Unified Strategy Enables the Collective Syntheses of Structurally Diverse Indole Alkaloids.

Natural products and their analogues are significant sources of therapeutic lead compounds. However, synthetic strategies for generating large collections of these molecules remain a significant challenge. The most difficult step in their synthesis is the design of a common intermediate that can be easily transformed into natural products belonging to different families. This study demonstrates the evolution of synthetic tactics designed to assemble the functionalized piperidines present in indole alkaloids from a common intermediate. More importantly, we also report a previously unknown Ir- and Er-catalyzed dehydrogenative spirocyclization reaction that enables direct access to spirocyclic oxindole alkaloids. As a practical application, the asymmetric total syntheses of 29 natural alkaloids belonging to different families were accomplished by following a uniform synthetic route. The proposed methodology extends the capability of the iridium-catalyzed dehydrogenative coupling reaction to the realm of indole-alkaloid synthesis and provides new opportunities for the efficient preparation of natural product-like molecules.

Undobolins A-L, Ophiobolin-Type Sesterterpenoids from Aspergillus undulatus.

Twelve previously undescribed ophiobolin-type sesterterpenoids, undobolins A-L (1-12), were isolated from Aspergillus undulatus, and their structures were elucidated by spectroscopic analysis, ECD calculations, and single-crystal X-ray diffraction experiments. Compound 1 was the second example of 20-nor-ophiobolin reported, while compounds 2-6 were notable for oxygenation of C-2, and compound 6 showed significant inhibitory activity against ConA-induced T lymphocyte proliferation with an IC50 value of 2.3 µM, which suggests a promising new direction in the quest for immunosuppressive agents.

Discovery of Natural Potent HMG-CoA Reductase Degraders for Lowering Cholesterol.

Exploitation of key protected wild plant resources makes great sense, but their limited populations become the major barrier. A particular strategy for breaking this barrier was inspired by the exploration of a resource-saving fungal endophyte Penicillium sp. DG23, which inhabits the key protected wild plant Schisandra macrocarpa. Chemical studies on the cultures of this strain afforded eight novel indole diterpenoids, schipenindolenes A-H (1-8), belonging to six diverse skeleton types. Importantly, semisyntheses suggested some key nonenzymatic reactions constructing these molecules and provided targeted compounds, in particular schipenindolene A (Spid A, 1) with low natural abundance. Remarkably, Spid A was the most potent HMG-CoA reductase (HMGCR) degrader among the indole diterpenoid family. It degraded statin-induced accumulation of HMGCR protein, decreased cholesterol levels and acted synergistically with statin to further lower cholesterol. Mechanistically, transcriptomic and proteomic profiling suggested that Spid A potentially activated the endoplasmic reticulum-associated degradation (ERAD) pathway to enhance the degradation of HMGCR, while simultaneously inhibiting the statin-activated expression of many key enzymes in the cholesterol and fatty acid synthesis pathways, thereby strengthening the efficacy of statins and potentially reducing the side effects of statins. Collectively, this study suggests the potential of Spid A for treating cardiovascular disease.

Cytotoxic C-20 non-oxygenated ent-kaurane diterpenoids from Isodon wardii.

Twenty new ent-kaurane diterpenoids, wardiisins A-T (1-20), along with two previously undescribed artefactual compounds (21 and 22) and twelve known analogues (23-34), were isolated from the aerial part of Isodon wardii. Their structures were elucidated by comprehensive analysis of spectroscopic data and single-crystal X-ray diffraction, and most of them were found to bear unusual C-12 oxygenation. Compounds 4, 7, 8, 19, 20, 21 exhibited remarkable cytotoxicity against the cancer cell lines HL-60, SMMC-7721, A-549, MDA-MB-231, and SW480, with IC50 values ranging from 0.3 to 5.2 µM. Moreover, 7 was found to induce G2/M cell cycle arrest and promote apoptosis in SW480 cell lines.

Pegriseofamines A-E: Five cyclopiazonic acid related indole alkaloids from the fungus Penicillium griseofulvum.

