Electronic Circular Dichroism Calculations Research Articles

Cycloartane-type triterpenoids from Combretum quadrangulare Kurz with PCSK9 secretion inhibitory activities.

Nine previously undescribed (1-9) and seven known (10-16) cycloartane-type triterpenoids were isolated and characterized from Combretum quadrangulare Kurz using physicochemical and spectroscopic methods. The absolute configurations of these compounds were determined through modified Mosher's method and quantum chemical calculation of electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectra. Their inhibitory activities against PCSK9 secretion were assessed, and a plausible structure-activity relationship was delineated. Compounds 2, 14, and 15 exhibited notable inhibitory effects on PCSK9 mRNA and protein levels, and significant PCSK9 mRNA inhibition was observed when co-treated with atorvastatin. Compound 15 showed the most potent activity, markedly enhancing LDL uptake compared to the negative control. In vivo pharmacokinetic studies confirmed that compound 15 exhibited higher distribution in the liver than plasma, where PCSK9 is predominantly synthesized. These findings emphasize the potential significance of the cycloartane-type triterpenoid scaffold in discovering PCSK9 inhibitors.

A Novel Lactam and Two Rare Mycophenolic Acid Derivatives from the Fungus Penicillium Sclerotiorum JBHL321.

A novel lactam penicillactam (1), two rare mycophenolic acid (MPA) derivatives penimycophens A and B (2 and 3), together with two known biogenetically related MPA derivatives (4 and 5) and a known alkaloid (6) were isolated from the Penicillium sclerotiorum JBHL321. The structures of these compounds were determined by comprehensive spectroscopic analyses. The absolute configuration of 1 was confirmed by electronic circular dichroism (ECD) calculations. Compound 1 represent the rare example of a oxygen bridge-linked lactam from natural products. Structurally, compounds 2 and 3 were rare MPA derivatives featuring a methoxy group at C-3. The inhibitory activity of compounds 1-6 against two phytopathogenic fungi, three phytopathogenic bacteria and four cancer cell lines were evaluated. Compounds 2-5 exhibited significant cytotoxic activity against HeLa, MCF-7, A549 and MGC-803 cells with IC50 values in the low micromolar to nanomolar. Compound 3 exhibited especially cytotoxic activity against four different cell lines with IC50 values ranging from 0.06-0.14 μM, compared to IC50 values ranging from 0.62-2.51 μM for epirubicin.

Identification of New Compounds from the Roots of Rubia tibetica Hook. f.

Rubia tibetica Hook. f is a traditional Tibetan medicinal plant, with its roots serving as the primary medicinal part. Two new compounds, Rubiaxylm C and E (1 and 3), and one new natural compound, Rubiaxylm D (2) were isolated from R. tibetica, along with five known compounds (4-8). The structures of the previously undescribed compounds were elucidated by HR-ESIMS, 1D/2D NMR spectroscopic data and electronic circular dichroism calculations. Compound 1 is a rare anthrone substituted with a carbonyl group at position 1. Furthermore, all isolated compounds were tested for their cytotoxicity against HepG2 cell lines.

Structurally Diverse Duclauxins from a Coral-Derived Talaromyces sp. and Insight into Determining the Configuration at C-1 of Heptacyclic Duclauxins by 1H NMR.

A chemical investigation of the coral-derived fungus Talaromyces sp. TJ403-AL05 led to the isolation of 18 duclauxin analogues (1-18), 14 of which, taladuxins A-N (1-14), are new and consist of the first example of duclauxin fused with one 1,6-dioxaspiro[4.5]decan-2-one moiety (1), as well as its biosynthetic product (2), and 12 6/6/6/5/6/6/6 heptacyclic derivatives (3-14). Comprehensive spectroscopic analyses, electronic circular dichroism (ECD) calculations, DP4+ probability analyses, single-crystal X-ray diffraction, and vibrational circular dichroism (VCD) calculations were employed to characterize their structures and revise the published structure of verruculosin B. An efficient 1H NMR method was established to discriminate 1R and 1S configurations at C-1 of 6/6/6/5/6/6/6 heptacyclic duclauxins according to chemical shift differences of diastereotopic methylene H2-11 or H2-12 (ΔδH-11 or ΔδH-12). Compounds 4, 7-8, 13-15, and 18 exhibited moderate inhibition of Arabidopsis thaliana 4-hydroxyphenylpyruvate dioxygenase (AtHPPD), with IC50 values ranging from 17.1 to 71.3 μM.

