Krishna Prasad Devkota

Tribhuvan University, Kantipura, Central Region, Nepal

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Publications (48)74.1 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Tetra-acetylajugasterone C (TAAC) was found to be one of the naturally occurring compounds of the Cameroonian medicinal plant Vitex cienkowskii which is responsible for a vasorelaxant activity of an extract of this plant. The evaluation of the underlying mechanisms for the relaxing effect of TAAC was determined using aortic rings of rats and mice. TAAC produced a concentration-dependent relaxation in rat artery rings pre-contracted with 1μM noradrenaline (IC50: 8.40μM) or 60mM KCl (IC50: 36.30μM). The nitric oxide synthase inhibitor l-NAME (100μM) and the soluble guanylate cyclase inhibitor ODQ (10μM) significantly attenuated the vasodilatory effect of TAAC. TAAC also exerted a relaxing effect in aorta of wild-type mice (cGKI(+/+); IC50=13.04μM) but a weaker effect in aorta of mice lacking cGMP-dependent protein kinase I (cGKI(-/-); IC50=36.12μM). The involvement of calcium channels was studied in rings pre-incubated in calcium-free buffer and primed with 1μM noradrenaline prior to addition of calcium to elicit contraction. TAAC (100μM) completely inhibited the resulting calcium-induced vasoconstriction. The same concentration of TAAC showed a stronger effect on the tonic than on the phasic component of noradrenaline-induced contraction. This study shows that TAAC, a newly detected constituent of Vitex cienkowskii contributes to the relaxing effect of an extract of the plant. The effect is partially mediated by the involvement of the NO/cGMP pathway of the smooth muscle but additionally inhibition of calcium influx into the cell may play a role.
    Phytomedicine: international journal of phytotherapy and phytopharmacology 03/2014; · 2.97 Impact Factor
  • Medicinal Plant Research in Africa: Pharmacology and Chemistry, first edtion edited by Victor Kuete, 07/2013: chapter 14: pages 557-605; Elsevier., ISBN: 9780124059276
  • Medicinal Plant Research in Africa,, 1st Edition edited by V Kuete, 07/2013: chapter 14. Alkaloids from the Medicinal Plants of Africa; Elsevier., ISBN: 9780124059276
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    ABSTRACT: The methanol extract of dried fruits of Odyendyea gabonensis afforded one new quassinoid [(-)-odyendanol (1)], one new canthin-6-one alkaloid [9-hydroxy-5-methoxycanthin-6-one (4)], and two new steroids [22E, 24R-stigmasta-5,22-diene-3,7-dione (7) and 22E,24R-stigmast-22-ene-3,7-dione (8)] along with fourteen known compounds. The structures of all compounds were established by analyzing the spectroscopic data. The 13C-NMR values of (-)-odyendene (2) and (-)-odyendane (3), as well as the single-crystal X-ray structure of 5-methoxycanthin-6-one (6) are also reported.The oxidative burst inhibitory activity of pure compounds 1-12 was determined by the chemoluminescence assay, and cytotoxic activities of compounds 2-6 against the human prostate cancer cell PC-3 line were evaluated. Compounds 1-6 exhibited a clear suppressive effect on the phagocytosis response upon activation with serum-opsonized zymosan in the range of IC50 = 0.9-2.0 µM versus ibuprofen with IC50 = 12.1 µM, while all canthin-6-one alkaloids (4-6) displayed moderate cytotoxic activity against the human prostate cancer cell PC-3 line, with IC50 values ranging from 13.5-15.4 µM versus doxorubicine with IC50 = 1.5 µM.
    Planta Medica 11/2012; · 2.35 Impact Factor
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    ABSTRACT: One new xanthone, caroxanthone (1) together with six known xanthones, 4-prenyl-2-(3,7-dimethyl-2,6-octadienyl)-1,3,5,8-tetrahydroxyxanthone (2), smeathxanthone A (3), gartanin (4), euxanthone (5), 8-hydroxycudraxanthone G (6) and morusignin I (7) were isolated from the stem bark of Garcinia nobilis. The structures were determined by 1D- and 2D-NMR techniques. All these compounds were tested for anti-glycation, α-glucosidase and α-chymotrypsin activities. Some of them exhibited strong to moderate α-glucosidase activities, while none of them inhibited α-chymotrypsin. Compounds 6 and 7 were found to be modest α-glucosidase inhibitors with IC50 values of 76 μM and 84 μM, respectively.