Five new cyclopiazonic acid related indole alkaloids, pegriseofamines A-E (1-5), were isolated from the fungus Penicillium griseofulvum. Their structures and absolute configurations were determined by NMR, HRESIMS, quantum-chemical calculation, and X-ray diffraction experiments. Among them, pegriseofamine A (1) possesses an undescribed 6/5/6/7 tetracyclic ring system generated by the fusion of an azepine and an indole unit via a cyclohexane, and the postulated biosynthetic origin of 1 was discussed. Compound 4 could relieve liver injury and prevent hepatocyte apoptosis in ConA-induced autoimmune liver disease.

Asymmetric Total Synthesis of Antibiotic Elansolid A.

Elansolid A is a structurally complex polyketide macrolactone natural product that exhibits promising antibacterial properties. Its challenging asymmetric total synthesis was achieved by a convergent strategy, in which the tetrahydroindane core of the molecule and an eastern vinyl iodide moiety were combined as the main fragments. The central tetrahydroindane motif was constructed with high stereoselectivity by a bioinspired intramolecular Diels-Alder cycloaddition, generating four stereogenic centers in a single step. The stereocontrol of this key step could be achieved by virtue of a 1,3-allylic strain generated by the temporary introduction of a steric-directing iodine substituent on the substrate. The formation of the macrolactone motif that completes the synthesis was achieved via two different retrosynthetic disconnections, namely, a Suzuki-Miyaura cross-coupling or an alternative Mukaiyama esterification reaction.

G protein-coupled estrogen receptor promotes acrosome reaction via regulation of Ca2+ signaling in mouse sperm†.

G protein-coupled estrogen receptor (GPER), a seven-transmembrane G protein-coupled receptor, mediates the rapid pre-genomic signaling actions of estrogen and derivatives thereof. The expression of GPER is extensive in mammal male reproductive system. However, the functional role of GPER in mouse sperm has not yet been well recognized. This study revealed that GPER was expressed at the acrosome and the mid-flagellum of the mouse sperm. The endogenous GPER ligand 17ß-estradiol and the selective GPER agonist G1 increased intracellular Ca2+ concentration ([Ca2+]i) in mouse sperm, which could be abolished by G15, an antagonist of GPER. In addition, the G1-stimulated Ca2+ response was attenuated by interference with the phospholipase C (PLC) signaling pathways or by blocking the cation channel of sperm (CatSper). Chlortetracycline staining assay showed that the activation of GPER increased the incidence of acrosome-reacted sperm. Conclusively, GPER was located at the acrosome and mid-flagellum of the mouse sperm. Activation of GPER triggered the elevation of [Ca2+]i through PLC-dependent Ca2+ mobilization and CatSper-mediated Ca2+ influx, which promoted the acrosome reaction of mouse sperm.

Analysis of risk factors for post-endoscopic papillectomy bleeding.

BACKGROUND: Endoscopic papillectomy (EP) is an effective treatment for ampullary lesions but technically challenging because of anatomical specificities concerning the high rate of adverse events. Bleeding is one of the most feared complications and can be potentially life-threatening. AIM: To study the risk factors for bleeding after EP are presented with the goal of establishing preventive measures. METHODS: A total of 173 consecutive patients with ampullary lesions undergone EP from January 2006 to October 2020 were enrolled in this study. They were divided into a bleeding group and a non-bleeding group depending on whether postoperative bleeding occurred. Related factors were analyzed by univariate and multivariate logistics regression. RESULTS: Postoperative bleeding was experienced in 33 patients (19.07%). Multivariate analysis also identified intraoperative bleeding (OR: 4.38, 95% CI: 1.87-11.15, p = .001) and endoscopic closure (OR: 0.25, 95% CI: 0.10-0.58, p = .001) as independent factors significantly associated with bleeding after EP. Lesion size (≥3 cm) was shown as an independent factor significantly associated with intraoperative bleeding (OR: 4.25, 95% CI: 1.21-16.44, p = .028). CONCLUSIONS: This retrospective evaluation found that endoscopic closure was associated with reduced risk and intraoperative bleeding with increased risk of bleeding after EP. Lesion size may indirectly influence the risk of postoperative bleeding by increasing the risk of intraoperative bleeding.

