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Author

Marii Takahashi

Bio: Marii Takahashi is an academic researcher. The author has contributed to research in topic(s): Millettia & Diarylheptanoid. The author has an hindex of 5, co-authored 7 publication(s) receiving 220 citation(s).
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Journal ArticleDOI
TL;DR: From a literature search for reports on the chemical constituents of these plants, most constituents were found to be quinone derivatives or other compounds with unsaturated carbonyl groups.
Abstract: Seventy-five Myanmar timber extracts belonging to 27 families were examined for their leishmanicidal activities. Some timber extracts had significant leishmanicidal activity, especially extracts of Millettia pendula, which exhibited the most potent activity (MLC 3.1 μg/ml, MIC 1.6 μg/ml). Other timber extracts showing potent activity included those from Cedrela serrata, Cedrela toona, Cordia fragrantissima, Calophyllum kunstleri, Dalbergia cultrate, Grevillea robusta, Haplophragma adenophyllum, Michelia champaca, and Tectona grandis. From a literature search for reports on the chemical constituents of these plants, most constituents were found to be quinone derivatives or other compounds with unsaturated carbonyl groups.

68 citations


Journal ArticleDOI
TL;DR: Leishmanicidal activity of 46 natural products including several fern and Betula constituents was examined, and it was found that the carbonyl group at C‐11 is necessary for the activity of biphenyl‐types.
Abstract: Leishmanicidal activity of 46 natural products including several fern and Betula constituents was examined. Several pterosin and atisene compounds from ferns had high activity. Among the triterpenoids the carboxyl group was found to be important for activity. In the diarylheptanoids, the linear-type and the diphenylether-type showed significant activity, and it was found that the carbonyl group at C-11 is necessary for the activity of biphenyl-types. Copyright © 2004 John Wiley & Sons, Ltd.

61 citations


Journal ArticleDOI
TL;DR: The alpha-methylene-gamma-butyrolactone moiety was found to be essential to the potent leishmanicidal effect observed and exhibited potent in vitro leish manicidal activities against Leishmania major.
Abstract: The leishmanicidal compounds isolated from whole plants of Elephantopus mollis H.B.K. were identified as follows. Three new sesquiterpenoid lactones, 2,5-epoxy-2beta-hydroxy-8alpha-(2-methylpropenoyloxy)-4(15),10(14),11(13)-germacratrien-12,6alpha-olide, (4betaH)-8alpha-(2-methylpropenoyloxy)-2-oxo-1(5),10(14), 11(13)-guaiatrien-12,6alpha-olide and (4betaH)-5alpha-hydroxy-8alpha-(2-methylpropenoyloxy)-1(10),11(13)-guaiadiene-12,6alpha-olide, were isolated from Peruvian and Brazilian collections together with four known sesquiterpenoids, molephantin, elephantopin, isoelephantopin and 2-deethoxy-2beta-methoxyphantomolin. They exhibited potent in vitro leishmanicidal activities against Leishmania major. The alpha-methylene-gamma-butyrolactone moiety was found to be essential to the potent leishmanicidal effect observed.

48 citations


Journal ArticleDOI
TL;DR: Two new compounds, 1 and 2, were isolated from the methanol extract of M. pendula and one was found to be a purple pigment in this heartwood and showed the most potent leishmanicidal activity.
Abstract: The in vitro leishmanicidal constituents of Millettia pendula were examined. Two new compounds, 1 (millettilone A) and 2 (millettilone B), were isolated from the methanol extract of M. pendula, together with six known compounds: 3R-claussequinone (3), pendulone (4), secundiflorol I (5), 3,8-dihydroxy-9-methoxypterocarpan (6), 3,10-dihydroxy-7,9-dimethoxypterocarpan (7), and formononetin (8). Among these, pendulone showed the most potent leishmanicidal activity. Compound 2 was found to be a purple pigment in this heartwood. Their chemical structures were elucidated using spectral methods.

