bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transformation of Azadiradione to Nimbocinol and 17β‐Hydroxynimbocinol, and StructurePesticidal‐Activity Relationship of Triterpenoids isolated from Azadirachta indica A. Juss. (Neem)
Authors: Siddiqui Bina S. , Rasheed Munawwer , Faizi Shaheen , Firdous  , Ali S. Tariq , Tariq Rajput M. , Naqvi Syed Naeem‐ul‐Hassan 
Published: June 2004

AbstractDuring studies on the structurepesticidal‐activity relationship of Azadirachta indica constituents, azadiradione (1) was treated with methanolic K2CO3 to obtain 7‐deacetyl derivative nimbocinol (2). Unexpectedly, 17β‐hydroxynimbocinol (3), reported earlier as a natural product, was also formed. The structurepesticidal‐activity relationship of triterpenoids 1–16 against Anopheles stephensi Liston is described towards understanding the active functionalities responsible for the pesticidal activity of triterpenoids having apoeuphane(apotirucallane) and gedunin skeleta. The pesticidal activities of triterpenoids 2–8 are reported for the first time.
Isoflavonoid Glycosides from the Rhizomes of Iris germanica
Authors: Atta‐ur‐Rahman  , Nasim Shama , Baig Irfan , Orhan Ilkay , Sener Bilge , Ayanoglu Filiz , Choudhary M. Iqbal 
Published: June 2004

AbstractFive new di‐ and triglycosides, irigenin 7‐[O‐β‐D‐glucopyranosyl‐(1→6)‐β‐D‐glucopyranoside] (1), 6‐hydroxygenistein 4′‐[O‐β‐D‐glucopyranosyl‐(1→6)‐β‐D‐glucopyranoside] (2), nigricin 4′‐[O‐β‐D‐glucopyanosyl‐(1→6)‐β‐D‐glucopyranoside] (3), nigricin 4′‐[O‐β‐D‐glucopyanosyl‐(1→2)‐O‐[α‐L‐rhamnopyranosyl‐(1→6)]‐β‐D‐glucopyranoside] (4), and 7‐{4′‐{[2″‐O‐(4′′′′‐acetyl‐2′′′′‐methoxyphenyl)‐β‐D‐glucopyranosyl]oxy}‐3′‐(β‐D‐glucopyranosyloxy)phenyl]‐9‐methoxy‐8H‐1,3‐dioxolo[4,5‐g]‐[1 benzopyran‐8‐one‐] (5), along with a known compound, nigricin 4′‐(β‐D‐glucopyranoside) (6), were isolated from the rhizomes of Iris germanica. The structures of these compounds were established by spectroscopic methods, including 2D NMR spectroscopic techniques.
Photophysical and Photochemical Studies of Pyridoxamine
Authors: Bueno Claudio , Encinas María Victoria 
Published: June 2004

AbstractThe absorption and fluorescence emission of pyridoxamine were studied as function of pH and solvent properties. In the ground state, pyridoxamine exhibits different protonated forms in the range of pH 1.5–12. Fluorescence studies showed that the same species exist at the lowest singlet excited state but at different pH ranges. The phenol group is by ca. 8 units more acidic in the excited state than in the ground state. On the other hand, the pyridine N‐atom is slightly more basic in the lowest excited state than in the ground state. Excitation spectra and emission decays in the pH range of 8–10 indicate the protonation of the pyridine N‐atom by proton transfer from the amine group, in the ground and singlet excited states. Spectroscopic studies in different solvents showed that pyridoxamine in the ground or excited states exhibits intramolecular proton transfer from the pyridine N‐atom to the phenol group, which is more favorable in solvents of low hydrogen‐bonding capacity. The cationic form with the protonated phenolic group, which emits at shorter wavelength, is the dominant species in nonprotic solvents, but, in strong proton‐donor solvents, both forms exist. The fluorescence spectra of these species exhibit blue shift in protic solvents. These shifts are well‐correlated with the polarity and the H‐donor ability of the solvent.
Cyclopeptides and Amides from Pseudostellaria heterophylla (Caryophyllaceae)
Authors: Yang Ya‐bin , Tan Ning‐hua , Zhang Fei , Lu Ya‐qing , He Min , Zhou Jun 
Published: June 2004