Multioxidized polyketides from an endophytic Penicillium sp. YUD17006 associated with Gastrodia elata

Three novel, highly oxygenated polyketides, multioketides A−C (1−3), and three previously described multioxidized aromatic polyketides (4−6), were isolated from an endophytic Penicillium sp. YUD17006 associated with Gastrodia elata. Their chemical structures were elucidated using extensive spectroscopic data, electronic circular dichroism calculations, and single X-ray diffraction analysis. All metabolites were characterized by a typical α,β-unsaturated ketone fragment and exhibited a high degree of oxidation. Multioketides A and B were identified as a pair of epimers featuring a rare dihydroisobenzofuranone core. Multioketide C possessed a novel 5/6/6/6 heterotetracyclic chemical architecture with unusual 1,4-dioxin functionalities. Plausible biosynthetic pathways for 1−6 were proposed. Additionally, compound 3 demonstrated weak inhibitory activities against both acetylcholinesterase and protein tyrosine phosphatase 1B.

Eudesmane-guaiane sesquiterpenoid dimers from Aucklandia costus trigger paraptosis-like cell death via ROS accumulation and MAPK hyperactivation

Three novel sesquiterpenoid heterodimers, designated as auckcostusolides A–C (1–3), were isolated from Aucklandia costus leaves. The structures of compounds 1–3 were elucidated through comprehensive spectroscopic analysis, with their absolute configurations established using a combination of X-ray single-crystal diffraction and electronic circular dichroism (ECD) calculations. Notably, compounds 1 and 2, despite sharing identical planar structures derived from two identical sesquiterpenoids, exhibited opposite configurations at C-11 and C-8′. This configurational difference can be attributed to distinct Diels−Alder cycloaddition processes between the sesquiterpenoid monomers. Additionally, the cytotoxic effects of compounds 1–3 were evaluated against colorectal cancer HCT116 cells, fibrosarcoma HT1080 cells, and hepatocellular carcinoma HepG2 cells. Compounds 1–3 induced cell death was characterized by endoplasmic reticulum (ER) swelling and cytoplasmic vacuolization, typical morphological changes associated with paraptosis. Mechanistic studies revealed that compounds 1 and 3 triggered paraptosis-like cell death through the accumulation of reactive oxygen species (ROS), activation of ER stress, and stimulation of the MAPK signaling pathway.

Highly oxygenated dihydrostilbenoids and flavones from the aerial part of Glycyrrhiza uralensis and their antimicrobial activities

Abstract Background Multidrug-resistant bacteria (MDRB) represent a significant global challenge due to their high mortality rates, substantial economic burden, and rapid spread. Traditional triple or quadruple therapies have demonstrated limited efficacy as a result of increasing drug resistance. Thus, it is urgent to develop novel anti-MDRB drugs with high efficiency and low toxicity. Objectives To isolate and identify the dihydrostilbenoids and flavones from the aerial part of Glycyrrhiza uralensis (Fabaceae) and their antimicrobial activities were screened. Materials and methods The aerial part of G. uralensis was extracted with 75% aqueous EtOH. The crude extract was repeatedly isolated by macroporous resin, silica gel, Sephadex LH-20, C18-MPLC, and MCI-MPLC, which were then purified by semipreparative RP-HPLC to obtain monomer compounds. The structures of the isolates were assigned by a combination of optical rotations, UV spectra, nuclear magnetic resonance, and high-resolution electrospray ionization mass spectrometry, and the absolute configurations of compounds 2, 3, and 7 were further confirmed by electronic circular dichroism calculations. Subsequently, we investigated their antimicrobial activities by the broth microdilution method. Results Seventeen previously undescribed phenolic compounds (1–17) and 26 known analogs (18–43), including dihydrostilbenoids, flavones, and dihydroflavones, were identified from the aerial part of G. uralensis. In vitro, antimicrobial bioassays demonstrated that compound 31 displayed the strongest inhibitory effect against 4 drug-resistant Helicobacter pylori strains (MIC = 2–4 μg/mL), comparable to metronidazole (MIC = 1–32 μg/mL). Additionally, compounds 10, 13, and 15 demonstrated bactericidal activity against Staphylococcus aureus (MIC = 4 μg/mL), while compounds 15 and 22 exhibited inactivation effects against Mycobacterium smegmatis, Enterococcus faecium, and E. faecalis (MIC = 4–8 μg/mL). Conclusions These monomeric compounds with antimicrobial activities were isolated from the aerial parts of G. uralensis, providing valuable insights into the potential anti-MDRB properties of its nonmedicinal parts.