26 citations


Journal ArticleDOI
TL;DR: Rhodacyanine dyes, potent antimalarial agents, was found to possess strong antileishmanial activity against Leishmania major in vitro.
Abstract: Rhodacyanine dyes, potent antimalarial agents, was found to possess strong antileishmanial activity against Leishmania major in vitro. The efficacies of several compounds are comparable to one of clinically used amphotericin B.

15 citations


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Journal ArticleDOI
TL;DR: A review of the literature on plant extracts and chemically defined molecules of natural origin showing antileishmanial activity and some aspects of recent antileishesmanial-activity-directed research on natural products are discussed.
Abstract: Infections caused by protozoa of the genus Leishmania are a major worldwide health problem, with high endemicity in developing countries. The incidence of the disease has increased since the emergence of AIDS. In the absence of a vaccine, there is an urgent need for effective drugs to replace/supplement those in current use. The plant kingdom is undoubtedly valuable as a source of new medicinal agents. The present work constitutes a review of the literature on plant extracts and chemically defined molecules of natural origin showing antileishmanial activity. The review refers to 101 plants, their families, and geographical distribution, the parts utilized, the type of extract and the organism tested. It also includes 288 compounds isolated from higher plants and microorganisms, classified into appropriate chemical groups. Some aspects of recent antileishmanial-activity-directed research on natural products are discussed.

395 citations


Journal ArticleDOI
Nigel C. Veitch1Institutions (1)
TL;DR: This account describes 275 new isoflavonoids published between 2008 and 2011 as constituents of the Leguminosae, commenting on their source, identification, biological activity, synthesis, and ecological or chemosystematic significance.
Abstract: Covering: January 2005 to December 2007. Previous review: Nat. Prod. Rep., 2007, 24, 417–464

231 citations


Journal ArticleDOI
Advait Nagle1, Shilpi Khare1, Arun Kumar2, Frantisek Supek1  +7 moreInstitutions (2)
TL;DR: The disease history and parasite biology is described followed by a summary of the currently available treatments and, finally, review reports of novel small molecules with antileishmanial activity.
Abstract: Leishmaniasis is a parasitic disease that presents four main clinical syndromes: cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL), visceral leishmaniasis/kala azar (VL), and post kala azar dermal leishmaniasis (PKDL). Causative Leishmania are protozoan parasites that are transmitted among mammalian hosts by phlebotomine sandflies. In mammalian hosts, parasite cells proliferate inside the host phagocytic cells as round amastigotes. Infection of sandflies with Leishmania occurs during insect feeding on infected mammalian hosts. After introduction into the insect gut together with the blood meal, Leishmania amastigotes transform into elongated flagellated promastigotes that propagate in the insect gut. A new round of infection is initiated after the infected sandfly takes a blood meal from a naive mammalian host and introduces Leishmania parasites into the bite wound in the host dermis (Scheme 1). More than 20 different Leishmania species have been found to cause human leishmaniasis (Table 1). Leishmaniasis is endemic in 98 countries and is closely associated with poverty. More than a million new cases are reported per year and 350 million people are at risk of contracting the infection. For the most severe form of leishmaniasis, VL, ∼300 000 new cases are estimated to occur annually resulting in ∼40 000 deaths. Approximately 90% of all VL cases occur in 3 endemic foci: 1. India, Bangladesh, and Nepal; 2. East Africa; and 3. Brazil. In spite of the high prevalence, currently available treatments for leishmaniasis are inadequate. Pentavalent antimonials, the standard treatment for leishmaniasis for many decades, are not efficacious in Bihar (∼60% of VL cases worldwide) any longer due to widespread resistance to the drug in this region. Several new VL treatments have emerged during the past 10–15 years, but each has serious shortcomings (summarized in Table 2). These include paromomycin (injectable, long treatment, region-dependent efficacy), miltefosine (cost, teratogenicity, long treatment), and liposomal amphotericin B (cost, hospitalization, region-dependent efficacy). An additional challenge is represented by patients with HIV/VL coinfections who are more difficult to cure (lower initial and final cure rates), have greater susceptibility to drug toxicity, and have higher rates of death and relapse. Due to the limitations of the existing treatments, better drugs are urgently needed. Ideally, new VL drugs would be efficacious across all endemic regions, would affect cure in ≤10 days, and would cost <$10 per course (for a complete target product profile for new VL drugs, which was formulated by DNDi, see Table 4).1 Here we describe the disease history and parasite biology followed by a summary of the currently available treatments and, finally, review reports of novel small molecules with antileishmanial activity.

