Browsing by Author "Green, Ivan R."

Now showing 1 - 7 of 7
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    4-Benzyloxylonchocarpin and muracatanes A-C from Ranunculus muricatus L. and their biological effects
    (MDPI, 2020-11-17) Hussain, Hidayat; Ali, Iftikhar; Wang, Daijie; Mamadalieva, Nilufar Z.; Hussain, Wahid; Csuk, Rene; Loesche, Anne; Fischer, Lucie; Staerk, Dan; Anam, Syariful; AlZain, Mashail N.; Mushtaq, Maria; Ul-Haq, Zaheer; Ullah, Riaz; Noman, Omar M.; Abbas, Ghulam; Green, Ivan R.
    ENGLISH ABSTRACT: Ranunculus muricatus L. is a spiny fruit buttercup that is used in various traditional medicinal systems. In the current investigation of R. muricatus, the new chalcone 4-benzyloxylonchocarpin (1), the new anthraquinone muracatanes A (2), the new-to-nature anthraquinone muracatanes B (3), and the new naphthalene analog muracatanes C (4) were isolated, in addition to the three previously reported compounds, 4-methoxylonchocarpin (5), β-sitosterol (6), and β-sitosterol β-D-glucopyranoside (7). Their structures were elucidated using 1D (1H and 13C) and 2D (COSY, HSQC, and HMBC) NMR spectroscopy and HR-ESI-MS. Chalcone 1 showed potent acetylcholinesterase inhibitory effects with Ki of 5.39 µM and Ki′ of 3.54 µM, but none of the isolated compounds showed inhibitory activity towards butyrylcholinesterase. Anthraquinone 3 illustrated α-glucosidase inhibitory effects with IC50-values of 164.46 ± 83.04 µM. Compound 5 displayed moderate cytotoxic activity towards ovarian carcinoma (A2780, IC50 = 25.4 µM), colorectal adenocarcinoma (HT29, IC50 = 20.2 µM), breast cancer (MCF7, IC50 = 23.7 µM), and thyroid carcinoma (SW1736, IC50 = 26.2 µM) while it was inactive towards pharynx carcinoma (FaDu: IC50 > 30 µM).
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    Alkaloids with activity against the Zika virus vector Aedes aegypti (L.) - crinsarnine and sarniensinol, two new crinine and mesembrine type alkaloids isolated from the South African Plant Nerine sarniensis
    (MDPI, 2016-10-27) Masi, Marco; Cala, Antonio; Tabanca, Nurhayat; Cimmino, Alessio; Green, Ivan R.; Bloomquist, Jeffrey R.; Van Otterlo, Willem A. L.; Macias, Francisco A.; Evidente, Antonio
    Two new Amaryllidaceae alkaloids, belonging to the mesembrine- and crinine-types, named crinsarnine (1) and sarniensinol (2), were isolated from the dried bulbs of Nerine sarniensis together with bowdensine (3), sarniensine (4), hippadine (5) and 1-O-acetyl-lycorine (6). Crinsarnine (1) and sarniensinol (2) were characterized using spectroscopic and chiroptical methods as (1S,2S,4aR,10bS)-2,7-dimethoxy-1,2,3,4,4a,6-hexahydro-5,11b-ethano[1,3]dioxolo-[4,5-j]phenanthridin- 1-yl acetate and (6-(3aR,4Z,6S,7aS)-6-methoxy-1-methyl-2,3,3a,6,7,7a-hexa-hydro-1H-indol-3a-yl)benzo [d][1,3]dioxol-5-yl)methanol, respectively. Furthermore, the complete spectroscopic characterization of bowdensine (3) is reported for the first time. Compounds 1–6 were evaluated against the Orlando reference strain of Aedes aegypti. None of compounds showed mortality against 1st instar Ae. aegypti larvae at the concentrations tested. In adult topical bioassays, only 1 displayed adulticidal activity with an LD50 = 2.29 ± 0.049 µg/mosquito. As regards the structure-activity relationship, the pretazettine and crinine scaffold in 2 and 4 and in 1 and 3 respectively, proved to be important for their activity, while the pyrrole[de]phenanthridine scaffold present in 5 and 6 was important for their reactivity. Among the pretazettine group compounds, opening of the B ring or the presence of a B ring lactone as well as the trans-stereochemistry of the A/B ring junction, appears to be important for activity, while in crinine-type alkaloids, the substituent at C-2 seems to play a role in their activity
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    Characterization and cardiovascular effects of (13S)-9α,13α-epoxylabda-6β(19),15(14)diol dilactone, a diterpenoid isolated from Leonotis leonurus
    (University of KwaZulu-Natal, 2008) Obikeze, Kene C.; McKenzie, Jean M.; Green, Ivan R.; Mugaboa, Pierre
    A new diterpenoid, (13S)-9α,13α-epoxylabda-6β(19),15(14)diol dilactone (1), was isolated from Leonotis leonurus and the structure determined via NMR analysis. The compound causes significant changes in blood pressure of anaesthetized normotensive rats and exhibits a negative chronotropic effect.
