Alpneumines A–H,new anti-melanogenic indole alkaloids from Alstonia pneumatophora

Eight new indole alkaloids, alpneumines A–H (1–8) were isolated from the Malaysian Alstonia pneumatophora (Apocynaceae) and their structures were determined by MS and 2D NMR spectroscopic methods. Alpneumines E and G (5 and 7), vincamine, and apovincamine showed anti-melanogenesis in B16 mouse melanoma cells.     

Intermittent high glucose induces pyroptosis of rat H9C2 cardiomyocytes via sodium–glucose cotransporter 1

Molecular and Cellular Biochemistry - Cardiomyocyte death is an important pathogenic process in cardiac complications of diabetes. Diabetic patients often suffer glycemic variability. Pyroptosis is...     

How should we monitor the cardiovascular benefit of sodium–glucose cotransporter 2 inhibition?

Background

High N-terminal pro-brain-type natriuretic peptide levels have been associated with a lower risk of type 2 diabetes mellitus (T2D). However, less is known about other cardiac stress biomarkers in this context. Here we evaluated the association of mid-regional pro-atrial natriuretic peptide (MR-proANP), C-terminal pro-arginine vasopressin (copeptin), C-terminal pro-endothelin-1 (CT-proET-1) and mid-regional pro-adrenomedullin (MR-proADM) with incident T2D and changes in glucose metabolism.

Methods

We performed a prospective cohort study using data from the population-based KORA F4/FF4 study. 1773 participants (52.3% women) with MR-proANP measurements and 960 (52.7% women) with copeptin, CT-proET-1 and MR-proADM measurements were included. We examined associations of circulating plasma levels of MR-proANP, copeptin, CT-proET-1 and MR-proADM with incident T2D, the combined endpoint of incident prediabetes/T2D and with fasting and 2 h-glucose, fasting insulin, HOMA-IR, HOMA-B and HbA1c at follow-up. Logistic and linear regression models adjusted for age, sex, waist circumference, height, hypertension, total/HDL cholesterol ratio, triglycerides, smoking, physical activity and parental history of diabetes were used to compute effect estimates.

Results

During a median follow-up time of 6.4 years (25th and 75th percentiles: 6.0 and 6.6, respectively), 119 out of the 1773 participants and 72 out of the 960 participants developed T2D. MR-proANP was inversely associated with incident T2D (odds ratio [95% confidence interval]: 0.75 [0.58; 0.96] per 1-SD increase of log MR-proANP). Copeptin was positively associated with incident prediabetes/T2D (1.29 [1.02; 1.63] per 1-SD increase of log copeptin). Elevated levels of CT-proET-1 were associated with increased HOMA-B at follow-up, while elevated MR-proADM levels were associated with increased fasting insulin, HOMA-IR and HOMA-B at follow-up. These associations were independent of previously described diabetes risk factors.

Conclusions

High plasma concentrations of MR-proANP contributed to a lower risk of incident T2D, whereas high plasma concentrations of copeptin were associated with an increased risk of incident prediabetes/T2D. Furthermore, high plasma concentrations of CT-proET-1 and MR-proADM were associated with increased insulin resistance. Our study provides evidence that biomarkers implicated in cardiac stress are associated with incident T2D and changes in glucose metabolism.

     

Sodium–glucose cotransporter inhibitors and oxidative stress: An update

Sodium–glucose cotransporter 2 (SGLT2) inhibitors are therapeutic agents that have been used recently to reduce tubular absorption of glucose, leading to enhanced glycosuria, resulting in the reduction of blood glucose and improved diabetes control. Recent data suggest that SGLT2 inhibitors have antioxidant properties that may be key to the reduction in cardiovascular death found in clinical trials. Oxidative stress is involved in the development and progression of atherosclerosis, as well as underlying diabetes complications, and may result from either increased free-radical production, a reduction in antioxidative capacity, or a combination of both. In this report, we have reviewed the recent evidence of the impact that SGLT2 inhibition may have on improved oxidative stress by either amelioration of free-radical generation or potentiation of cellular antioxidative capacity, and its importance in the prevention of cardiovascular and diabetes complications.     

