Oleandrigenin

Development of alpha-Selective Glycosylation with l-Oleandral and Its Application to the Total Synthesis of Oleandrin.[Pubmed:36739571]

Org Lett. 2023 Feb 17;25(6):966-971.

This letter describes the development of an alpha-selective glycosylation using l-oleandrose, a 2-deoxysugar that is frequently found in natural products, and its application to the total synthesis of the natural cardiotonic steroids oleandrin and beaumontoside. To improve the reaction diastereoselectivity and to minimize side-product formation, an extensive evaluation and optimization of the conditions leading to alpha-selective glycosylation of digitoxigenin with l-oleandrose-based donors was conducted. These studies led to the exploration of 8 different phosphine.acid complexes or salts and yielded HBr.PPh(3) as the optimal catalyst, which provided in the cleanest alpha-glycosylation and produced protected beaumontoside in 67% yield. Subsequent application of these conditions to synthetic Oleandrigenin afforded the desired alpha-product in 69% isolated yield horizontal line enabling the completion of the first synthesis of oleandrin in 17 steps (1.2% yield) from testosterone.

Antitumour effect of odoroside A and its derivative on human leukaemia cells through the ROS/JNK pathway.[Pubmed:34634178]

Basic Clin Pharmacol Toxicol. 2022 Jan;130(1):56-69.

Oleandrigenin-3-O-beta-D-diginoside (a derivative of odoroside A), isolated and purified by our group, has seldom been explored for its pharmacological activity. This study aimed at clarifying the mechanisms towards the leukaemia-suppressive role of odoroside A (compound #1) and its derivative, Oleandrigenin-3-O-beta-D-diginoside (compound #2) isolated from Nerium oleander. Viability and nuclear morphology change were assessed by CCK-8 assay and fluorescence microscope, respectively. Then, the cell apoptosis and autophagy induced by the compounds were detected by flow cytometry and Western blot. Xenograft model of nude mice was also applied to measure the leukaemia-suppressive effects of compound #2 in vivo. The result displayed that compound #1 and compound #2 inhibited the proliferation of HL60 and K562 cells and stronger effects were found in HL60 than K562 cells. Both of the compounds induced a dose-dependent apoptosis and autophagy in HL60 cells, where compound #2 was more potent than compound #1. Compound #2 also demonstrated a time-dependent apoptosis and autophagy in HL60 cells. Furthermore, ROS generation and JNK phosphorylation occurred in a dose-dependent manner in the cells treated with compound #2. Mitochondria also played critical role, proved by the decrease of Bcl-2, the release of cyto c to cytosol and the activation of caspase-3 and caspase-9. Moreover, the antitumour effects of compound #2 were validated in the nude mouse xenograft model in vivo. Odoroside A and its derivative inhibited the growth of leukaemia by inducing apoptosis and autophagy through the activation of ROS/JNK pathway. These results suggest that the compounds can serve as potential antitumour agents against leukaemia, especially acute myeloid leukaemia (AML).

Synthesis of Cardiotonic Steroids Oleandrigenin and Rhodexin B.[Pubmed:34255963]

J Org Chem. 2021 Aug 6;86(15):10249-10262.

This article describes a concise synthesis of cardiotonic steroids Oleandrigenin (7) and its subsequent elaboration into the natural product rhodexin B (2) from the readily available intermediate (8) that could be derived from the commercially available steroids testosterone or DHEA via three-step sequences. These studies feature an expedient installation of the beta16-oxidation based on beta14-hydroxyl-directed epoxidation and subsequent epoxide rearrangement. The following singlet oxygen oxidation of the C17 furan moiety provides access to Oleandrigenin (7) in 12 steps (LLS) and a 3.1% overall yield from 8. The synthetic Oleandrigenin (7) was successfully glycosylated with l-rhamnopyranoside-based donor 28 using a Pd(II)-catalyst, and the subsequent deprotection under acidic conditions provided cytotoxic natural product rhodexin B (2) in a 66% yield (two steps).

