[Show abstract][Hide abstract] ABSTRACT: Five flavonoids (rutin, asebotin, 3-hydroxyasebotin, quercetin-3-O-beta-D-xylopyranoside, and a racemic mixture of catechin) and caffeic acid were isolated and identified for the first time from seagrass, Thalassodendron ciliatum, collected from the Hurghada region in Egypt. The crude extract and the isolated pure compounds were evaluated for their cytotoxic activities against HCT-116, HEPG, MCF-7, and HeLa human cancer cell lines, for their antiviral activity against Herpes Simplex and hepatitis A viruses, and for their antioxidant activity.
[Show abstract][Hide abstract] ABSTRACT: Euclea natalensis A.DC., Knowltonia vesicatoria (L.f) Sims, and Pelargonium sidoides DC. are South African plants traditionally used to treat tuberculosis. Extracts from these plants were used in combination with isoniazid (INH) to investigate the possibility of synergy with respect to antimycobacterial activity. The ethanol extract of K. vesicatoria was subjected to fractionation to identify the active compounds. The activity of the Knowltonia extract remained superior to the fractions with a minimum inhibitory concentration (MIC) of 625.0 μg/mL against Mycobacterium smegmatis and an MIC of 50.00 μg/mL against M. tuberculosis. The K. vesicatoria extract was tested against two different drug-resistant strains of M. tuberculosis, which resulted in an MIC of 50.00 μg/mL on both strains. The combination of K. vesicatoria with INH exhibited the best synergistic antimycobacterial activity with a fractional inhibitory concentration index of 0.25 (a combined concentration of 6.28 μg/mL). A fifty percent inhibitory concentration of this combination against U937 cells was 121.0 μg/mL. Two compounds, stigmasta-5,23-dien-3-ol (1) and 5-(hydroxymethyl)furan-2(5H)-one (2), were isolated from K. vesicatoria as the first report of isolation for both compounds from this plant and the first report of antimycobacterial activity. Compound (1) was active against drug-sensitive M. tuberculosis with an MIC of 50.00 μg/mL.
Evidence-based Complementary and Alternative Medicine 05/2012; 2012(2):808979. DOI:10.1155/2012/808979 · 1.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Sideritol, C20H32O3, diterpenoid isolated from Sideritisangustifolia Lag., has been shown to be ent-13-atisen-1β, 16α, 17-triol (1). Sideritol is the first reported oxygenated diterpenoid of the ent-atisane class which does not contain nitrogen. The transformation of sideritol into ent-17-noratisane (11), previously prepared from atisine, rigorously defines the skeleton and absolute stereochemistry of sideritol.
Canadian Journal of Chemistry 02/2011; 52(15):2792-2797. DOI:10.1139/v74-407 · 1.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The diterpenoids jativatriol (1) and sideritol (2) have been correlated by transformation of each into ent-17-noratis-13-en-1,16-dione (9). In the case of jativatriol, a simple procedure is described for transforming the ent-5-beyerene derivative into an ent-13-atisene derivative.
Canadian Journal of Chemistry 02/2011; 53(8):1172-1175. DOI:10.1139/v75-162 · 1.06 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Two new diterpenoids, ent-7α-acetoxy-15-beyeren-18-oic acid and (13S,15S)-6β,7α,12α,19-tetrahydroxy-13β,16-cyclo-8-abietene-11,14-dione, have been isolated from Plectranthus saccatus and Plectranthus porcatus, respectively, and their structures were established by 1D and 2D NMR spectroscopic studies. The new diterpenes showed no activity against Gram-negative bacteria and Candida albicans (yeast strain). Among Gram-positive bacteria, the lower MIC value was 62.50μg/ml for the abietane derivative against Staphylococcus aureus ATCC 6538.