Aspidospermatan–aspidospermatan and eburnane-sarpagine bisindole alkaloids from Leuconotis

Leucofoline and leuconoline, representing the first members of the aspidospermatan–aspidospermatan and eburnane-sarpagine subclasses of the bisindole alkaloids, respectively, were isolated from the Malayan Leuconotis griffithii. The structures of these bisindole alkaloids were established using NMR and MS analysis, and in the case of leuconoline, confirmed by X-ray diffraction analysis. Both alkaloids showed weak cytotoxicity towards human KB cells.     

Evidence for Na+–glucose cotransporter in type I alveolar epithelium

Functional evidence of Na⁺–glucose cotransport in rat lung has been provided by Basset et al. (J. Physiol. 384:325–345, 1987). By autoradiography [³H]phloridzin binding has been found confined to alveolar epithelial type II cells in mouse and rabbit lungs (Boyd, J. Physiol. 422: 44P, 1990). In this research we checked by immunofluorescence whether Na⁺–glucose cotransporter (SGLT1) is also expressed in alveolar type I cells. Lungs of anesthetized rats and lambs were fixed by paraformaldehyde, perfused in pulmonary artery, or instilled into a bronchus, respectively. Tissue blocks embedded in paraffin or frozen were sectioned. Two specific anti-SGLT1 antibodies for rat recognizing aminoacid sequence 402–420, and 546–596 were used in both species. Bound primary antibody was detected by secondary antibody conjugated to fluorescein isothiocianate or Texas red, respectively. In some sections cellular nuclei were also stained. In rats alveolar type I cells were identified by fluorescent Erythrina cristagalli lectin. Sections were examined by confocal laser-scanning microscope. Both in rats and lambs alveolar epithelium was stained by either antibody; no labeling occurred in negative controls. Hence, SGLT1 appears to be also expressed in alveolar type I cells. This is functionally relevant because type I cells provide 95–97% of alveolar surface, and SGLT1, besides contributing to removal of lung liquid under some circumstances, keeps low glucose concentration in lining liquid, which is useful to prevent lung infection.     

Sodium–glucose cotransporter 2 inhibitors and inflammation in chronic kidney disease: Possible molecular pathways

Clinical trials with sodium–glucose cotransporter 2 (SGLT2) inhibitors (empagliflozin, dapagliflozin, and canagliflozin) have shown a decrease in the progression of chronic kidney disease (CKD). SGLT2 inhibitors represent a new category of oral antidiabetic agents that can also reduce systolic and diastolic blood pressure, as well as serum uric acid, and improve the glomerular filtration rate. Apart from affecting renal hemodynamics and glycotoxicity, evidence suggests that SGLT2 inhibitors may be renoprotective due to their effects on inflammation in renal tissues. Inflammatory responses play a prominent role in the pathophysiology of CKD as several structural and functional disorders of renal failure are strongly related to the overproduction of proinflammatory mediators. The present review discusses the anti-inflammatory properties of SGLT2 inhibitors. The different molecular pathways through which SGLT2 inhibitors may affect inflammation in the kidneys are also commented upon.     

(−)-Epilamprolobine and its N-oxide,lupin alkaloids from Sophora tomentosa

From the fresh leaves of Sophora tomentosa, three new lupin alkaloids, (?)-epilamprolobine, (+)-epilamprolobine N-oxide and 5-(3′-methoxycarbonylbutyroyl)aminomethyl-trans-quinolizidine N-oxide, have further been isolated along with (+)-matrine, (+)-matrine N-oxide, (+)-sophocarpine N-oxide, (?)-anagyrine, (?)- baptifoline, (?)-cytisine, (?)-N-methylcytisine, (?)-N-formylcytisine, (?)-N-acetylcytisine and (±)-ammodendrine. The absolute configurations of (+)-epilamprolobine N-oxide (1R:5R:6S) and (?)-epilamprolobine (5R:6S) have also been established by spectroscopic data and by comparison with synthetic (+)-epilamprolobine (5S:6R)derived from (?)-lupinine (5R:6R). (?)-Epilamprolobine is a diastereomer of (+)-lamprolobine (5R:6R) in Lamprolobium fruticosum and 5-(3′-methoxycarbonylbutyroyl) aminomethyl-trans-quinolizidine N-oxide is presumed to be an artefact. A biosynthetic pathway for the formation of (?)-epilamprolobine is also proposed.     