Structural Analysis of Diastereomeric Cardiac Glycosides and Their Genins Using Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry.[Pubmed:33818079]

J Am Soc Mass Spectrom. 2021 May 5;32(5):1205-1214.

Ultraperformance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) is an economical and indispensable tool in natural product research to investigate novel metabolites, biomarker discovery, chemical diversity exploration, and structure elucidation. In this study, the structural analysis of 38 naturally occurring cardiac glycosides (CGs) in various tissues of Nerium oleander was achieved by the extensive use of mass spectrometry. The chemical diversity of CGs was described on the basis of characteristic MS/MS fragmentation patterns, accurate mass measurement, and published scientific information on CGs from Nerium oleander. It was observed that only six genins, viz., Delta(16)anhydrogitoxigenin, Delta(16)adynerigenin, gitoxigenin, Oleandrigenin, digitoxigenin, and adynerigenine, produce 38 diverse chemical structures of CGs. Among them, 20 were identified as diastereomers having a difference in a sugar (l-oleandrose, beta-d-diginose, and beta-d-sarmentose) unit. However, the differentiation of diastereomeric CGs was not possible by only MS/MS fragments. Thus, the diastereomer's chromatographic elution order was assigned on the basis of the relative retention time (RRt) of two reference standards (odoroside A and oleandrin) among their diastereomers. Besides this, the in-source fragmentation of CGs and the MS/MS of m/z 325 and 323 disaccharide daughter ions also exposed the intrinsic structure information on the sugar units. The daughter ions m/z 162, 145, 113, 95, and 85 in MS/MS spectra indicated the abundance of l-oleandrose, beta-d-diginose, and beta-d-sarmentose sugars. At the same time, m/z 161, 143, 129, and 87 product ions confirmed the presence of a beta-d-digitalose unit. As a result, the UPLC-ESI/TQD system was successfully utilized for the structure characterization of CGs in Nerium oleander tissues.

Fatal poisoning by ingestion of a self-prepared oleander leaf infusion.[Pubmed:33237522]

Forensic Sci Med Pathol. 2021 Mar;17(1):120-125.

An unusual case of poisoning by the ingestion of oleander leaves is reported. A 71 year old male laboratory technician committed suicide at home in this unusual manner. At the death scene a steel pan and other paraphernalia, used for the extraction of oleandrin and other cardiac glycosides from the leaves of the Nerium oleander plant were found.Toxicological investigations for oleandrin, Oleandrigenin, neritaloside, and odoroside were performed by LC-MS/MS on all biological samples (peripheral blood, vitreous humor, urine, liver, gastric contents) and on the yellow infusion found at the death scene.In all samples, toxic levels of oleandrin were detected (blood 37.5 ng/mL, vitreous humor 12.6 ng/mL, urine 83.8 ng/mL, liver 205 ng/mg, gastric content 31.2 microg/mL, infusion 38.5 microg/mL). Qualitative results for Oleandrigenin, neritaloside, and odoroside were obtained. Oleandrigenin was present in all tissue samples whereas neritaloside and odoroside were absent in the blood and vitreous humor but present in urine, liver, gastric content, and in the leaf brew.The purpose of this study was the identification of oleandrin and its congener Oleandrigenin, detected in the vitreous humor. The blood/vitreous humor ratio was also calculated in order to assess of the likely time interval from ingestion to death. According to the toxicological results death was attributed to fatal arrhythmia due to oleander intoxication. The manner of death was classified as suicide through the ingestion of the infusion.

Synthesis and evaluation of Na(+)/K(+)-ATP-ase inhibiting and cytotoxic in vitro activities of oleandrigenin and its selected 17beta-(butenolidyl)- and 17beta-(3-furyl)- analogues.[Pubmed:32645647]

Eur J Med Chem. 2020 Sep 15;202:112520.