225 citations


Journal ArticleDOI
TL;DR: The current review attempts to give an overview on the potential of such plant-derived natural products as antiprotozoal leads and/or drugs in the fight against NTDs.
Abstract: Infections with protozoan parasites are a major cause of disease and mortality in many tropical countries of the world. Diseases caused by species of the genera Trypanosoma (Human African Trypanosomiasis and Chagas Disease) and Leishmania (various forms of Leishmaniasis) are among the seventeen "Neglected Tropical Diseases" (NTDs) defined by the WHO. Furthermore, malaria (caused by various Plasmodium species) can be considered a neglected disease in certain countries and with regard to availability and affordability of the antimalarials. Living organisms, especially plants, provide an innumerable number of molecules with potential for the treatment of many serious diseases. The current review attempts to give an overview on the potential of such plant-derived natural products as antiprotozoal leads and/or drugs in the fight against NTDs. In part I, a general description of the diseases, the current state of therapy and need for new therapeuticals, assay methods and strategies applied in the search for new plant derived natural products against these diseases and an overview on natural products of terpenoid origin with antiprotozoal potential were given. The present part II compiles the current knowledge on natural products with antiprotozoal activity that are derived from the shikimate pathway (lignans, coumarins, caffeic acid derivatives), quinones of various structural classes, compounds formed via the polyketide pathways (flavonoids and related compounds, chromenes and related benzopyrans and benzofurans, xanthones, acetogenins from Annonaceae and polyacetylenes) as well as the diverse classes of alkaloids. In total, both parts compile the literature on almost 900 different plant-derived natural products and their activity data, taken from over 800 references. These data, as the result of enormous efforts of numerous research groups world-wide, illustrate that plant secondary metabolites represent an immensely rich source of chemical diversity with an extremely high potential to yield a wealth of lead structures towards new therapies for NTDs. Only a small percentage, however, of the roughly 200,000 plant species on earth have been studied chemically and only a small percentage of these plants or their constituents has been investigated for antiprotozoal activity. The repository of plant-derived natural products hence deserves to be investigated even more intensely than it has been up to present.

217 citations


Journal ArticleDOI
TL;DR: The ability of natural receptors to possess differential binding between atropisomers is an important factor when considering active and inactive atrop isomeric drugs, and has required the development of new techniques for atropselective synthesis of desired targets.
Abstract: Covering: up to mid-2015 Recently identified natural atropisomeric compounds with potential medicinal applications are presented. The ability of natural receptors to possess differential binding between atropisomers is an important factor when considering active and inactive atropisomeric drugs, and has required the development of new techniques for atropselective synthesis of desired targets. Advances in this field therefore have significant relevance to modern pharmaceutical and medicinal chemistry. The atropisomeric natural products discussed include hibarimicinone, flavomannins, talaromannins, viriditoxin, rugulotrosin A, abyssomicin C, marinopyrroles, dixiamycins, streptorubin B, ustiloxins A–F, haouamine A, bisnicalaterines, and tedarene B, all of which show significant potential as leads in antibiotic, antiviral and anticancer studies. The importance for the development of common practices regarding atropisomer recognition and classification is also emphasized.

188 citations


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Author's H-index: 5

No. of papers from the Author in previous years
YearPapers
20062
20043
20012