    Phytochemistry Letters 01/2012; 5:236–239. · 1.18 Impact Factor
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    ABSTRACT: Three new β-indoloquinazoline alkaloids, orirenierine A (1), B (2) and C (4), together with eleven known compounds were isolated from the methanol extract of the stems of Oricia renieri. The structures of all compounds were determined by comprehensive analyses of their spectroscopic data and comparison with literature information. The alkaloids 9-11 were isolated for the first time from this genus. All compounds were tested for their activity against bacteria, fungi, and plant pathogen oomycetes using the paper disk agar diffusion assay. The agar diffusion test gave only low antimicrobial activities, corresponding to MICs > 1 mg/mL. However, compounds 1-4 and 11 exhibited a strong suppressive effect on phagocytosis response upon activation with serum opsonized zymosan in the range of IC(50) = 2.6-6.5 µM, while low cytotoxic activity against the human Caucasian prostate adenocarcinoma cell line PC-3 was observed with IC(50) values ranging from 22.9 to 39.4 µM.
    Planta Medica 09/2011; 78(1):71-5. · 2.35 Impact Factor
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    ABSTRACT: Bioassay-guided fractionation of the methanol extract of the stem bark of Klainedoxa gabonensis Pierre ex Engl. (Irvingiaceae) afforded 12 compounds, namely, ellagic acid (1), ellagic acid 3,3'-dimethylether (2), gallic acid (3), methyl gallate (4), lupeol (5), β-amyrin (7), erythrodiol (8), oleanolic acid (9), betulinic acid (6), hederagenin (10), bayogenin acid (11), and stigmasterol-3-O-β-d-glucopyranoside (12). Compounds 1-3 and 7-12 were isolated for the first time from this genus. The structures were established on the basis of 1D/2D NMR experiments and mass spectrometric data. Crude extract, fractions (A, B, C and D) and pure compounds were tested for their antimicrobial activity using paper disk agar diffusion assay. The test delivered a range of low to high activities for phenolic compounds 1-4, low or missing activities for terpenoid compounds 5-11, and impressive very high antibacterial/antifungal values for two fractions C and D probably due to synergistic effects of compounds. The broth microdilution assay revealed MICs of 15.4-115.1 μg/mL for phenolic compounds, MICs higher than 1 mg/mL for terpenoids and MICs of 4.5-30.3 μg/mL for fractions C and D. The determination of the radical scavenging activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay gave high antioxidant values for the methanol extract and fraction D (IC(50) 10.45 and 5.50 μg/mL) as well as for the phenolic compounds 1-4 (IC(50) 45.50-48.25 mM) compared to the standard 3-t-butyl-4-hydroxyanisole (BHA) (IC(50) 44.20 mM).
    Pharmaceutical Biology 10/2010; 48(10):1124-9. · 1.21 Impact Factor
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    ABSTRACT: Vitex cienkowskii Kotschy & Peyritsch is a deciduous tree, prescribed by Cameroonian traditional healers as one of the most popular plant widely used in many disorders including cardiovascular diseases. The preliminary pharmacological studies carried out on Vitex cienkowskii showed its vasorelaxant activities on guinea-pig aortic rings. The present work evaluated the vasorelaxant activity of extract and isolated compounds from Vitex cienkowskii. Rat aortic rings were used to evaluate the in vitro vascular effect of the extract. The antioxidant activity was determined by measuring the reduction of the free radical 1,1-diphenyl-1-picryl-hydrazyl (DPPH). Vitex cienkowskii induced significant relaxation in a concentration- and endothelium-dependent manner (EC(50)=12.12 μg/ml, CH(2)Cl(2)-MeOH, 1:1) and did not produce a vasorelaxant effect on contraction evoked by KCl (60 mM). In order to determine its mode of action, Vitex cienkowskii-induced relaxant effect was evaluated in the presence of indomethacin (10 μM), L-NAME (100 μM), ODQ (1 μM) and SQ22356 (100 μM). Relaxation was significantly blocked by L-NAME and ODQ. These results indicate that Vitex cienkowskii-mediated relaxation is endothelium dependent, probably due to NO release, and the consequent activation of vascular smooth muscle soluble guanylate cyclase (sGC), a signal transduction enzyme that forms the second messenger cGMP. Bio-guided study of Vitex cienkowskii allowed the isolation of the known pentacyclic triterpenoids and a ceramide. It is the first report of salvin A, maslinic acid and a ceramide from Vitex cienkowskii. The activity induced by these compounds indicated that they may be partly responsible for the vasorelaxant effect of the plant extract. A dose of 40 mg/kg of CH(2)Cl(2)-MeOH (1:1) extract administered intravenously induced a decrease of mean arterial pressure but did not affect the heart rate. Moreover the plant extracts were found to be highly active in the DPPH radical scavenging assay. Vitex cienkowskii extract possesses antioxidant property, vasorelaxing, and hypotensive effect linked to the endothelium related factors, where nitric oxide is involved.