Natural cardiac-active principles built upon the 14,16beta-dihydroxy-5beta,14beta-androstane core and bearing a heterocyclic substituent at 17beta, in particular, a cardenolide - oleandrin and a bufadienolide - bufotalin, are receiving a great deal of attention as potential anticancer drugs. The densely substituted and sterically shielded ring D is the particular structural feature of these compounds. The first synthesis of Oleandrigenin from easily available steroid starting material is reported here. Furthermore, selected 17beta-(4-butenolidyl)- and 17beta-(3-furyl)-14,16beta-dihydroxy-androstane derivatives were en route synthesized and examined for their Na(+)/K(+)-ATP-ase inhibitory properties as well as cytotoxic activities in normal and cancer cell lines. It was found that the furyl-analogue of Oleandrigenin/bufatalin (7) and some related 17-(3-furyl)- derivatives (19, 21) show remarkably high Na(+)/K(+)-ATP-ase inhibitory activity as well as significant cytotoxicity in vitro. In addition, Oleandrigenin 2 compared to derivatives 21 and 25 induced strong apoptosis in human cervical carcinoma HeLa cells after 24 h of treatment.

Anvirzel(TM)regulates cell death through inhibiting GSK-3 activity in human U87 glioma cells.[Pubmed:31900072]

Neurol Res. 2020 Jan;42(1):68-75.

Objectives: Cardiac glycosides are used as potential anti-cancer agents due to their effects on the inhibition of proliferation and induction of apoptosis and/or autophagy in cancer cells. Herein, we aimed to study the potential signaling pathways taken role in differential cell-death properties of Anvirzel(TM) which is consisted of two toxic cardiac glycosides (oleandrin and Oleandrigenin), in U87 human glioblastoma cells.Methods: The anti-proliferative and anti-migratory effects of Anvirzel(TM) were assessed in U87 cells by WST-1 assay and wound healing assay, respectively. After treatment of Anvirzel(TM)with doses of 10, 25, 50, 100 and 250 mug/ml, expression levels of proteins related to cell death were investigated by Western blot.Results: Anvirzel markedly inhibited the growth of U87 cells in a time- and dose-dependent manner following 24 h and 48 h treatments (p < 0.05). In addition, it was found that Anvirzel inhibited GSK-3, NOS and HIF1-alpha expressions whereas activated ERK in U87 cells compared to vehicle (p < 0.05).Discussion: The results suggested that Anvirzel(TM) regulated cell death distinctly from apoptosis in human glioblastoma cells. Further studies are required for validation of mechanistic insights about the potential signaling pathways taken role in differential cell death properties of Anvirzel(TM).

Synthesis and evaluation of cytotoxic and Na(+)/K(+)-ATP-ase inhibitory activity of selected 5alpha-oleandrigenin derivatives.[Pubmed:31325787]

Eur J Med Chem. 2019 Oct 15;180:417-429.

Oleandrin, the major biologically active constituent of shrub Nerium oleander preparations of which have been used in traditional Mediterranean and Asian medicine, attracts a great deal of attention due to its pronounced anticancer activity. The synthesis of Oleandrigenin model, 16beta-hydroxy-3beta-methoxy-5alpha-card-20(22)-enolide 16-acetate, from androstenolone acetate through 17beta-(3-furyl)-intermediates has been developed. Several related 17beta-(butenolidyl)- and 17beta-(furyl)-androstane derivatives were synthesized and tested for in vitro cytotoxic and Na(+)/K(+)-ATP-ase inhibitory activities. Comparison of Na(+)/K(+)-ATP-ase inhibitory and cytotoxic activity underlines complex nature of the relationship.

Cytotoxic Cardiac Glycoside Constituents of Vallaris glabra Leaves.[Pubmed:29072457]

J Nat Prod. 2017 Nov 22;80(11):2987-2996.