Heterologous Expression of Type II PKS Gene Cluster Leads to Diversified Angucyclines in Streptomyces albus J1074

Heterologous expression has emerged as an effective strategy in activating Streptomyces cryptic gene clusters or improving yield. Eight compounds were successfully obtained by heterologous expression of the type II PKS gene cluster spi derived from marine Streptomyces sp. HDN155000 in the chassis host Streptomyces albus J1074. The structures with absolute configurations were elucidated using extensive MS and NMR spectroscopic methods, as well as theoretical NMR calculations and electronic circular dichroism (ECD) calculations. Interestingly, compound WS009 Z (2) contains a rare thiomethyl group, angumycinone T (4) has a novel oxo-bridge formed between C12a and C4, and angumycinone X (3) showed cytotoxicity toward K562 and NCI-H446/EP cell lines.

Biotransformation of Glaucic Acid Isolated from the Root of Lindera glauca by the Endophytic Fungi Penicillium Chrysogenum SHJ-07.

Glaucic acid isolated from the root of Lindera glauca, was investigated by the biotransformation methods via the endophytic fungi, resulting in the production of five new glausesquiterpenes A-E (1-5), along with a known analogue 6. Their structures were elucidated based on spectroscopic methods and electronic circular dichroism (ECD) calculations. In the bioassays, glausesquiterpene A (1) showed good inhibitory activity of NO production in LPS-activated RAW 264.7 macrophages with an IC50 value of 20.1 μM than positive control (Indomethacin, IC50 24.1 μM). Further in vitro studies demonstrated that glausesquiterpene A significantly suppressed the protein expression of iNOS and COX-2 at the concentration of 25.0 μM.

Penicitrisochromans A-C, new isochromans from the marine-derived fungus Penicillium citrinum PSU-MF100.

Three new isochroman derivatives, penicitrisochromans A-C (1-3), together with 25 known polyketides were isolated from the marine-derived fungus Penicillium citrinum PSU-MF100. Their structures were elucidated by extensive spectroscopic analysis. The absolute configurations of 1 and 2 were established by comparison of specific rotations and electronic circular dichroism (ECD) data with those of the known co-metabolite whereas those of 3 were assigned based on the ECD calculation and biosynthetic consideration. Among the isolated polyketides, three known anthraquinone derivatives, ω-hydroxyemodin, penicillanthranin A and emodin, displayed moderate to strong antibacterial activity against methicillin-resistant Staphylococcus aureus with MIC values of 32, 16 and 4 µg/mL, respectively. For antifungal activity, two known benzopyranones, coniochaetones A and C, exhibited moderate antifungal activity against Candida albicans NCPF3153 and Cryptococcus neoformans ATCC90112 with the respective MIC values of 16 and 64 µg/mL.

Dicitrinols A-C: Citrinin Derivatives from Hydrothermal Vent-Associated Fungus Penicillium citrinum TW132-59.

Three new unusual citrinin derivatives with a unique 6/5/7/5 core, dicitrinols A-C (1-3, respectively), were isolated via the fermentation of hydrothermal vent-associated fungus Penicillium citrinum TW132-59. Their structures were unambiguously determined by nuclear magnetic resonance, mass spectrometry, and electronic circular dichroism calculations. Dicitrinols A-C represent a novel cage carbon skeleton with a decahydro-5,9,4-(epipropane[1,1,3]triyl)cycloocta[b]furan ring system. Dicitrinols A-C showed moderate antifungal activity against Candida albicans, Cryptococcus neoformans, and Fusarium oxysporum and antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter baumannii with minimum inhibitory concentrations ranging from 4 to 16 μg/mL.

A new 2-pyrrolidinone from Cladosporium sp. associated with Rubus tephrodes

The cultivation of Cladosporium sp., a fungus found in association with Rubus tephrodes Hance, resulted in the identification of sixteen compounds. New compound cladosporlactam (1) was distinguished by featuring a skeleton linked to a furan unit, with 3,4-dihydroxypyrrolidine-2-ketone as its characteristic structure. The structure of cladosporlactam was elucidated through meticulous analyses using NMR, electronic circular dichroism (ECD) calculations. Compound 1 could cause a gradual reduction in lipid droplets in a dose-dependent manner without inducing cytotoxicity and demonstrated intermediate antimicrobial activity against Staphylococcus aureus with MIC values of 8 μg/mL.