AbstractFrom the roots of Pseudostellaria heterophylla, three cyclopeptides and three amides were isolated, besides heterophyllin A and B. Their structures were determined as cyclo (Ala‐Gly‐Pro‐Val‐Tyr‐) (heterophyllin J; 1), cyclo (Ala‐Gly‐Pro‐Tyr‐Leu‐) (pseudostellarin A; 2), cyclo (Gly‐Gly‐Gly‐Pro‐Pro‐Phe‐Gly‐Ile‐) (pseudostellarin B; 3), methyl γ‐hydroxypyroglutamate (4), methyl pyroglutamate (5), and pyroglutamic acid (6) on the basis of spectral data, especially 2D‐NMR data. Among them, compounds 1 and 4 are new compounds.
Isolation, Structure, and HIV‐1 Integrase Inhibitory Activity of Xanthoviridicatin E and F, Two Novel Fungal Metabolites Produced by Penicillium chrysogenum
Authors: Singh Sheo B. , Zink Deborah L. , Guan Ziqiang , Collado Javier , Pelaez Fernando , Felock Peter J. , Hazuda Daria J. 
Published: June 2004

AbstractHIV‐1 Integrase is a critical enzyme for replication of HIV, and its inhibition is one of the most promising new drug targets for anti‐retroviral therapy with potentially significant advantages over existing therapies. Xanthoviridicatins E (1) and F (2) are two novel polyketide natural products that were isolated from a fermentation broth of an endophytic strain of Penicillium chrysogenum isolated from the living leaves collected in Peru. These compounds are new members of the unsymmetrical xanthoviridicatin family represented by the broader xanthomegnin family. Xanthoviridicatins E and F inhibited the cleavage reaction of HIV‐1 integrase with an IC50 of 6 and 5 μM, respectively. The bioassay‐directed isolation, structure elucidation, and HIV‐1 inhibitory activity of these compounds are described.
Isolation and Structure Determination of New Jatrophane Diterpenoids from Euphorbia platyphyllos L.
Authors: Hohmann Judit , Forgo Peter , Csupor Dezsö , Schlosser Gitta 
Published: June 2004

AbstractThree new, highly functionalized jatrophane diterpenes (1–3) have been isolated from the whole, dried plants of Euphorbia platyphyllos L., together with one known jatrophane polyester (4). The structures were established by UV/VIS spectroscopy, HR‐ESI‐MS, and advanced two‐dimensional NMR, including 1H‐NMR, JMOD, 1H,1H‐COSY, HMQC, and HMBC experiments. Stereochemical studies and conformational analyses were performed by means of NOESY experiments. Interestingly, compounds 1–4 do not represent a stereochemically uniform series because they differ in the orientations of the Me groups at C(2), C(6), and C(13). A similar observation was reported earlier for Euphorbia serrulata, whose diterpenes are related to the compounds obtained from E. platyphyllos. This chemical relationship is of taxonomic importance and supports the botanical similarity of the two species.
A New Dimeric Stilbenoid with a Five‐Membered Lactone Ring from Shorea hemsleyana
Authors: Ito Tetsuro , Tanaka Toshiyuki , Iinuma Munekazu , Nakaya Ken‐ichi , Takahasi Yoshikazu , Nakamura Hikaru , Naganawa Hiroshi , Riswan Soedarsono 
Published: June 2004

AbstractFrom the stem bark of Shorea hemsleyana, a new dimeric stilbenoid with a five‐membered lactone ring, shorealactone (1) was isolated. The absolute configuration was determined by means of 2D NMR techniques and X‐ray crystal‐structure analysis of its 4‐bromobenzoyl derivative 1e by means of anomalous scattering of the Br‐atom.
Anionically Substituted 1,1′,1″‐Methylidynetris[1H‐pyrazole] Ligands for the Formation of Neutral Lanthanide Complexes in Water: Synthesis, Characterization, and Photophysical Properties
Authors: Charbonnière Loïc J. , Ziessel Raymond 
Published: June 2004