[Show abstract][Hide abstract] ABSTRACT: Parvifloron D was isolated from Plectranthus ecklonii together with sugiol and mixtures of β-sitosterol and stigmasterol and ursolic and oleanolic acids. Treatment of parvifloron D [2α-(4-hydroxy)benzoyloxy-11-hydroxy-5,7,9(11),13-abietatetraen-12-one] with acid-washed molecular sieves gave the microstegiol derivative 2β-(4-hydroxy)benzoyloxy-11β-hydroxy-4(5→11),20(10→5)diabeo-5(10),6,8,13-abietatetraen-12-one in a moderate yield (26%). The new microstegiol derivative inhibited the growth of some Staphylococcus and Enterococcus species with significant MIC values ranging from 3.91 to 7.81μg/ml.
[Show abstract][Hide abstract] ABSTRACT: Some 4α, 18-epoxy-neo-clerodane diterpenoids possessing oxygenated functions at the C-6 and C-19 carbons have been subjected to oxirane-opening reactions with several reagents obtaining chlorohydrins, 4-hydroxy-6,18-ethers, 4-hydroxy-18-O-methyl- and 18-O-acetyl derivatives, allylic C-18 primary alcohols and 4,6,18 and 4,6,19- orthoacetates. These results revealed that the functionality at C-6 and its stereochemistry determine the course of the reaction and affect the retention or inversion of the configuration at the C-4 asymmetric centre. In the light of these reactions, a hypothesis on the biogenetic pathway of some neo-clerodane diterpenoids isolated from Teucrium species is proposed. Moreover, useful criteria for establishing the stereochemistry at C-4 in these derivatives, as well as the unambiguous assignment of the structure of montanin E by an X-ray diffraction analysis and the results achieved in the biological assay as insect antifeedants of several non-natural neo-clerodane derivatives are also reported.
[Show abstract][Hide abstract] ABSTRACT: A study of the 1H and 13C NMR, spectra, variation of the molecular rotations and behavior in the CD exciton chirality method of several C-12 epimers of 12-hydroxy-, 12-acetory- and 12-benzoyloxy-neo-clerodane derivatives has been achieved, providing useful alternative methods for establishing the C-12 absolute configuration of this kind of compounds.
[Show abstract][Hide abstract] ABSTRACT: A new diterpenoid, 19-acetoxypregaleopsin, has been isolated from the aerial parts of Leonurus cardiaca. Its structure, [(13R)-8β,19-diacetoxy-9α,13; 15,16-diepoxylabd-14-en-7-one] was established by spectroscopic means.
[Show abstract][Hide abstract] ABSTRACT: An n-hexane extract and the sesquiterpene polygodial isolated from the bark of Drimys winteri J.R. Forster & G. Forster (Winteraceae) were tested to assess their ability to inhibit settling of the aphid Nasonovia ribisnigri Mosley on lettuce leaves; assessments were made using a choice and no-choice leaf-disk assay. The n-hexane extract and the
polygodial both significantly inhibited settling in the choice and no-choice tests, but their application on lettuce leaves
did not result in any aphid mortality. Probing behavior of N. ribisnigri on polygodial-treated plants was assessed by means of the electrical penetration graph technique. Polygodial interfered with
aphid probing behavior by reducing the total probing time, the number of probes, and the number of intracellular punctures.
Aphids did not reach the sieve elements of polygodial-treated plants during the 2-h access period. Both tested compounds have
the potential to be used in the development of lettuce aphid control agents to reduce the risk of virus transmission.
KeywordsAntifeedants-Canelo-Electrical penetration graph (EPG)-Plant extracts-Winter’s bark tree
[Show abstract][Hide abstract] ABSTRACT: The antimycobacterial activities of eight diterpenes, 1-8, isolated previously from Plectranthus and eleven esters, 9-19, of 7alpha-acetoxy-6beta,12-dihydroxyabieta-8,12-diene-11,14-dione (5) were evaluated against the MTB strains H(37)Rv and MDR. Only diterpenoids with a quinone framework revealed anti-MTB activity. Abietane 5 and its 6,12-dibenzoyl, 12-methoxybenzoyl, 12-chlorobenzoyl, and 12-nitrobenzoyl esters, 9, 11, 12, and 13, respectively, showed potent activities against the MDR strain with MIC values between 3.12 and 0.39 microg/ml. Cytotoxic activities towards 3T3 and Vero cells were also evaluated. Compound 11, with the best selectivity index, may be a suitable lead for further chemical modifications. The complete structural elucidation of the new esters, 9-14, 16, 18, and 19, as well as the NMR data of known derivatives 15 and 17 are reported.