Purification and biochemical characterization of glucose–cellobiose-tolerant cellulases from Scytalidium thermophilum

Two cellulases from Scytalidium thermophilum were purified and characterized, exhibiting tolerance to glucose and cellobiose. Characterization of purified cellulases I and II by mass spectrometry revealed primary structure similarities with an exoglucanase and an endoglucanase, respectively. Molecular masses were 51.2 and 45.6 kDa for cellulases I and II, respectively, as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Cellulases I and II exhibited isoelectric points of 6.2 and 6.9 and saccharide contents of 11 and 93 %, respectively. Optima of temperature and pH were 60–65 °C and 4.0 for purified cellulase I and 65 °C and 6.5 for purified cellulase II. Both cellulases maintained total CMCase activity after 60 min at 60 °C. Cysteine, Mn²⁺, dithiotreitol and ß-mercaptoethanol-stimulated cellulases I and II. The tolerance to cellulose hydrolysis products and the high thermal stabilities of Scytalidium cellulases suggest good potential for industrial applications.     

Ecliptamines A–D,four new guanidine alkaloids from Eclipta prostrata L.

Four structurally unique guanidine alkaloids ecliptamines A–D (1–4) and one known analog (5) were isolated from the aerial parts of Eclipta prostrata (Asteraceae). Their structures were elucidated on the basis of spectroscopic analyses and chemical methods. The inhibitory activities of 1, 2 and 5 were assayed with respect to cyclooxygenase-1 (COX-1) and -2 (COX-2). Compound 5 showed moderate inhibitory activities against COX-1 and -2 with IC₅₀ values of 3.0 × 10⁻³ M and 8.3 × 10⁻⁴ M, respectively, whereas aspirin as a positive control displayed the IC₅₀ values of 4.2 × 10⁻⁴ M (against COX-1) and 7.1 × 10⁻⁴ M (against COX-2).     

Venezuelines A–G,new phenoxazine-based alkaloids and aminophenols from Streptomyces venezuelae and the regulation of gene target Nur77

Five new phenoxazine-based alkaloids venezuelines A–E (1–5) and two new aminophenols venezuelines F–G (6–7), as well as three known analogues exfoliazone, chandrananimycin D and carboxyexfoliazone were isolated from the fermentation broth of the marine-derived bacterium Streptomyces venezuelae. The structures of new compounds were determined on the basis of extensive spectroscopic analysis. The cytotoxic activity of these compounds against a panel of tumor cell lines were tested, while the regulation of gene target Nur77 of 2 and exfoliazone (8) were evaluated.     

Biochemical retrosynthesis of 2′-deoxyribonucleosides from glucose, acetaldehyde, and a nucleobase

2′-Deoxyribonucleosides are important as building blocks for the synthesis of antisense drugs, antiviral nucleosides, and 2′-deoxyribonucleotides for polymerase chain reaction. The microbial production of 2′-deoxyribonucleosides from simple materials, glucose, acetaldehyde, and a nucleobase, through the reverse reactions of 2′-deoxyribonucleoside degradation and the glycolytic pathway, was investigated. The glycolytic pathway of baker’s yeast yielded fructose 1,6-diphosphate from glucose using the energy of adenosine 5′-triphosphate generated from adenosine 5′-monophosphate through alcoholic fermentation with the yeast. Fructose 1,6-diphosphate was further transformed to 2-deoxyribose 5-phosphate in the presence of acetaldehyde by deoxyriboaldolase-expressing Escherichia coli cells via d-glyceraldehyde 3-phosphate. E. coli transformants expressing phosphopentomutase and nucleoside phosphorylase produced 2′-deoxyribonucleosides from 2-deoxyribose 5-phosphate and a nucleobase via 2-deoxyribose 1-phosphate through the reverse reactions of 2′-deoxyribonucleoside degradation. Coupling of the glycolytic pathway and deoxyriboaldolase-catalyzing reaction efficiently supplied 2-deoxyribose 5-phosphate, which is a key intermediate for 2′-deoxyribonucleoside synthesis. 2′-Deoxyinosine (9.9 mM) was produced from glucose, acetaldehyde, and adenine through three-step reactions via fructose 1,6-diphosphate and then 2-deoxyribose 5-phosphate, the molar yield as to glucose being 17.8%.     