AbstractThe six‐step synthesis of the new podand‐type ligand 6,6′,6″‐[methylidenetri(1H‐pyrazole‐1,3‐diyl)]tris[pyridine‐2‐carboxylic acid] (LH3) is described. Reaction of LH3 with LnCl3 ⋅6 H2O (Ln=Eu, Gd, Tb) in MeOH resulted in the isolation of [LnL]⋅HCl complexes characterized by elemental analysis, mass and IR spectroscopy. Photophysical studies of the Eu and Tb complexes in aqueous solutions revealed the characteristic luminescence features of the metal atoms, indicative of an efficient ligand‐to‐metal energy‐transfer process. Determination of the luminescence quantum yields in H2O showed the Tb complex to be highly luminescent (ϕ=15%), while, for the Eu complex, the quantum efficiency was only 2%. Excited‐state‐lifetime measurements in H2O and D2O evidenced the presence of ca. three H2O molecules in the first coordination sphere of the complexes. Investigation of the Gd complex allowed the determination of the ligand‐centered triplet state and showed the ligand to be well suited for energy transfer to the metal. The luminescence properties of the complexes are described, and the properties of the ligand as a suitable complexation pocket is questioned.
Cyclotrimerization of Benzobarrelene: Synthesis of New Isomeric Barrelene Architectures
Authors: Daştan Arif , Fabris Fabrizio , De Lucchi Ottorino , Güney Murat , Balcı Metin 
Published: June 2004

AbstractThe cyclotrimerization reaction of benzobarrelene derivatives was investigated. Dibromobenzobarrelene 10 was converted to the bromostannyl derivative 11, which was used as the substrate of the cyclotrimerization reaction. Thus, reaction of 11, with copper(I) thiophene‐2‐carboxylate (CuTC) gave a mixture of the isomeric cyclotrimers 5 and 6 and the dimers 12 and 13, in addition to a trace of protodestannylated bromoalkene 14 (Scheme 2).
Self‐Assembly of Non‐Biological Polymeric Strands Undergoing Enforced Helical Self‐Organization
Authors: Schmitt Jean‐Louis , Lehn Jean‐Marie 
Published: June 2004

AbstractThe polycondensation of a dihydrazino‐pyrimidine (5 and 6) with a pyrimidine‐dicarbaldehyde (7 and 8b) provides an efficent access to helical polymeric strands based on the formation of hydrazone connections between the pyrimidine groups. The folding into a helical structure is enforced by the helicity codon defined by the (hydrazonepyrimidine) sequence. The polymers obtained have been characterized by mass spectrometry, indicating molecular weights up to ca. 12000 Da. Electronic spectra display specific absorption and emission features. These helical polymers present a core diameter of ca. 20 Å, a pitch of 3.5 Å, and, for a molecular weight around 9000 Da, a height of ca. 42 Å with 12 turns. The self‐assembled helical polymers obtained represent stable frameworks for the lateral attachment of functional residues in a helical disposition. Such entities may possess a range of novel chemical as well as biological properties.
Structure Elucidation of the First Inhibitors of Human Papillomavirus Type 11 E1E2 ProteinProtein Interaction
Authors: Yoakim Christiane , Goudreau Nathalie , McGibbon Graham A. , O'Meara Jeff , White Peter W. , Ogilvie William W. 
Published: June 2004

AbstractA novel series of inhibitors of the HPV11 E1E2 proteinprotein interaction was identified. These inhibitors, which were discovered as a result of high‐throughput screening, feature an indandione system spiro‐fused onto an appropriately substituted tetrahydrofuran ring. Early stability studies indicated, surprisingly, that this particular series of compounds were readily converted, in binding assay buffer, to the corresponding carboxylates. NMR and mass spectrometry techniques were used to elucidate the structures of these products and the mechanism by which they are produced.
3β‐(Stearyloxy)olean‐12‐ene from Austroplenckia populnea: Structure Elucidation by 2D‐NMR and Quantitative 13C‐NMR Spectroscopy
Authors: Filho S. A. Vieira , Duarte L. P. , Silva G. D. F. , Howarth O. W. , Lula I. S. 
Published: June 2004

Abstract3β‐(Stearyloxy)olean‐12‐ene was isolated from a hexane extract of Austroplenckia populnea Reiss (Celastraceae) leaves. The structure was solved by means of quantitative 13C‐NMR, HMBC, HMQC, COSY, NOESY, and NOE difference spectra. The mass spectrum showed an [M+1]+ ion peak at m/z 693, and the molecular formula C48H84O2 was confirmed by combustion analysis.
Microbial Transformation of Isolongifolen‐4‐one
Authors: Choudhary M. Iqbal , Musharraf Syed Ghulam , Khan Mahmud Tareq Hassan , Abdelrahman Doaa , Parvez Massod , Shaheen Farzana , Atta‐ur‐Rahman  
Published: June 2004