[Show abstract][Hide abstract] ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
[Show abstract][Hide abstract] ABSTRACT: Furanosyl and pyranosyl chlorides react with aryllithium derivatives, obtained by directed ortho-lithiation of activated arenes, to give C-1 aryl glycals in moderate yields.
[Show abstract][Hide abstract] ABSTRACT: Four acyloxy-isopimarane derivatives along with two known isopimarane diterpenoids, the flavone cirsimaritin and the sterols beta-sitosterol and stigmasterol were isolated from the aerial parts of Aeollanthus rydingianus. The structures of the compounds were established on the basis of spectroscopic analysis and chemical evidence. The isolated substances were screened for antimicrobial activity against Gram-positive and Gram-negative bacteria and a yeast strain. 19-Acetoxy-7,15-isopimaradien-3beta-ol and 7,15-isopimaradien-19-ol showed minimum inhibitory concentration (MIC) values of 3.90-15.62 microg/ml for Staphylococcus aureus and of 7.81microg/ml for Enterococcus hirae.
[Show abstract][Hide abstract] ABSTRACT: A new rearranged abietane diterpenoid, teuvincenone J, was isolated from the root of Teucrium lanigerum Lag. (Labiatae) together with four known compounds, teuvincenones A–D. The structure of the new diterpene [12,16-epoxy-11,14-dihydroxy-17(15 → 16)-abeo-3α,18-cyclo-8,11,13,15-abietatetraen-7-one] was established by 1D- and 2D-NMR spectroscopic means. These diterpenes could be significant from a chemotaxonomic point of view.
[Show abstract][Hide abstract] ABSTRACT: Salvinorin A (1), a neoclerodane diterpene from the hallucinogenic mint Salvia divinorum, is the only known naturally occurring non-nitrogenous and specific κ-opioid agonist. Some oxidative modifications of the A ring in the congeners of 1 isolated from Salvia splendens salviarin, splenolide B, splendidin and in the non-natural 8-epi-salviarin gave new derivatives, some of which were tested as agonists at opioid receptors. However, none of these compounds were active. The presence of the C-18, C-19 lactone could be at the origin of the observed lack of binding affinity.
[Show abstract][Hide abstract] ABSTRACT: Salvinorin A (1), a neoclerodane diterpene from the hallucinogenic mint Salvia divinorum, is the only known non-nitrogenous and specific kappa-opioid agonist. Several structural congeners of 1 isolated from Salvia splendens (2 - 8) together with a series of semisynthetic derivatives (9 - 24), some of which possess a pyrazoline structural moiety (9, 19 - 22), have been tested for affinity at human mu, delta, and kappa opioid receptors. None of these compounds showed high affinity binding to these receptors. However, 10 showed modest affinity for kappa receptors suggesting other naturally neoclerodanes from different Salvia species may possess opioid affinity.
[Show abstract][Hide abstract] ABSTRACT: A new indanone derivative (1) and two new diterpenoids (2 and 3), together with three known flavonoids, have been isolated from an ethanol extract of the leaves of Croton steenkampianus. The structure of 2 was solved by single-crystal X-ray diffraction analysis, whereas those of 1 and 3 were established mainly by 1D and 2D NMR spectroscopic methods. The isolated compounds were tested for their antiplasmodial activity and cytotoxicity. Antiplasmodial assays against chloroquine-susceptible strains (D10 and D6) and the chloroquine-resistant strains (Dd2 and W2) of Plasmodium falciparum showed that compound 2 gave moderate activities at 9.1-15.8 μM, while none of the compounds were cytotoxic against Vero cells.