Spiroligustolides A and B: Two pairs of enantiomeric spiro-orthoester-containing phthalide dimers as Cav3.1 calcium channel inhibitors from Ligusticum Chuanxiong Hort.

Two pairs of unprecedented enantiomeric phthalide dimers, spiroligustolides A (1a/1b) and B (2a/2b), featuring a unique spiroorthoster linkage between two monomeric units to form a 5/6/5/6/6-fused ring system, were isolated from the roots of Ligusticum chuanxiong. The structures and relative configurations of 1 and 2 were determined by HR-ESI-MS, IR, and NMR spectroscopic data, coupled with single-crystal X-ray diffraction analysis, and the absolute configurations of 1a, 1b, 2a, and 2b were established by comparing the experimental and calculated electronic circular dichroism (ECD) data. Plausible biosynthetic pathway for 1 and 2 was proposed. Moreover, compounds 1, 1b, and 2b showed remarkable inhibitory activities on Cav3.1 calcium channel with IC50 values of 8.34, 7.08, and 8.60 µM, respectively.

Scopariusicides D-M, ent-clerodane-based isomeric meroditerpenoids with a cyclobutane-fused γ/δ-lactone core from Isodon scoparius.

Scopariusicides D-M (1-10), ten new ent-clerodane-based meroditerpenoids with a cyclobutane-fused γ/δ-lactone core, were isolated from Isodon scoparius. Their structures were determined by comprehensive analysis of spectroscopic data, single-crystal X-ray diffraction, chemical transformation, and TDDFT ECD calculation. A plausible biosynthetic pathway of 1-10 was proposed in which the asymmetrical cyclobutane ring was formed via a crossed "head-to-tail" intermolecular [2 + 2] cycloaddition in anti/syn facial approaches between an ent-clerodane lactone and a cis-4-hydroxycinnamic acid. Bioactivity evaluation manifested that 5 exhibited significant neuroprotective effect against corticosterone-induced injury in PC12 cells, while 6 and 7 exhibited moderate immunosuppressive activity against human T cell proliferation stimulated by anti-CD3/anti-CD28 mAb.

Structurally diverse diterpenoids from Isodon oresbius and their bioactivity.

Twelve new diterpenoids, isoresbins A-L (1-12), together with twenty-eight known ones, were isolated from the aerial parts of Isodon oresbius. Their diverse structures included 6,7-seco-ent-kaurane, 7,20-epoxy-ent-kaurane, 6,7:8,15-diseco-ent-kaurane, and abietanes skeletons, which were elucidated by spectroscopic data interpretation, single-crystal X-ray diffraction, and quantum chemical calculation. Isoresbins A (1) and B (2) possessed a new rearranged 15(8 â†’ 11)-abeo-6,7-seco-ent-kaurane skeleton. 1 and 5 promoted lysosomal function, which was evaluated by LysoTracker Red staining and DQ-ovalbumin dequenching assay. 1 showed cytotoxicity against six human tumor cell lines with IC50 values in 2.07-4.04 µM range. Moreover, 1 induced damage of mitochondrial membrane potential, G2/M cell cycle arrest and apoptosis in SW480 cells.

Association between the cut-off value of the first trimester fasting plasma glucose level and gestational diabetes mellitus: a retrospective study from southern China.