AbstractThe microbial transformation of (+)‐isolongifolen‐4‐one (4) by a number of fungi by means of a standard two‐stage fermentation technique afforded (7R)‐12‐hydroxyisolongifolen‐4‐one (5), (7S)‐13‐hydroxyisolongifolen‐4‐one (6), (11R)‐11‐hydroxyisolongifolen‐4‐one (7), (10R)‐10‐hydroxyisolongifolen‐4‐one (8), and (9R)‐9‐hydroxyisolongifolen‐4‐one (9) (Scheme). All five metabolites were found to be new, and metabolites 6 and 9 showed potent tyrosinase inhibitory activity (Table 1). The metabolites and their derivatives were characterized on the basis of spectroscopic and single‐crystal X‐ray‐diffraction techniques.
Comparative Study on the Reactivity of 6‐Haloimidazo[1,2‐a]pyridine Derivatives towards Negishi‐ and Stille‐Coupling Reactions
Authors: Hervet Maud , Théry Isabelle , Gueiffier Alain , Enguehard‐Gueiffier Cécile 
Published: June 2004

AbstractThe scope of the Suzuki‐cross‐coupling reaction of 6‐haloimidazo[1,2‐a]pyridines is dependent on the availability of the (hetero)arylboronic acids. Thus, with the aim to develop expanded applications of (hetero)arylations of imidazo[1,2‐a]pyridines, we investigated the Negishi‐ and Stille‐cross‐coupling reactions at the 6‐position. Remarkably, attempts to apply the Negishi‐cross‐coupling conditions to the organozinc derivative prepared from 6‐haloimidazo[1,2‐a]pyridine via a lithiumzinc exchange led to the 5‐phenyl compound 3 in 54% yield instead of the desired 6‐phenyl isomer (Scheme 1). In contrast, various commercially available halogenated five‐ or six‐membered‐ring heterocycles were efficiently coupled to the 6‐(trialkylstannyl)imidazo[1,2‐a]pyridine under Stille conditions (Table 2).
Micranthin C, a Novel 13(12→11)abeo‐Abietanoid from Isodon lophanthoids var. micranthus
Authors: Zhao Ai‐Hua , Li Sheng‐Hong , Zhao Qin‐Shi , Lin Zhong‐Wen , Sun Han‐Dong , Lu Yang , Zhang Li‐Li , Zheng Qi‐Tai 
Published: June 2004

AbstractA novel 13(12→11)abeo‐abietane skeletal diterpenoid, micranthin C (1), was isolated from Isodon lophanthoids var. micranthus. Its structure was determined by various spectroscopic techniques and finally confirmed by single‐crystal X‐ray diffraction.
A Novel Oxime‐Derived Solid Support for the Synthesis of 3‐Phosphorylated Oligonucleotides
Authors: Langenegger Simon M. , Moesch Luzia , Natt François , Hall Jonathan , Häner Robert 
Published: June 2004

AbstractOligonucleotides containing terminal phosphate groups serve as useful intermediates for different applications in molecular and cell biology, as well as for diagnostic purposes. The chemical synthesis of these derivatives has been an important topic of oligonucleotide research. We report here a novel polystyrene‐based solid support bearing an α‐hydroxy oximate linker that allows the synthesis of 3′‐phosphorylated oligodeoxynucleotides as well as oligoribonucleotides in high quality. The formation of the phosphorylated oligonucleotides likely proceeds through an eliminative pathway with concurrent nitroso‐ene production.
Synthesis of C(2)‐Substituted manno‐Configured Tetrahydroimidazopyridines and Their Evaluation as Inhibitors of Snail β‐Mannosidase
Authors: Terinek Miroslav , Vasella Andrea 
Published: June 2004

AbstractIt was shown that retaining β‐glucosidases and galactosidases of families 1–3 feature a strong interaction between C(2)OH of the substrate and the catalytic nucleophile. An analogous interaction can hardly take place for retaining β‐mannosidases. A structureactivity comparison between the inhibition of the β‐glucosidase from Caldocellum saccharolyticum (family 1) and β‐glucosidase from sweet almonds by the gluco‐imidazoles 1–6, and the inhibition of snail β‐mannosidase by the corresponding manno‐imidazoles 8–13 does not show any significant difference, suggesting that also the mechanisms of action of these glycosidases do not differ significantly. For this comparison, we synthesized and tested the manno‐imidazoles 9–13, 28, 29, 32, 35, 40, 41, 43, 46, 47, and 50. Among these, the alkene 29 is the strongest known inhibitor of snail β‐mannosidase (Ki=6 nM, non‐competitive); the aniline 35 is the strongest competitive inhibitor (Ki=8 nM).
The Aldol Reaction of Allenolates with Aldehydes in the Presence of Magnesium Diiodide (MgI2) as Catalyst
Authors: Deng Guang‐Hui , Hu Hui , Wei Han‐Xun , Paré Paul W. 
Published: June 2004