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    First-principles study on chromium-substituted α-cobalt oxyhydroxides for efficient oxygen evolution reaction
    (American Chemical Society, 2020-06) Shamraiz, Umair; Badshah, Amin; Raza, Bareera; Green, Ivan R.
    Owing to their catalytic, electronic, and optical properties, metal hydroxides are extensively used in energy applications. Despite recent progress, the synthesis of monolayer metal hydroxides with unique structures remains a challenge, and their potential use in the oxygen evolution reaction (OER) has not been fully investigated. Herein, the fabrication of chromium-substituted α-cobalt hydroxide through a simple co-precipitation method under optimum conditions at higher pH is described. Such nanostructures can competently catalyze oxygen evolution reactions to produce a current density of 10 mA cm–2 at an overpotential of 240 mV in alkaline medium. Microscopic, electrochemical, and spectroscopic analyses reveal that the exceptional OER performance originates from thin monolayer sheets with exposed active sites and partially due to the substitution of α-CoOOH with Cr. The phase purity is highlighted through powder X-ray diffraction (PXRD), energy-dispersive X-ray (EDX) mapping, and X-ray photoelectron spectroscopy (XPS) analysis.
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    A review on recent syntheses of Amaryllidaceae alkaloids and isocarbostyrils (time period mid-2016 to 2017)
    (Sage Publishing, 2018) Van Otterlo, Willem A. L.; Green, Ivan R.
    Alkaloids from the Amaryllidaceae have become valuable targets for synthetic organic chemists, mainly due to their wide variety of bioactivities and potential for utilization in medicinal chemistry ventures. In addition, the structural complexity of a number of these alkaloids has also been a reason for the interest in these compounds. In this review, the last 18 months of literature was perused and synthetic highlights have been presented here, with the hope to further focus attention on this interesting class of compounds and to encourage others to synthesize these compounds and their derivatives and/or analogues. The review contains examples of syntheses from most of the important alkaloid scaffold classes previously isolated from the Amaryllidaceae, namely: lycorine, crinine, galanthamine, tazettine, montanine, phenanthridone, phenanthridine, plicamine, mesembrine and some minor scaffolds (like gracilamine).
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    Synthesis of 2-substituted tetrahydroisoquinolin-6-ols: potential scaffolds for estrogen receptor modulation and / or microtubule degradation
    (ARKAT USA, 2019) Mabank, Tanya; Alexandre, Kabamba B.; Pelly, Stephen C.; Green, Ivan R.; Van Otterlo, Willem A. L.
    ENGLISH ABSTRACT: 6-Methoxytetrahydroisoquinoline hydrochloride was converted into four small libraries of substituted ureas, thioureas, sulfonamides and N-aryls, using the tetrahydroisoquinoline nitrogen as the scaffold-linking atom. Some of the compounds were evaluated for their ability to inhibit cell proliferation using the MCF7 (invasive ductal carcinoma) cell line.
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    Synthesis of pyrrolocarbazoles with N-substituted alkynyl-, alkylcyano- and alkylhydroxyl-groups
    (ARKAT USA, 2020) Van der Westhuyzen, Alet E.; Hadjegeorgiou, Kathy; Green, Ivan R.; Pelly, Stephen C.; Van Otterlo, Willem A. L.
    ENGLISH ABSTRACT: Due to their involvement in almost all stages of cellular life, kinase biomolecular catalysts have been linked to cancer development and, thus, remain attractive drug targets for cancer therapeutics. 6-(3ꞌ-Hydroxypropyl)-, 6-(2ꞌ-hydroxyethyl)-, 6-(2ꞌ-propynyl)- and 6-(3ꞌ-propanenitrile)-pyrrolo[3,4-c]carbazole-1,3(2H,6H)-diones were synthesized as potential small molecule EGFR kinase inhibitors. The pyrrolocarbazole compounds were synthesized by way of a Diels-Alder approach involving N-alkylated 2-vinyl-1H-indole and maleimide as starting materials followed by aromatization with MnO2.