    Journal of ethnopharmacology 10/2010; 133(1):204-12. · 2.32 Impact Factor
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    ABSTRACT: Bioassay-guided fractionation of the fruit pericarp of Pentadesma butyracea, using the antiplasmodial test, led to the isolation of a new xanthone, named pentadexanthone (1), together with six known compounds: cratoxylone (2), α-mangostin (3), 1,3,5-trihydroxy-2-methoxyxanthone (4), garcinone E (5), (-)-epicathechin (6), and lupeol (7). The structure of 1 was elucidated by spectroscopic data analysis. An antiplasmodial assay was performed with the isolates, in which compounds 1- 3 and 5 exhibited potent activity in vitro against Plasmodium falciparum chloroquine-resistant strain W2, with IC₅₀ values below 3 µM.
    Planta Medica 10/2010; 77(4):377-9. · 2.35 Impact Factor
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    ABSTRACT: Four new 5 alpha-pregnane-type steroidal alkaloids, hookerianamides L(1), M(2), N(3), and O(4), and a known N-formylchonemorphine (5) have been isolated by acid-base extraction of the dichloromethane extract of Sarcococca hookeriana. The structures of all compounds were determined with spectroscopic techniques and by comparison with literature data. All compounds displayed antileishmanial and antibacterial properties. Compounds 1, 4, and 5 were found to be more potent than standard pentamidine (IC (50) = 9.59 microg/mL) with respect to leishmanicidal activity. The minimum inhibitory concentration of most of the compounds against Bacillus subtilis, Streptococcus minor, and Streptococcus ferus was lower than that of the standard ampicillin.
    Planta Medica 02/2010; 76(10):1022-5. · 2.35 Impact Factor
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    ABSTRACT: Four new long-chain compounds, leucoperoxyterpene (1), leucoester (2), leucoic acid (3), and leucoenoic acid (4) has been isolated from aerial parts of the medicinal plant Leucosceptrum canum together with fifteen known compounds. Compound 1 was found to be a member of the rare class of peroxy open chain natural products. The structures of all compounds were assigned by means of modern spectroscopic techniques. All compounds were tested for their antibacterial activities against Bacillus subtilis, Escherichia coli, Micrococcus luteus, Pseudomonas agarici, Streptococcus minor, and Streptococcus ferus, in which, compounds 1, and 10–15 exhibited potent to moderate activities.
    Phytochemistry Letters - PHYTOCHEM LETT. 01/2010; 3(1):24-28.
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    ABSTRACT: Phytochemical investigation of the stem bark of Beilschmiedia zenkeri led to the isolation of four new methoxylated flavonoid derivatives, (2S,4R)-5,6,7-trimethoxyflavan-4-ol (1), (2S,4R)-4,5,6,7-tetramethoxyflavan (2), beilschmieflavonoid A (3), and beilschmieflavonoid B (4), together with seven known compounds. The structures of 1-4 were established by spectroscopic methods, and their relative configurations confirmed by X-ray crystallographic and CD analysis. The isolated compounds were evaluated in vitro for their antibacterial activity against three strains of bacteria, Pseudomonas agarici, Bacillus subtilis, and Streptococcus minor, and for their antiplasmodial activity against Plasmodium falciparum, chloroquine-resistant strain W2.
    Journal of Natural Products 11/2009; 72(12):2130-4. · 3.29 Impact Factor
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    ABSTRACT: Fungal infections represent a significant cause of morbidity and mortality especially in immunocompromised patients in the world today. Dichloromethane (DM) and aqueous (W) extracts of nine plants used traditionally for the treatment of fungal infections in Bukoba rural district in Tanzania were screened for antifungal activity against Candida albicans, Cryptococcus neoformans, and Aspergillus niger using agar well and disk diffusion methods. Dichloromethane extracts of Capparis erythrocarpos [CE] Isert (Capparaceae), Cussonia arborea [CA] Hochst. Ex A. Rich (Araliaceae), Dracaena steudneri [DS] Engl. (Dracaenaceae), Lannea schimperi [LS] (A. Rich) Engl. (Anacardiaceae), Rauvolfia vomitoria [RV] Afz (Apocynaceae), and Sapium ellipticum [SE] (Krauss) Pax (Euphorbiaceae) showed activity against all three fungi. Extracts of Rumex usambarensis [RU] (Dammer) Dammer (Polygonaceae) and Zehneria scabra [ZS] (L.f.) Sond. (Cucurbitaceae) had an activity limited to only one or two of the test organisms. Rhoicissus tridentata [RT] (L.f.) Wild & Drum (Vitaceae) was the only plant without activity. Fractions of the active extracts CE, CA, DS, LS, and SE exhibited higher antifungal activity against one or more of the three fungi. Four compounds isolated from S. ellipticum also exhibited antifungal activity against one or more of the three fungi. The minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs), determined using the microplate assay method, ranged between 0.4 and 50.0 μg/mL for crude extracts, 1.6 and 50.0 μg/mL for semi-purified fractions, and 0.12 and 1.0 μg/mL for pure compounds, as compared to 0.016–1.5 μg/mL for fluconazole. We confirm the potential of traditionally used plants as a source of new drugs for treatment of fungal infections.