Isolation and Identification of Monoterpenoids from Callicarpa Nudiflora.

A phytochemical and directional investigation was carried out on the leaves of Callicarpa nudiflora. Various separation methods including silica gel, sephadex LH-20, medium pressure liquid chromatography (MPLC), preparative thin-layer chromatography (p-TLC) and preparative high performance liquid chromatography (p-HPLC) were used to isolate 10 compounds. The comprehensive structural elucidation of five novel monoterpenoids (1-5) was achieved through multi-spectroscopic analyses, and advanced quantum mechanical electronic circular dichroism (ECD) calculations. Furthermore, the anti-inflammatory activity of the identified compounds was assessed.

Immunosuppressive Breviane Spiroditerpenoids from Penicillium bialowiezense Isolated from a Medicinal Plant.

Breviane spiroditerpenoids are a small group of structurally interesting and complex meroterpenoids. This work focused on an endophytic fungus Penicillium bialowiezense ZBWPQ-27 that was isolated from a medicinal plant Euphorbia neriifolia, leading to the isolation of 15 breviane spiroditerpenoids with four types of polycyclic systems (1-6 and 9-17), and two new carotane sesquiterpenoids (7 and 8). The structures including absolute configurations of the new compounds 1-8 were elucidated by spectroscopic data analysis and electronic circular dichroism (ECD) calculations. In addition, the misassigned NMR data of several resonances of the 5-methyl-TAL motif (E ring) in those of known brevianes (9-15) were corrected by spectroscopic data analysis. Biological tests revealed that brevianes with the type A ring system (6/6/6/5/6) showed moderate to significant immunosuppressive activities, and compound 11 displayed the most potent inhibitory activities against concanavalin A (ConA)-induced T cell proliferation (IC50 4.1 ± 0.2 μM) and lipopolysaccharide (LPS)-induced B cell proliferation (IC50 4.6 ± 0.2 μM), with good SI values of 28 ± 2 and 25 ± 4, respectively.

Two new guaiane-type sesquiterpene glycosides from Atractylodes Japonica Koidz. ex Kitam

Two new guaiane-type sesquiterpene glycosides, atractylodes guaianoside I (1) and atractylodes guaianoside II (2), along with eleven known sesquiterpenes (3–13), were isolated from Atractylodes Japonica Koidz. ex Kitam. The structures of these two new compounds were elucidated by extensive spectroscopic analyses and mass spectrometric techniques. And their absolute configurations were confirmed by electronic circular dichroism (ECD) calculations. In addition, the isolated compounds were evaluated for their cytotoxic activities against three cancer cell lines HT-29, A-549, and MCF-7. Results showed that new compound 2 had inhibitory effects on three types of cancer cells, while new compound 1 only had inhibitory effects on HT-29 and MCF-7.

Epimesatines P–S: Four Undescribed Flavonoids from Epimedium sagittatum Maxim. and Their Cytotoxicity Activities

In this study, four previously undescribed flavonoids, named epimesatines P (1), Q (2), R (3), and S (4), were isolated from the aerial parts of Epimedium sagittatum Maxim. Their structures and absolute configurations were confirmed via spectroscopic analyses, quantum chemical electronic circular dichroism (ECD) calculations, Mo2(OAc)4–induced ECD, and Rh2(OCOCF3)4–induced ECD experiments. Epimesatines Q and R were characterized by the presence of furan rings. A cytotoxicity assay demonstrated that epimesatines P–S exhibited significant inhibitory effects on the viability of MCF-7 human breast cancer cells, with IC50 values ranging from 1.27 to 50.3 μM. Notably, epimesatines Q and R exhibited superior efficacy against MCF-7 cells compared to epimesatines P and S, suggesting that the presence of furan rings may enhance their activity against MCF-7 cells. Specifically, epimesatine Q displayed a more potent inhibitory effect at 1.27 μM compared to a positive control, docetaxel, which had an IC50 of 2.13 μM, highlighting its potential as a therapeutic agent for breast cancer. Importantly, none of the tested compounds exhibited obvious toxicity toward MCF-10A human breast epithelial cells. Furthermore, compounds 1, 3, and 4 were found to significantly inhibit the expression of sphingosine kinase 1 (Sphk1) in MCF-7 cells.

