diarrheal disease in traditional oriental medicine. As part of an ongoing research project to discover natural products with biological activities, the anti-inflammatory potential of compounds from C. walteri in lipopolysaccharide (LPS)-stimulated mouse RAW 264.7 macrophages were explored. Phytochemical analysis of the methanol extract of the stem and stem bark of C. walteri led to the isolation of 15 chemical constituents. These compounds were evaluated for their inhibitory effects on the production of the proinflammatory mediator nitric oxide (NO) in LPS-stimulated macrophages, as measured by NO assays. The molecular mechanisms underlying the anti-inflammatory activity were investigated using western blotting. Our results demonstrated that among 15 chemical constituents, lupeol and benzyl salicylate inhibited NO production in LPS-activated RAW 264.7 macrophages. Benzyl salicylate was more efficient than NG-monomethyl-L-arginine mono-acetate salt (L-NMMA) in terms of its inhibitory effect. In addition, the mechanism of action of benzyl salicylate consisted of the inhibition of phosphorylation of IκB kinase alpha (IKKα), IκB kinase beta (IKKβ), inhibitor of kappa B alpha (IκBα), and nuclear factor kappa B (NF-κB) in LPS-stimulated macrophages. Furthermore, benzyl salicylate inhibited the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Taken together, these results suggest that benzyl salicylate present in the stem and stem bark of C. walteri has potential anti-inflammatory activity, supporting the potential application of this compound in the treatment of inflammatory diseases.

Ulmusakidian, a new coumarin glycoside and antifungal phenolic compounds from the root bark of Ulmus davidiana var. japonica

Bioactivity-driven LC/MS-based phytochemical analysis of the root bark extract of Ulmus davidiana var. japonica led to the isolation of 10 compounds including a new coumarin glycoside derivative, ulmusakidian (1). The structure of the new compound was elucidated using extensive spectroscopic analyses via 1D and 2D NMR spectroscopic data interpretations, HR-ESIMS, and chemical transformation. The isolated compounds 1-10 were tested for their antifungal activity against human fungal pathogens Cryptococcus neoformans and Candida albicans. Compounds 9 and 10 showed antifungal activity against C. neoformans, with the lowest minimal inhibitory concentration (MIC) of 12.5-25.0 µg/mL, whereas none of the compounds showed antifungal activity against C. albicans.

Phloridzin Acts as an Inhibitor of Protein-Tyrosine Phosphatase MEG2 Relevant to Insulin Resistance

Inhibition of the megakaryocyte protein tyrosine phosphatase 2 (PTP-MEG2, also named PTPN9) activity has been shown to be a potential therapeutic strategy for the treatment of type 2 diabetes. Previously, we reported that PTP-MEG2 knockdown enhances adenosine monophosphate activated protein kinase (AMPK) phosphorylation, suggesting that PTP-MEG2 may be a potential antidiabetic target. In this study, we found that phloridzin, isolated from Ulmus davidiana var. japonica, inhibits the catalytic activity of PTP-MEG2 (half-inhibitory concentration, IC₅₀ = 32 ± 1.06 μM) in vitro, indicating that it could be a potential antidiabetic drug candidate. Importantly, phloridzin stimulated glucose uptake by differentiated 3T3-L1 adipocytes and C2C12 muscle cells compared to that by the control cells. Moreover, phloridzin led to the enhanced phosphorylation of AMPK and Akt relevant to increased insulin sensitivity. Importantly, phloridzin attenuated palmitate-induced insulin resistance in C2C12 muscle cells. We also found that phloridzin did not accelerate adipocyte differentiation, suggesting that phloridzin improves insulin sensitivity without significant lipid accumulation. Taken together, our results demonstrate that phloridzin, an inhibitor of PTP-MEG2, stimulates glucose uptake through the activation of both AMPK and Akt signaling pathways. These results strongly suggest that phloridzin could be used as a potential therapeutic candidate for the treatment of type 2 diabetes.

Anti-Adipogenic Polyacetylene Glycosides from the Florets of Safflower (Carthamus tinctorius)

Safflower (Carthamus tinctorius) is an annual herb belonging to the Compositae family; it has a history of use as a food colorant, dye, and medicine in oriental countries. LC-MS-UV-based chemical analysis of extract of the florets of C. tinctorius led to the isolation of two new C₁₀-polyacetylene glycosides, (8Z)-decaene-4,6-diyne-1,10-diol-1-O-β-d-glucopyranoside (1) and (8S)-deca-4,6-diyne-1,8-diol-1-O-β-d-glucopyranoside (2), together with five known analogs (3–7). The structures of the new compounds were determined by using 1D and 2D NMR spectroscopic data and HR-MS data, as well as chemical transformations. Of compounds 1–7, compounds 2, 3, and 4 inhibited the adipogenesis of 3T3-L1 preadipocytes, whereas compounds 1 and 6 promoted adipogenesis. Compounds 2, 3, and 4 also prevented lipid accumulation through the suppression of the expression of lipogenic genes and the increase of the expression of lipolytic genes. Moreover, compounds 3 and 4 activated AMPK, which is known to facilitate lipid metabolism. Our findings provide a mechanistic rationale for the use of safflower-derived polyacetylene glycosides as potential therapeutic agents against obesity.