Abietane and icetexane diterpenoids from Salvia candicans

Cárdenas, Jorge; Rodríguez‐Hahn, Lydia

doi:10.1016/0031-9422(94)00569-f

Cited by 26 publications

(31 citation statements)

References 4 publications

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“…The case of hydroxyquinones is one of great importance, since many of these compounds occur in large amounts in many vegetal species of well known biological activity. 3,4 Two main varieties can occur in the nature, both involving different types of hydrogen bond interactions ( Figure 1): the -hydroxy systems, in which the hydrogen bond forms a five-membered ring via the interaction between the oxygen atom of one of the carbonyl-quinonoid groups and another hydroxyl function supported by the -carbon atom to the mentioned carbonyl function. 4 -hydroxyquinones can present hydrogen bonding via the -carbon to the carbonyl function leading to a six-membered ring structure ( Figure 1); the hydroxyl group involved in these structures is usually part of a phenolic function.…”

Section: Introductionmentioning

confidence: 99%

The role of intramolecular hydrogen bonding in the electrochemical behavior of hydroxy-quinones and in semiquinone stability

Frontana¹,

González²

2005

J. Braz. Chem. Soc.

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O estudo de um grupo selecionado de e -hidroxiquinonas ([ ] 2-hidroxi-1,4-naftoquinona 2HNQ, [ ] 5-hidroxi-1,4-naftoquinona 5HNQ and [ , ]5,8-dihidroxi-1,4-naftoquinona DHNQ) mostrou que ambos os tipos de funcionalidades diferem consideravelmente em termos de reatividade eletroquímica e química, e que essas diferenças também se manifestam na comparação de compostos do mesmo grupo. Os resultados provaram que a energia necessária para reduzir eletroquimicamente as hidroxoquinonas estudadas está relacionada com a estabilidade intramolecular das ligações de hidrogênio (IHBs) e com as reações de acoplamento que ocorrem durante a redução eletroquímica, tal como a seqüência de auto-protonação em 2HNQ. A análise da cinética de transferência de elétron associada com a redução monoeletronica que ocorre para 5HNQ e DHNQ mostraram que os efeitos IHB não afetam a cinética do primeiro processo de redução, mas induzem a grandes mudanças na cinética de segunda transferência eletrônica. Isso sugere que as semiquinonas são quimicamente diferentes dos compostos estudados, o que foi comprovado pela análise da estrutura eletrônica das semiquinonas por espectroscopia ESR. Essa análise parece relacionada com a perda de simetria no radical gerado eletronicamente e induz a valores ks de menor velocidade para a segunda redução de transferência de 5HNQ, comparada com DHNQ.The study of a selected group of and -hydroxyquinones ([ ] 2-hydroxy-1,4-naphthoquinone 2HNQ, [ ] 5-hydroxy-1,4-naphthoquinone 5HNQ and [ , ]5,8-dihydroxy-1,4-naphthoquinone DHNQ) showed that both type of functionalities differ considerably in terms of electrochemical and chemical reactivity, and these differences are also manifest even upon comparison between compounds of the same group. The results proved that the energy needed to electrochemically reduce the studied hydroxyquinones is related both to the stability of intramolecular hydrogen bonds (IHBs) and coupled chemical reactions occurring during their electrochemical reduction such as self-protonation sequences in 2HNQ. The analysis of the electron transfer kinetics associated with the monoelectronic reductions occurring for 5HNQ and DHNQ showed that IHB effects do not affect the kinetics of the first reduction process, but induce great changes in the second electron transfer kinetics. This suggests that semiquinone species are chemically different for the studied compounds, as was corroborated by the analysis of the electronic structure of semiquinone species by ESR spectroscopy. This analysis seems to be related to the loss of symmetry in the electrogenerated radical and induces a lower rate ks value for the second reduction transfer of 5HNQ, compared with DHNQ.