Thirteen cardenolide glycosides (1-13) were isolated from the CH(2)Cl(2) and MeOH extracts of Vallaris glabra leaves. The structures of the new compounds (2-13) were identified by spectroscopic methods, with the absolute configurations of the sugar moieties determined by acid hydrolysis. All compounds were evaluated for their cytotoxic activity against human cervix adenocarcinoma, lung carcinoma, and colorectal adenocarcinoma cell lines. The two most potent compounds [2'-O-acetylacoschimperoside P (1) and Oleandrigenin-3-O-alpha-l-2'-O-acetylvallaropyranoside (2)] exhibited IC(50) values in the range of 0.03-0.07 muM.

In vitro anti-influenza virus activity of a cardiotonic glycoside from Adenium obesum (Forssk.).[Pubmed:21899996]

Phytomedicine. 2012 Jan 15;19(2):111-4.

Methanolic extracts of six Saudi plants were screened for their in vitro antiviral activity using influenza virus A/PR/8/34 (H1N1) and MDCK cells in an MTT assay. The results indicated that the extracts of Adeniumobesum and Tephorosianubica possessed antiviral activity (99.3 and 93.3% inhibition at the concentration of 10 mug/ml, respectively). Based on these results A. obesum was selected for further study by applying bioactivity-guided fractionation to isolate its antiviral principle. The antiviral principle was isolated from the chloroform fraction through solvent fractionation, combined open liquid chromatography and HPLC. The isolated active compound A was identified as Oleandrigenin-beta-D-glucosyl (1-->4)-beta-D-digitalose, on the basis of its spectral analysis (MS, 1D and 2D NMR). The isolated glycoside showed reduction of virus titre by 69.3% inhibition at concentration of 1 mug/ml (IC(50)=0.86 mug/ml).

Cardiac glycosides from shoot cultures of Cryptostegia grandiflora.[Pubmed:21808532]

Pharmacognosy Res. 2010 Jan;2(1):15-8.

Cardiac glycosides in shoot cultures of Cryptostegia grandiflora were identified when grown in modified MS medium. The change in shoot segments and cardiac glycosides content was followed between day zero and day 12 at 2-day intervals. The content of cardiac glycosides in leaves and shoot cultures of Cryptostegia grandiflora was monitored by HPLC. Two major compounds were detected and isolated from shoot cultures extract, named Oleandrigenin 3-O-beta - glucopyranosyl-(1-->4) - beta-cymaropyranosyl-(1-->4)-beta-digitoxopyranoside (cryptostigmin I) and Oleandrigenin 3-O-beta - glucopyranosyl-(1-->4)-alpha-rhamnopyranoside (cryptostigmin II). The structures of the isolated compounds were verified by means of MS and NMR spectral analysis, as well as by comparison with authentic samples. The leaves and shoot cultures were analyzed for their cardiac glycosides content. The shoot cultures inoculated into MS-based culture media supplemented with 0.1 mg L(-1) BA, 30 g L(-1) sucrose, 0.1 g L(-1)myo-inositol and 0.1 g L(-1) ascorbic acid were found to contain a quantity of cardiac glycosides that was about four fold the cardiac glycosides content of leaves extract.

In vitro study of the effectiveness of three commercial adsorbents for binding oleander toxins.[Pubmed:19274509]

Clin Toxicol (Phila). 2009 Mar;47(3):213-8.

INTRODUCTION: Oleander (Nerium oleander) poisoning is a common problem found in many parts of the world. The oleander toxicity is due to oleandrin and its aglycone metabolite Oleandrigenin. Activated charcoal is a useful gastrointestinal decontamination agent that limits the absorption of ingested toxins. A relatively new clay product, Bio-Sponge, containing di-tri-octahedral smectite as the active ingredient, is also recommended for adsorbing bacterial toxins in the gastrointestinal tract. Bio-Sponge has been used to prevent gastrointestinal absorption of oleander toxins in livestock but the efficacy of activated charcoal and Bio-Sponge for adsorbing oleandrin and Oleandrigenin has not yet been studied. METHODS: An in vitro experiment to compare the efficacy of three commercially available adsorbents was performed. The adsorbents include Bio-Sponge, ToxiBan granules, and a generic grade activated charcoal. RESULTS: ToxiBan granules have the highest adsorptive capacity, followed by the generic grade activated charcoal, and finally, Bio-Sponge. DISCUSSION: Bio-Sponge did not adsorb oleandrin and Oleandrigenin at concentrations that are expected to be present in the gastrointestinal tract of poisoned animals. CONCLUSIONS: On the basis of this in vitro study, products containing activated charcoal are more effective for binding oleander toxins and providing gastrointestinal decontamination than products containing di-tri-octahedral smectite. However, the ability of these adsorbents to alter the clinical outcome in oleander-poisoned animals or humans is yet to be evaluated.