AbstractStereoselective synthesis of (Z)‐α‐(hydroxyalkyl)‐β‐iodoacrylates (=(2Z)‐2‐(hydroxyalkyl)‐3‐iodoprop‐2‐enoates) was achieved in a one‐pot coupling reaction from methyl prop‐2‐ynoate, Me3SiI, and an alkanal under mild conditions with MgI2 as catalyst (→ 1–9; see Table and Scheme 1). Baylis‐Hillman β‐iodo adducts were generated in excellent yields with high (Z)‐selectivity. The conversion of methyl prop‐2‐ynoate to an active methyl 3‐iodo‐1‐[(trimethylsilyl)oxy]allenolate intermediate in situ followed by carbonyl addition is proposed as the reaction sequence (Schemes 1 and 2).
Solid‐Phase Synthesis of Dipeptide‐Conjugated Nucleosides and Their Interaction with RNA
Authors: Dong Guimin , Zhang Liangren , Zhang Lihe 
Published: June 2004

AbstractDipeptide‐conjugated nucleosides were efficiently synthesized from the intermediates of 3′‐amino‐3′‐deoxy‐nucleosides by using the solid‐phase synthetic strategy with HOBt/HBTU (1‐hydroxy‐1H‐benzotriazole/2‐(1H‐benzotriazol‐1‐yl)‐1,1,3,3‐tetramethyluronium hexafluoroborate) as the coupling reagents (Schemes 1–3). CD Spectra and thermal melting studies showed that the synthesized hydrophobic dipeptidethymidine and uridine derivatives 8a–8d, 13a–d, and 18 had a mild affinity with the polyA⋅polyU duplex and could induce the change of RNA conformation. The results also implied that the interaction of conjugates with RNA might be related to the sugar pucker conformation of the nucleoside.
Recombinant single‐chain antibody fusion construct targeting human melanoma cells and containing tumor necrosis factor
Authors: Liu Yuying , Cheung Lawrence H. , Marks John W. , Rosenblum Michael G. 
Published: June 2004

AbstractFusion constructs targeting tumor cells have significant potential applications against both solid tumors and hematologic malignancies. We developed a fusion construct of tumor necrosis factor (TNF) and a single‐chain antibody (scFvMEL) recognizing the gp240 antigen on human melanoma cells. The scFvMEL/TNF construct, like TNF itself, was found to exist in solution primarily as a trimer of 45 kDa monomers (trimeric molecular weight = 135 kDa). The fusion construct bound specifically to gp240 antigen‐positive but not to antigen‐negative cells. The TNF component of the construct was biologically active (specific activity = 1 × 107 U/mg) compared with free TNF (specific activity = 2.6 × 107 U/mg) and was more cytotoxic to antigen‐positive A375‐M melanoma cells (IC50 = 100 pM) than TNF alone (IC50 = 1,000 pM) and, additionally, was active against AAB‐527 melanoma cells (IC50 = 20 nM) resistant to TNF itself (IC50 > 1,000 nM). The augmented cytotoxicity was mediated by antibody‐specific binding to the cell surface. Both A375‐M and AAB‐527 cells were shown to express TNFR1 and TNFR2 on the cell surface. The TNF moiety of the fusion construct was efficiently delivered into cells in time‐dependent increase in cytosol as assessed by immunofluorescent staining of human melanoma cells. Radiolabeled scFvMEL/TNF localized effectively in human melanoma xenografts in nude (nu/nu) mice with a tumor:blood ratio of approximately 8 at 72 hr after administration. Our studies suggest that because of its unique biologic activity and low antigenic potential, scFvMEL/TNF makes an excellent cytotoxic protein for potential clinical treatment of human melanoma. © 2003 Wiley‐Liss, Inc.
Modification effects of GSTM1, GSTT1 and CYP2E1 polymorphisms on associations between raw salted food and incomplete intestinal metaplasia in a high‐risk area of stomach cancer
Authors: Chen Shu‐Yuan , Liu Tzeng‐Ying , Shun Chia‐Tung , Wu Ming‐Shiang , Lu Tsung‐Hsueh , Lin Jaw‐Town , Sheu Jin‐Chuan , Santella Regina M. , Chen Chien‐Jen 
Published: June 2004