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Section: Introductionmentioning

confidence: 99%

The role of intramolecular hydrogen bonding in the electrochemical behavior of hydroxy-quinones and in semiquinone stability

Frontana¹,

González²

2005

J. Braz. Chem. Soc.

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“…Our measurements indicate that it shows mp 217‐219 °C. Compound 3 is a less studied molecule, for which, in addition to the original 1976 papers, only isolation reports are available in the literature . An X‐ray diffracted crystal also provided cell parameters in agreement with those reported, the solid state structure was refined to R = 3.4%, and the Flack x = 0.00(18) and Hooft y = 0.05(9) parameters for the correct enantiomer, whose PLUTO plot is shown in Figure , provided the absolute configuration.…”

Section: Resultsmentioning

confidence: 65%

“…The structure of 3 also followed from X‐ray data, while for 5 , no further isolation report is available since then. Icetexone ( 1 ) appeared also in Salvia anastomosans , Salvia candicans , and Salvia pubescens …”

Section: Introductionmentioning

confidence: 99%

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Absolute configuration of the diterpenoids icetexone and conacytone from Salvia ballotaeflora

et al. 2017

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Detailed literature inspections regarding the diterpenoids icetexone (1) and conacytone (3) reveal that the absolute configuration (AC) of these natural occurring compounds is not rigorously proven, despite they were originally isolated in 1976. This task is now completed by single-crystal X-ray diffraction Flack and Hooft parameters determination after processing data collected with Cu Kα graphite monochromated radiation. The AC of both compounds is further determined by vibrational circular dichroism measurements performed on icetexone acetate (2) and conacytone triacetate (4) since the solubility of 1 and 3 is limited. Comparison of the substituent chemical shifts (SCS) induced by acetylation of 1 and 3 to afford 2 and 4, respectively, reveals that in the case of icetexone, all six SCS values of the quinone ring are in excellent agreement with the expected values, while in the case of conacytone, three agree and three do not agree due to the presence of additional acetates near the quinone ring. Density functional theory calculations performed on 3-hydroxythymoquinone (6) and its tautomer 4-hydroxy-1,2-quinone 7, on 6-hydroxythymoquinone (8) and its tautomer ortho-quinone 9, and on icetexone (1) and the claimed natural occurring ortho-quinone tautomer romulogarzone (5) indicate that 2-hydroxy-1,4-quinones are more stable, by some 11-14 kcal/mol, than their 4-hydroxy-1,2-quinone tautomers, and therefore, romulogarzone (5) is inexistent.

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“…Tanshinones are abietane-type diterpenoids characterized by ortho-or para-benzoquinone chromophores in the aromatic ring C. The occurrence of tanshinones is restricted to species of Labiatae, and they have been repeatedly found in Salvia (Jimenez et al, 1988;Cardenas and Rodriguez-Hanh, 1995) and Coleus species (Mehrotra et al, 1989;Kelecon and Santos, 1985). The broad spectrum of their biological activities, i.e.…”

Section: Introductionmentioning

confidence: 99%

Cytotoxic Abietane Diterpenes from Hyptis martiusii Benth.

Araújo

Lima

Montenegro

et al. 2006

Zeitschrift Für Naturforschung C

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From roots of Hyptis martiusii Benth. two tanshinone diterpenes were isolated, the new 7 -hydroxy-11,14-dioxoabieta-8,12-diene (1) in addition to the known 7α-acetoxy-12-hydroxy-11,14-dioxoabieta-8,12-diene (7α-acetoxyroyleanone) (2). Structures of 1 and 2 were established by spectroscopic means. The cytotoxic activity against five cancer cell lines was evaluated. Compounds 1 and 2 displayed considerable cytotoxic activity against several cancer cell lines with IC 50 values in the range of 3.1 to 11.5 µg/ml and 0.9 to 7.6 µg/ml, respectively. The cytotoxic activity seemed to be related to inhibition of DNA synthesis, as revealed by the reduction of 5-bromo-2Ј-deoxyuridine incorporation and induction of apoptosis, as indicated by the acridine orange/ethidium bromide assay and morphological changes after 24 h of incubation in leukemic cells.

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Abietane and icetexane diterpenoids from Salvia candicans

Cited by 26 publications

References 4 publications

The role of intramolecular hydrogen bonding in the electrochemical behavior of hydroxy-quinones and in semiquinone stability

The role of intramolecular hydrogen bonding in the electrochemical behavior of hydroxy-quinones and in semiquinone stability

Absolute configuration of the diterpenoids icetexone and conacytone from Salvia ballotaeflora

Cytotoxic Abietane Diterpenes from Hyptis martiusii Benth.

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