    07/2009; 47(8):708-716.
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    ABSTRACT: Three endiandric acid derivatives, beilschmiedic acids A, B and C were isolated from the stem bark of Beilschmiedia anacardioides together with the known beta-sitosterol. Their structures were established by means of modern spectroscopic techniques. The relative configuration of compound 1 was determined by single crystal X-ray analysis. The antibacterial activities of compounds A,B,C were evaluated in vitro against five strains of microbes. Compound C showed strong activity against Bacillus subtilis, Micrococcus luteus and Streptococcus faecalis (MICs below 23 microM). This Compound was more active than the reference antibiotic ampicillin against B. subtilis and M. luteus.
    Phytochemistry 05/2009; 70(5):684-8. · 3.35 Impact Factor
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    ABSTRACT: Five new amide alkaloids, N-(4-hydroxyphenethyl)octacosanamide (1), N-(4-hydroxyphenethyl)hexacosanamide (2), N-(4-hydroxyphenethyl)decanamide (3), N-vanilloyltyramine (4), and N-[O-docosanoylvanilloyl]tyramine (5), were isolated from Fagara macrophylla, together with 15 known compounds. Their structures were established by using spectroscopic techniques, chemical reactions, and comparison with previously known analogues. A cytotoxicity assay was performed with the isolates, in which compounds 4, 8, and 9 were found to possess moderate to weak activity, with IC(50) values of 30.5, 11.5, and 13.5 microg/mL, respectively.
    Planta Medica 03/2009; 75(5):517-21. · 2.35 Impact Factor
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 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.
    ChemInform 01/2009; 40(34).
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    ABSTRACT: Two new β-indoloquinazoline alkaloids, orisuaveoline A (1) and orisuaveoline B (2), two new furoquinoline alkaloids, quinosuaveoline A (5) and quinosuaveoline B (6), and 12 known compounds were isolated from Oricia suaveolens. The structures of the new compounds were deduced by spectroscopic studies. The absolute configuration of nkolbisine (4) was also determined. Compounds 2, 3, 6−8, 10, and 14 were evaluated for oxidative burst inhibitory activity in a chemoluminescence assay and for cytotoxicity against A549 lung carcinoma cells.
    Journal of Natural Products 10/2008; 71(11). · 3.29 Impact Factor
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    ABSTRACT: The bioassay-guided phytochemical investigation of Sarcococca hookeriana with respect to cholinesterase inhibitory properties has yielded two new 5alpha-pregnane-type steroidal alkaloids, hookerianamides J (1) and K (2), along with eight known compounds (3-10). The structures of 1 and 2 were elucidated by spectroscopic methods. These compounds displayed good to moderate activities in vitro against the enzymes acetylcholinesterase (IC 50 8.1-48.5 microM) and butyrylcholinesterase (IC 50 0.4-4.0 microM). Compounds 1-10 were also tested in vitro for their leishmanicidal activity against Leishmania major and for their antibacterial activities against Bacillus subtilis, Micrococcus luteus, Streptococcus faecalis, and Pseudomonas pallida.
    Journal of Natural Products 09/2008; 71(8):1481-4. · 3.29 Impact Factor
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    ABSTRACT: The plants of the family Buxaceae are widely used in traditional medicine and constitute rich sources of terpenoidal alkaloids. Compounds of this family have been the subject of numerous chemical and pharmacological studies over past decades because of their interesting biological activities such as cholinesterase inhibition, as well as antibacterial and antileishmanial activities. The chemical and biological properties of these alkaloids, including data relevant to straightforward structure determination and information on biosynthesis, are highlighted in this review, with 144 references being cited.
    Natural Product Reports 07/2008; 25(3):612-30. · 10.18 Impact Factor

Publication Stats

166 Citations
74.10 Total Impact Points

Institutions

  • 2004–2014
    • Tribhuvan University
      • Institute of Forestry
      Kantipura, Central Region, Nepal
  • 2008–2012
    • University of Douala
      • Faculty of Sciences
      Douala, Littoral Region, Cameroon
  • 2007–2010
    • Bielefeld University
      • Organische Chemie
      Bielefeld, North Rhine-Westphalia, Germany
  • 2006–2009
    • University of Yaoundé II
      Jaúnde, Centre Region, Cameroon
  • 2005
    • University of Karachi
      • HEJ Research Institute of Chemistry
      Karachi, Sindh, Pakistan