AbstractIncomplete intestinal metaplasia (IM) is a precursor of stomach cancer. To identify risk factors of incomplete IM, a 2‐stage survey was carried out in 1995 among 1,485 residents in Matzu, an area with highest mortality from stomach cancer in Taiwan. There were 312 study subjects including 174 men and 138 women sampled for the gastroendoscopic examination of IM. Information on personal and familial history of stomach cancer, cigarette smoking, alcohol consumption and intake frequency of various salted food items were obtained by personal interview based on a structured questionnaire. Blood samples were collected from each participant. Four biopsies per subject were taken from all subjects at gastroendoscopic examination to diagnose the status of IM pathologically. The Helicobacter pylori in biopsies was detected by the histomorphological or immunochemistry method, and antibodies against H. pylori in serum by the enzyme‐linked immunosorbent assay. Plasma level of selenium was determined by atomic absorption spectrometry, plasma level of retinol, α‐tocopherol, α‐carotene, and β‐carotene by high performance liquid chromatography, genotypes of glutathione S‐transferase (GST) M1 and T1 and cytochrome P450 (CYP) 2E1 by polymerase chain reaction. The significant association between history of stomach cancer among first‐degree relatives and incomplete IM was found (odds ratio [OR] = 2.50; 95% confidence interval [CI] = 1.15–5.43). There was no association between H. pylori infection and incomplete IM. Alcohol drinkers for >20 years had an elevated risk compared to non‐drinkers (OR = 3.34; 95% CI = 1.19–9.39). No associations between incomplete IM and plasma levels of selenium, retinol, α‐tocopherol, α‐carotene and β‐carotene were found. Salted food including salted meat, dehydrated salted vegetables and raw salted seafood consumed at ages of ≤15 and 16–30 years old was associated with an increased IM risk with OR ranging from 2–3. More striking associations between incomplete IM and salted food intake were observed among subjects with genotypes of GSTM1 null, GSTT1 non‐null and CYP2E1 c1/c1. Our study suggests the importance of gene–environment interaction on the development of incomplete IM. © 2003 Wiley‐Liss, Inc.
2‐methoxyestradiol induces caspase‐independent, mitochondria‐centered apoptosis in DS‐sarcoma cells
Authors: Lambert Christine , Apel Katrin , Biesalski Hans Konrad , Frank Juergen 
Published: June 2004

AbstractThe anti‐cancer potential of the natural estrogen metabolite 2‐methoxyestradiol is associated with microtubuli interaction, anti‐angiogenetic effects and inhibition of superoxide dismutase leading to apoptosis. The effectors of apoptotic signaling through 2‐methoxyestradiol, however, are cell type‐dependent. We investigated the effect of 2‐methoxyestradiol on several events associated with apoptosis in rat DS‐sarcoma cells. Translocation of the pro‐apoptotic protein Bax to mitochondria was identified as an initial apoptotic event that was accompanied by a decrease in mitochondrial transmembrane potential and the formation of reactive oxygen species (ROS) followed by mitochondrial release of apoptosis inducing factor and endonuclease G. In addition, 2‐methoxyestradiol treatment caused upregulation of death receptor ligands FasL and TNFα and induced caspase‐8 activation. The pan caspase inhibitor Z‐VAD‐FMK did not suppress apoptotic cell death, however, indicating that the major pro‐apoptotic effect of 2‐methoxyestradiol is mediated by a caspase‐independent mechanism. Furthermore, ROS do not seem to play a pivotal role in the toxic/apoptotic effect of 2‐methoxyestradiol in DS‐sarcoma cells because supplementation with various antioxidants provided only limit protection. Colony formation was not affected by antioxidants. Therefore, in DS‐sarcoma cells, the breakdown of mitochondrial integrity with the subsequent release of mitochondrial nucleases is the main factor in 2‐methoxyestradiol mediated cell death. © 2003 Wiley‐Liss, Inc.