Aspongpyridiniums A−J, amino acid-derived pyridinium salts from insect species Aspongopus chinensis

Aspongpyridiniums A-J (1-10), ten previously undescribed amino acid-derived pyridinium salts were isolated and identified from the n-BuOH fraction of the 50% MeOH extract of insect species Aspongopus chinensis, well-known for its use in traditional Chinese medicine for the treatment of pain, indigestion and kidney diseases. Their structures were determined by extensive spectroscopic data as well as electronic circular dichroism calculations and comparisons. Aspongpyridiniums A-J are structurally characterized by a unique 1,3,4-trisubstituted pyridinium skeleton with a variable functional group derived from an amino acid unit. In bioassays, Compounds 5 and 10 exhibited certain inhibitory activities against α-glucosidase, while 1-10 showed moderate to weak acetylcholinesterase inhibitory effects.

Solanapyrone analogues from endophytic Nigrospora sphaerica MZW-A associated with the endangered conifer Pinus wangii

Eight previously undescribed solanapyrone analogues, sphasolanapyrones A–H (1–8), together with four structurally related known compounds (9–12) were obtained from the solid fermentation of Nigrospora sphaerica MZW-A, an endophytic fungus isolated from the fresh branches of the endangered conifer Pinus wangii. This study represents the first investigation on the secondary metabolites of endophytic fungus associated with this precious plant. The structures and absolute configurations of compounds 1–8 were elucidated by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculations. 1 and 2 are first examples of 3,4-vic diol solanapyrone analogues, whereas 7 and 8 are rare 17-nor-solanapyrones. Among these isolates, 3, 4, 5, and 11 showed weak inhibitory against Staphylococcus aureus. In addition, compound 5 displayed weak cytotoxic effects against several tumor cell lines.

Highly oxygenated clerodane furanoditerpenoids from the leaves and twigs of Croton yunnanensis

The phytochemical investigation of the leaves and twigs of Croton yunnanensis resulted in the isolation of eight new clerodane furanoditerpenoids, named croyunfuranoids A-H (1-8), along with three known analogs (9-11). The structures of these compounds were elucidated using spectroscopic analyses, and their absolute configurations were determined through a combination of electronic circular dichroism (ECD) calculations and single-crystal X-ray diffraction. Notably, Croyunfuranoid D (4) is identified as a rare 18,19-dinor-clerodane diterpenoid. Additionally, the structure of a previously reported diterpenoid, crotonyunnan B, was revised. All isolated compounds were evaluated for their inhibitory activities on nitric oxide (NO) production in LPS-induced RAW 264.7 macrophages. Among them, compounds 5 and 6 demonstrated significant inhibitory effects, with IC50 values of 20.33 ± 2.31 and 22.80 ± 1.31 μmol·L-1, respectively.

Bioactive polyketides and tryptophol alkaloids from the endophytic fungus Botryosphaeria dothidea LE-07 of Chinese tulip tree

Two new tetraketide-derived phenol rhamnosides [botryrhamnosides A (1) and B (2)] and a new rhamnosylated tryptophol alkaloid (botryrhamnoside C, 3), along with seven related known compounds (4–10) were isolated from the solid culture of Botryosphaeria dothidea LE-07, an endophytic fungus residing in the leaves of the rare medicinal plant Chinese tulip tree (Liriodendron chinense). Their structures with the absolute configurations were determined by a combination of spectroscopy methods, comparing specific rotations, electronic circular dichroism (ECD) calculations, and single-crystal X-ray diffraction analysis. Compounds 1 and 2 are rare tetraketide-derived resorcinols incorporating a l-rhamnose moiety, while 3 represents the first example of rhamnose-bound tryptophol derivatives produced by microorganisms. These metabolites were evaluated in vitro for their antimicrobial and anti-neuroinflammation activities. The rhamnosylated derivatives 1–5 displayed potent antibacterial activity against Escherichia coli, with MIC values in the range of 8–16 μg/mL. Compound 2 attenuated neuroinflammation in lipopolysaccharide (LPS)-induced BV-2 microglial cells, by decreasing the level of pro-inflammatory mediators [nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin 6 (IL-6)] and down-regulating the mRNA expression of inducible nitric oxide synthase (iNOS). In addition, compound 8 exhibited remarkable inhibitory effect against the ATP-citrate lyase (ACL), an emerging drug target for hyperlipidemia and related glycolipid metabolic disorders, with an IC50 value of 5.32 μM.