Structure–activity relationship of antiparasitic and cytotoxic indoloquinoline alkaloids,and their tricyclic and bicyclic analogues

Based on the indoloquinoline alkaloids cryptolepine (1), neocryptolepine (2), isocryptolepine (3) and isoneocryptolepine (4), used as lead compounds for new antimalarial agents, a series of tricyclic and bicyclic analogues, including carbolines, azaindoles, pyrroloquinolines and pyrroloisoquinolines was synthesized and biologically evaluated. None of the bicyclic compounds was significantly active against the chloroquine-resistant strain Plasmodium falciparum K1, in contrast to the tricyclic derivatives. The tricyclic compound 2-methyl-2H-pyrido[3,4-b]indole (9), or 2-methyl-β-carboline, showed the best in vitro activity, with an IC₅₀ value of 0.45 μM against P. falciparum K1, without apparent cytotoxicity against L6 cells (SI > 1000). However, this compound was not active in the Plasmodium berghei mouse model. Structure–activity relationships are discussed and compared with related naturally occurring compounds.     

Dicorynamine and harmalan-N-oxide,two new β-carboline alkaloids from Dicorynia guianensis Amsh heartwood

The chemical investigations of Dicorynia guianensis heartwood led to the isolation of four new indole alkaloids for the first time in this plant. Compound (1) identified as spiroindolone 2′,3′,4′,9′-tetrahydrospiro [indoline-3,1′pyrido[3,4-b]-indol]-2-one, and compound (3) described as nitrone 1-methyl-4,9-dihydro-3H-pyrido [3,4-b] indole 2-oxide and were isolated for the first time as natural products. ABTS antioxidant activity guided their isolation.     

Purpuroines A–J,halogenated alkaloids from the sponge Iotrochota purpurea with antibiotic activity and regulation of tyrosine kinases

Ten new halogenated alkaloids named purpuroines A–J (1–10), and a known analogue (11), were isolated from the marine sponge Iotrochota purpurea. Their structures were elucidated by extensive spectroscopic (IR, MS, 1D and 2D NMR) data analyses. The inhibitory activity of some compounds against a panel of human disease related fungi and bacteria are evaluated. Bioassay for the regulation of tyrosine kinases revealed compounds 1 and 4 possessing selective inhibition against the kinase LCK. Primary structure–activity relationship is discussed.     

Anticancer and α-chymotrypsin inhibiting diterpenes and triterpenes from Salvia leriifolia

Salvialeriol (1), a new abietane-type diterpene, was isolated from Salvia leriifolia Benth. (Salvia leriaefolia), along with two known abietane-type diterpenoids, 6-hydroxysalvinolone (2) and deacetylnemorone (3), and two known triterpenes, 2-acetoxylupeol (4), and lupine-2,3-diol (5). Compounds 2–5 are reported here for the first time from this species. Compound 4 was previously reported as a synthetic derivative of 5 and this is the first report of its isolation from a natural source. Compounds 2, 3 and 5 exhibited a potent antiproliferative activity against the prostate cancer cell lines (PC3) with IC₅₀ of 3.9 ± 0.1, 6.2 ± 0.1 and 2.8 ± 0.1 μM, respectively, and cervical cancer cell lines (HeLa) with IC₅₀ of 8.0 ± 0.3, 2.6 ± 0.1 and 2.7 ± 0.1 μM, respectively. Whereas compounds 1 and 4 showed moderate antiproliferative activities against the cell lines. Compounds 1–5 were also evaluated for the inhibition of α-chymotrypsin, a protease enzyme, and 2 exhibited a competitive inhibition of the enzyme (IC₅₀ = 188.8 μM).     

Chrotacumines G–J,chromone alkaloids from Dysoxylum acutangulum with osteoclast differentiation inhibitory activity

Four new chromone alkaloids, chrotacumines G–J (1–4), have been isolated from the barks of Dysoxylum acutangulum. Their structures and absolute configurations were elucidated on the basis of NMR and CD data. Chrotacumines G and J (1 and 4) showed osteoclast differentiation inhibitory activity in a dose dependent manner.     