Unexpectedly dangerous escargot stew: oleandrin poisoning through the alimentary chain.[Pubmed:17137529]

J Anal Toxicol. 2006 Nov-Dec;30(9):683-6.

A female, aged 43 and a male, aged 66, experienced gastrointestinal and cardiovascular symptoms after a meal including snail stew. Twelve hours after the ingestion, they presented with nausea, vomiting, diarrhea, and cardiovascular symptoms typical of acute toxic digoxin ingestion and were hospitalized. The man's electrocardiogram was altered, and the woman's was normal. Serum digoxin levels, measured on a Roche COBAS Integra 800 with the Roche On-Line Digoxin reagent, were 1.14 and 1.00 nmol/L, respectively. Potassium levels were normal in both patients. The serum digoxin concentration decreased on the second day, and symptoms resolved on the third day with patients fully recovered (i.e., reversion to a normal sinus rhythm). Cardiac-glycoside-like intoxication symptoms follow the ingestion of leaves or flowers of Nerium oleander. The consumed snails were suspected to be responsible for the intoxication. In the homogenized snail tissue, the concentration expressed in digoxin equivalents was 0.282 nmol/g. The presence of oleandrin and Oleandrigenin in the snails was confirmed by liquid chromatography-tandem mass spectrometry analysis, which was performed on a ionic-trap Finnigan LXQ instrument using an electrospray ionization interface. High-pressure liquid chromatographic separation was performed on a C18 column with a gradient of methanol/water. An extract of oleander leaves was used as reference.

Activated charcoal is effective but equilibrium dialysis is ineffective in removing oleander leaf extract and oleandrin from human serum: monitoring the effect by measuring apparent digoxin concentration.[Pubmed:12766561]

Ther Drug Monit. 2003 Jun;25(3):323-30.

Accidental poisoning from oleander leaf or oleander tea can be life threatening. The authors studied the effectiveness of activated charcoal and equilibrium dialysis in removing oleander leaf extract and commercially available oleandrin as well as Oleandrigenin, the active components of oleander plant, from human serum. Oleander leaf extract was prepared in distilled water and drug-free serum was supplemented with the extract. Then serum was treated with activated charcoal at room temperature and an aliquot was removed at 0 minutes, 10 minutes, 20 minutes, and finally 30 minutes to study the presence of oleander extract by measuring the apparent digoxin concentration using the FPIA for digoxin. The authors observed effective removal of oleander extract by activated charcoal. When the authors supplemented other drug-free serum pools with pure oleandrin or Oleandrigenin and then subsequently treated them with activated charcoal, the authors observed complete removal of digoxin-like immunoreactivity at the end of 30 minutes' treatment. When drug-free serum pool supplemented with either oleander leaf extract, oleandrin, or Oleandrigenin was passed through a small column packed with activated charcoal, the authors observed almost no apparent digoxin concentration following the passage through the column indicating that activated charcoal is very effective in removing oleander from human serum in vitro. In contrast, when serum pools containing either oleander leaf extract or oleandrin were subjected to equilibrium dialysis against phosphate buffer at pH 7.4, the authors observed no significant reduction in apparent digoxin concentration even after 24 hours. The authors conclude that activated charcoal is effective but equilibrium dialysis is ineffective in removing oleander leaf extract from human serum.