PURPOSE: Our previous studies have suggested that the first trimester fasting plasma glucose (FPG) level is associated with gestational diabetes mellitus (GDM) and is a predictor of GDM. The aim of the present study was to provide valuable insights into the accuracy of the first trimester FPG level in the screening and diagnosis of GDM in southern China. METHODS: This retrospective study included pregnant women who had their first trimester FPG level recorded at 9-13+6 weeks and underwent screening for GDM using the 2-h 75 g oral glucose tolerance test (OGTT) between the 24th and 28th gestational weeks. Differences between the GDM and non-GDM groups were assessed by Student's t test and the chi-squared test according to the nature of the variables. A restricted cubic spine was used to explore the relationship between the first trimester FPG level and the odds ratio (OR) of GDM in pregnant women. Cut-off values of first trimester FPG were determined using receiver operating characteristic (ROC) curves and the area under the curve (AUC), and 95% confidence intervals (CIs), the positive predictive value (PPV) and the negative predictive value (NPV) were calculated. RESULTS: The medical records of 28,030 pregnant women were analysed, and 4,669 (16.66%) of them were diagnosed with GDM. The average first trimester FPG level was 4.62 ± 0.37 mmol/L. The OR of GDM increased with increasing first trimester FPG levels and with a value of first trimester FPG of approximately 4.6 mmol/L, which was equal to 1 (Chi-Square = 665.79, P < 0.001), and then started to increase rapidly afterwards. The ROC curve for fasting plasma glucose in the first trimester (4.735 mmol/L) for predicting gestational diabetes mellitus in pregnant women was 0.608 (95% CI: 0.598-0.617), with a sensitivity of 0.490 and a specificity of 0.676. CONCLUSION: Based on the research, we recommend that all pregnant women undergo FPG testing in the first trimester, particularly at the first antenatal visit. Furthermore, we suggest that the risks of GDM should be given increased attention and management as soon as the first trimester FPG value is more than 4.7 mmol/L. First trimester FPG levels should be considered a screening marker when diagnosing GDM in pregnant women but this needs to be confirmed by more prospective studies. These factors may have a significant impact on the clinical treatment of pregnant women.

Anti-Neuroinflammatory Activity of New Naturally Occurring Benzylated Hydroxyacetophenone Analogs from the Endophytic Fungus Alternaria sp. J030.

Chemical studies on the culture broth of the endophytic fungus Alternaria sp. J030 led to the identification of three benzylated hydroxyacetophenone derivatives, bauvaroalterins A-C (1-3), and 34 structurally diverse metabolites (4-37). The new structures were elucidated by extensive spectroscopic analyses including UV, IR, 1D and 2D NMR, HR-ESI-MS, and further confirmed using single crystal X-ray diffraction. The in vitro anti-neuroinflammatory effects of the co-isolated metabolites were evaluated in lipopolysaccharide (LPS)-stimulated microglial cells. Compounds 1-3 were shown to significantly reduce LPS-induced NO production by inhibiting the expression of iNOS, as well as inhibiting LPS-induced production of the inflammatory factors TNF-α, IL-1ß and IL-6. Further studies revealed that 1-3 were capable of down-regulating the expression of NF-κB subunits p50 and p65, thereby suppressing the activation of NF-κB by inhibiting the LPS-induced phosphorylation of IκB-α. Together these findings demonstrate that bauvaroalterins A-C (1-3) exert anti-neuroinflammatory effects via inhibition of the NF-κB/iNOS signalling pathway in LPS induced BV-2 cells.

Genome-Wide Identification and Characterization of YUCCA Gene Family in Mikania micrantha.

Auxin is a general coordinator for growth and development throughout plant lifespan, acting in a concentration-dependent manner. Tryptophan aminotransferases (YUCCA) family catalyze the oxidative decarboxylation of indole-3-pyruvic acid (IPA) to form indole-3-acetic acid (IAA) and plays a critical role in auxin homeostasis. Here, 18 YUCCA family genes divided into four categories were identified from Mikania micrantha (M. micrantha), one of the world's most invasive plants. Five highly conserved motifs were characterized in these YUCCA genes (MmYUCs). Transcriptome analysis revealed that MmYUCs exhibited distinct expression patterns in different organs and five MmYUCs showed high expression levels throughout all the five tissues, implying that they may play dominant roles in auxin biosynthesis and plant development. In addition, MmYUC6_1 was overexpressed in DR5::GUS Arabidopsis line to explore its function, which resulted in remarkably increased auxin level and typical elevated auxin-related phenotypes including shortened roots and elongated hypocotyls in the transgenic plants, suggesting that MmYUC6_1 promoted IAA biosynthesis in Arabidopsis. Collectively, these findings provided comprehensive insight into the phylogenetic relationships, chromosomal distributions, expression patterns and functions of the MmYUC genes in M. micrantha, which would facilitate the study of molecular mechanisms underlying the fast growth of M. micrantha and preventing its invasion.

Immunosuppresive Sesterterpenoids and Norsesterterpenoids from Colquhounia coccinea var. mollis.