Gynostemosides A–E,megastigmane glycosides from Gynostemma pentaphyllum

Megastigmane glycosides (1–5) together with seven (6–12) related known compounds were isolated from the whole plants of Gynostemma pentaphyllum. The structures were elucidated by means of spectroscopic methods, including 2D NMR, HR-ESIMS, and circular dichroism (CD), as well as chemical transformations to be (3R, 4R, 5S, 6S, 7E)-3,4,6-trihydroxymegastigmane-7-en-9-one-3-O-β-d-glucopyranoside (gynostemoside A, 1), (3S, 4S, 5R, 6R, 7E, 9R)-3,4,6,9-tetrahydroxymegastigmane-7-en-3-O-β-d-glucopyranoside (gynostemoside B, 2), (3S, 4S, 5S, 6S, 7E, 9R)-3,4,9-trihydroxymegastigmane-7-en-9-O-β-d-glucopyranoside (gynostemoside C, 3), (3S, 4S, 5S, 6S, 7E, 9R)-3,4,9-trihydroxymegastigmane-7-en-3-O-β-d-glucopyranoside (gynostemoside D, 4), and (3S, 4S, 5S, 6S, 7E, 9R)-3,4,9-trihydroxymegastigmane-7-en-4-O-β-d-glucopyranoside (gynostemoside E, 5), respectively.     

Evolvosides C–E,flavonol-4-O-triglycosides from Evolvulus alsinoides and their anti-stress activity

Phytochemical investigation of the n-butanol fraction of Evolvulus alsinoides (Linn.) led to the isolation of three new phenolic glycosides, evolvosides C, D and E (1–3) along with six known compounds (4–9). The structures of the compounds were elucidated on the basis of spectroscopic analysis, viz. 1D and 2D NMR experiments, chemical study, and comparison with literature data. Evolvoside C (1) was characterized as kaempferol 4′-O-β-d-glucopyranosyl-(1→2)-α-l-rhamnopyranosyl-(1→6)-β-d-glucopyranoside, whereas evolvosides D and E (2–3) were found to be mono and di-O-methyl derivatives of 1. The new compounds (1–3) represent rare triglycoside derivatives of flavonol at C-4′. The isolated compounds (1–6) were screened for acute stress-induced biochemical changes in male Sprague–Dawley rats at a dose of 40 mg/kg body weight. Compounds 1 and 2 displayed anti-stress effects by normalizing hyperglycemia, plasma corticosterone, plasma creatine kinase, and adrenal hypertrophy. Compounds 3 and 6 were also found to be effective in normalizing most of these stress parameters, whereas compounds 4 and 5 were ineffective in normalizing most of these effects.     

Anaplerosis from glucose, α-ketoisocaproate, and pyruvate in pancreatic islets, INS-1 cells and liver mitochondria

Methyl succinate (MS) and alpha-ketoisocaproate (KIC) when applied alone to cultured pancreatic islets or INS-1 832/13 cells do not stimulate insulin release. However, when the two metabolites are combined together they strongly stimulate insulin release. Studying the possible explanations for this complementarity has provided clues to the pathways involved in insulin secretion. MS increased carbon incorporation of KIC into acid-precipitable material and lipid in INS-1 cells. In isolated mitochondria, MS alone increased malate, but MS plus KIC increased citrate, alpha-ketoglutarate, and isocitrate. These data and the known pathways of their metabolism suggest that MS supplies the oxaloacetate component of citrate and KIC supplies the acetate component of citrate. Other citric acid cycle intermediates can be formed from citrate enabling anaplerosis to supply precursors for extramitochondrial pathways. In addition, KIC, glucose and pyruvate can be metabolized to acetoacetate. In an INS-1 cell line deficient in ATP citrate lyase, incorporation of carbon from pyruvate into acid-precipitable material and lipid was not lowered. This negative result is in agreement with our recent discovery that citrate is not the only carrier of acyl groups from the mitochondria to the cytosol in the beta cell and that acetoacetate can also transfer acyl carbon to the cytosol.