A pair of new C-14 epimeric sesterterpenoids, colquhounoid D (1) and 14-epi-colquhounoid D (2), and five degradation products featuring new C20 and C21 frameworks, norcolquhounoids A-E (3-7), were isolated from Colquhounia coccinea var. mollis. Their structures were elucidated by comprehensive spectroscopic analysis and single-crystal X-ray diffraction. Degradation of the C25 skeleton to the C21 skeleton was also achieved using aqueous NaIO4 and RuCl3. Compounds 1 and 2 showed significant immunosuppressive activity on the cytokine IFN-γ secretion of mouse splenocytes induced by anti-CD3/CD4 monoclonal antibodies, with IC50 of 8.38 and 5.79 µM, respectively, and compounds 5 and 6 were moderately active.

Neuroprotective schinortriterpenoids from Schisandra neglecta collected in Medog County, Tibet, China.

Schisdilactones K-U (1-11), a series of previously unreported 16,17-secopreschisanartane-type schinortriterpenoids (SNTs), were isolated from the leaves and stems of Schisandra neglecta A. C. Smith. Their structures were mainly established through analysis of their spectroscopic data. Besides, schisdilactones K (1), O (5) and R (8) were confirmed by single-crystal X-ray crystallographic analysis, and the configurations of schisdilactones T and U (10 and 11) were elucidated via quantum chemical calculation of their NMR chemical shifts and electronic circular dichroism (ECD) spectra. Schisdilactones L-S (2-8) and U (11) were found to exhibit moderate protective activities against corticosterone-induced apoptosis of PC12 cells at 20 µM, with cell viability in the range of 62.95-66.97%.

Bisabolane, cadinane, and cyclonerane sesquiterpenes from an algicolous strain of Trichoderma asperelloides.

Ten new bisabolane derivatives, trichobisabolins Q-Z (1-10), one new cadinane derivative, cadin-4-en-11-ol (11), and three new cyclonerane derivatives, cycloner-3-en-7,11-diol (12), isoepicyclonerodiol oxide (13), and norepicyclonerodiol oxide (14), were isolated from the endophytic fungal strain RR-dl-6-11 of Trichoderma asperelloides that was obtained from a marine alga. Their structures along with relative configurations were established mainly by NMR and IR as well as MS techniques, and the absolute configurations of 10 and 11 were assigned by ECD and X-ray diffraction data, respectively. Sesquiterpenes from the fungus T. asperelloides are reported for the first time. It is interesting that half of the bisabolane derivatives are demethylated. Compound 12 represents the first the occurrence of cyclopentenyl-bearing cycloneranes, and 14 seems a cyclopentyl-degrading cyclonerane derivative. Several isolates feature potent inhibition of marine phytoplankton species.

Pesimquinolones I-S, eleven new quinolone alkaloids produced by Penicillium simplicissimum and their inhibitory activity on NO production.

Eleven undescribed quinolone alkaloids, pesimquinolones I-S (1-4 and 6-12), as well as eleven known congeners (5 and 13-22), were isolated from the solid culture broth of the fungus Penicillium simplicissimum. Their chemical structures with absolute configurations were established by a combination of NMR spectroscopy, single-crystal X-ray crystallography, and modified Mosher's methods. Pesimquinolones I-K (1-3) represent the first examples of natural occurring quinolone alkaloids that possess a 6/6/6/6 tetracyclic ring system. The anti-inflammatory activities of selected compounds on LPS-induced nitric oxide (NO) production in adherent cells were evaluated. Compounds 1 and 2 showed suppressive effects on the production of NO, with IC50 values of 10.13 and 8.10 µM, respectively.

(-)-Isoscopariusin†A, a Naturally Occurring Immunosuppressive Meroditerpenoid: Structure Elucidation and Scalable Chemical Synthesis.

(-)-Isoscopariusin A was isolated from the aerial parts of Isodon scoparius. Chemical synthesis and spectroscopic analysis established its structure as an unsymmetrical meroditerpenoid bearing a sterically congested 6/6/4 tricyclic carbon skeleton with seven continuous stereocenters. A gram-scale synthesis was achieved in 12 steps from commercially available (+)-sclareolide. A cobalt catalyzed, hydrogen atom transfer-based olefin isomerization was used to prepare a trisubstituted alkene, which underwent stereoselective [2+2] cycloaddition with a substituted keteniminium ion generated in situ from the corresponding amide. The cyclobutanone product was further elaborated into the fully substituted cyclobutane core through face-selective homologation, and the two side chains were installed by using nickel-catalyzed cross-electrophile coupling and carbodiimide-mediated esterification, respectively. (-)-Isoscopariusin A displayed selective inhibition of T-cell proliferation.

Posttranslational lysine 2-hydroxyisobutyrylation of human sperm tail proteins affects motility.

STUDY QUESTION: Does lysine 2-hydroxyisobutyrylation, a newly identified protein posttranslational modification (PTM), occur in human sperm and affect human sperm function? SUMMARY ANSWER: Lysine 2-hydroxyisobutyrylation mainly occurs in human sperm tail proteins, and excessive lysine 2-hydroxyisobutyrylation affects human sperm motility. WHAT IS KNOWN ALREADY: PTM is regarded as an important pathway in regulating sperm function since mature sperm are almost transcriptionally silent. However, only phosphorylation was extensively studied in mature sperm to date. Lysine 2-hydroxyisobutyrylation, a newly characterised PTM, is broadly conserved in both eukaryotic and prokaryotic cells. Although histone lysine 2-hydroxyisobutyrylation has been shown to be associated with active gene expression in spermatogenic cells, the presence, regulatory elements and function of lysine 2-hydroxyisobutyrylation have not been characterised in mature sperm. STUDY DESIGN, SIZE, DURATION: Sperm samples were obtained from normozoospermic men and asthenozoospermic men who visited the reproductive medical centre at Jiangxi Provincial Maternal and Child Health Hospital, Nanchang, Jiangxi, China, between May 2017 and November 2018. In total, 58 normozoospermic men and 65 asthenozoospermic men were recruited to participate in this study. PARTICIPANTS/MATERIALS, SETTING, METHODS: Lysine 2-hydroxyisobutyrylation was examined using immunoblotting and immunofluorescence assays using a previously qualified pan anti-lysine 2-hydroxyisobutyrylation antibody. The immunofluorescence assay was imaged using super-resolution structured illumination microscopy. Sperm viability was examined by using the eosin staining method, and sperm motility parameters were assessed by computer-assisted sperm analysis. Sperm penetration ability was determined by evaluating the ability of the sperm to penetrate a 1% (w/v) methylcellulose solution. The level of intracellular adenosine triphosphate (ATP) was detected using a rapid bioluminescent ATP assay kit. MAIN RESULTS AND THE ROLE OF CHANCE: Lysine 2-hydroxyisobutyrylation was present in several proteins (20-100 kDa) mainly located in the tail of human sperm. Sperm lysine 2-hydroxyisobutyrylation was derived from 2-hydroxyisobutyrate (2-Hib) and was regulated by acyltransferase P300 and nicotinamide adenine dinucleotide-dependent lysine deacylase sirtuins. Elevation of sperm lysine 2-hydroxyisobutyrylation by 2-Hib decreased total motility, progressive motility, penetration ability and ATP level of human sperm. Interestingly, the level of sperm lysine 2-hydroxyisobutyrylation was higher in asthenozoospermic men than that in normozoospermic men and was negatively correlated with the progressive motility of human sperm. Furthermore, high levels of lysine 2-hydroxyisobutyrylation in asthenozoospermic men accompanied decreased ATP levels. LIMITATIONS, REASONS FOR CAUTION: Although the present study indicated the involvement of sperm lysine 2-hydroxyisobutyrylation in regulating human sperm motility, the underlying mechanism needs to be further illustrated. WIDER IMPLICATIONS OF THE FINDINGS: The findings of this study provide insight into the novel role of lysine 2-hydroxyisobutyrylation in human sperm and suggest that abnormality of sperm lysine 2-hydroxyisobutyrylation may be one of the causes for asthenozoospermia. STUDY FUNDING/COMPETING INTEREST(S): National Natural Science Foundation of China (81771644 to T.L. and 81871207 to H.C.); Natural Science Foundation of Jiangxi province (20171ACB21006). The authors have no conflicts of interest to declare.