Abiy Yenesew | University of Nairobi, Kenya (original) (raw)

Papers by Abiy Yenesew

Phytochemistry, Sep 1, 1998

Phytochemistry Reviews, 2002

There are several described medicinal plants in Kenya from a flora of approximately 10,000 member... more There are several described medicinal plants in Kenya from a flora of approximately 10,000 members. Strong cross-medical information from the 42 ethnic groups points to the high potential of some of these species. The Myrsinaceae are well established ethno-anthelmintics and anti-bacterials. They are harbingers of long alkyl side chain benzoquinones which clearly have a protective function from their histochemical disposition. The main benzoquinone in the sub-family Myrsinodae is embelin while for the Maesodae it is maesaquinone together with its 5-acetyl derivative; the distribution of these benzoquinones by their alkyl side chain length or the presence/absence of a 6-methyl group is in accord with morphological sub-family de-limitation. The benzoquinones showed antifeedant, anti-microbial, phytotoxic, acaricidal, insecticidal and nematicidal activity. Many other benzoquinones of medium and minor concentration were also isolated and characterised. Some plants belonging to the Polygonaceae which are widely used as ethno-anthelmintics have been studied. The common anthelmintic anthraquinones were obtained from all five Rumex species while the naphthalenic acetogenin derivative, nepodin was more selectively distributed. The leaf of Polygonum senegalense is up to 17% surface exudate; about thirteen non polar flavonoid derivatives (chalcones, dihydrochalcones, flavanones and a flavone) have been isolated from it. From the internal aerial tissues of this plant, the major flavonoids were common flavonoids, quercetin, kaempferol, luteolin and their glycosides. The only unique compound isolated from this plant was 2 -glucosyl-6 -hydroxy-4 -methoxydihydrochalcone whose aglycone, uvangolatin is part of the exudate mixture. Other leaf exudate plants studied include the stomach-ache medicine, Psiadia punctulata (Compositae) from which novel methylated flavonoids, kaurene and trachyloban diterpenes have been found.

Bulletin of the Chemical Society of Ethiopia, 2009

From the dichloromethane-methanol (1:1) extract of the seed pods of Derris trifoliata, a new flav... more From the dichloromethane-methanol (1:1) extract of the seed pods of Derris trifoliata, a new flavanone derivative (S)-lupinifolin 4´-methyl ether was isolated. In addition, the known flavonoids lupinifolin and rotenone were identified. The structures were determined on the basis of spectroscopic evidence. Lupinfolin showed moderate in vitro antiplasmodial activity against the D6 (chloroquine-sensitive) and W2 (chloroquineresistant) strains of Plasmodium falciparum. The different parts of this plant showed larvicidal activities against Aedes aegypti and rotenoids were identified as the active principles.

Phytochemistry, 2003

The dichloromethane extract of the stem bark of Millettia usaramensis subspecies usaramensis show... more The dichloromethane extract of the stem bark of Millettia usaramensis subspecies usaramensis showed anti-plasmodial activity against the chloroquine sensitive (D6) and chloroquine resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the identification of a new rotenoid, (6aR,12aS)-2,3-methylenedioxy-9-methoxy-8-(3,3-dimethylallyl)-12ahydroxyrotenoid (trivial name, usararotenoid C) along with known flavonoids (usararotenoid A, 12a-epimillettosin, 6a,12a-dehydromillettone, barbigerone and 4 0 -O-geranylisoliquiritigenin) as the anti-plasmodial principles. The structures were determined by spectroscopic analyses. CD and X-ray analyses established absolute configurations. #

Phytochemistry Letters, 2014

The stem bark extract of Schizozygia coffaeoides (Apocynaceae) showed moderate antiplasmodial act... more The stem bark extract of Schizozygia coffaeoides (Apocynaceae) showed moderate antiplasmodial activity (IC 50 = 8-12 mg/mL) against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the isolation of a new schizozygane indoline alkaloid, named 3-oxo-14a,15a-epoxyschizozygine. In addition, two dimeric anthraquinones, cassiamin A and cassiamin B, were identified for the first time in the family Apocynaceae. The structures of the isolated compounds were deduced on the basis of spectroscopic evidence. The schizozygane indole alkaloids showed good to moderate antiplasmodial activities (IC 50 = 13-52 m;).

Bulletin of the Chemical Society of Ethiopia, 2003

A new isoflavone (7,3'-dimethoxy-4',5'-methylenedioxyisoflavone) and three known isoflavones [iso... more A new isoflavone (7,3'-dimethoxy-4',5'-methylenedioxyisoflavone) and three known isoflavones [isoerythrinin A 4'-(3-methylbut-2-enyl) ether, isojamaicin and nordurlettone] were isolated from the stem bark of Millettia dura (Leguminosae). The structures were determined by spectroscopic methods.

Phytochemistry, 2000

From the stem bark of Erythrina sacleuxii two new iso¯avanones, (R)-5,7-dihydroxy-2 H ,4 H ,5 H -... more From the stem bark of Erythrina sacleuxii two new iso¯avanones, (R)-5,7-dihydroxy-2 H ,4 H ,5 H -trimethoxyiso¯avanone (trivial name, (R)-2,3-dihydro-7-demethylrobustigenin) and (R)-5-hydroxy-2 H ,4 H ,5 H -trimethoxy-2 HH ,2 HH -dimethylpyrano[5 HH ,6 HH :6,7]iso¯avanone (trivial name, (R)-saclenone) were isolated. In addition the known compounds shinpterocarpin, 2,3-dehydrokievitone, abyssinone V, abyssinone V-4 H -methyl ether, erythrinasinate and 4 H -O-methylsigmoidin B were isolated. The structures were determined on the basis of spectroscopic evidence. #

Phytochemistry, 2003

From the stem bark of Erythrina burttii, a new isoflavone, 5,2 0 ,4 0 -trihydroxy-7-methoxy-6-(3-... more From the stem bark of Erythrina burttii, a new isoflavone, 5,2 0 ,4 0 -trihydroxy-7-methoxy-6-(3-methylbut-2-enyl)isoflavone (trivial name, 7-O-methylluteone) and a new flavanone, 5,7-dihydroxy-4 0 -methoxy-3 0 -(3-methylbutadienyl)-5 0 -(3-methylbut-2-enyl)flavanone (trivial name, burttinonedehydrate) along with three known isoflavonoids (8-prenylluteone, 3-O-methylcalopocarpin and genistein) were isolated. The structures were determined on the basis of spectroscopic evidence. #

Phytochemistry, 1996

Seed pods of Millettia dura yielded four novel isoflavones, which have been characterized as 3-(3... more Seed pods of Millettia dura yielded four novel isoflavones, which have been characterized as 3-(3,4-dimethoxyphenyl)-6-methoxy-8,8-dimethyl-4H,8H-benzo[1,2-b: 3,4-b′]dipyran-4-one (trivial name, durallone), 6-demethyldurallone, 3-(3,4-dimethoxyphenyl)-8-(3-methylbut-2-enyl)-6-methoxy-7-hydroxybenzopyran-4-one (trivial name, predurallone) and 3-(4-3-methylbut-2-enyloxy)-8,8-dimethyl-4H,8H-benzo[1,2-b: 3,4-b′]dipyran-4-one (trivial name, isoerythrinin-A 4′-(3-methylbut-2-enyl) ether. Structures of these compounds were determined on the basis of their spectroscopic data.

Phytochemistry, 2004

The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activit... more The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC(50) values of 7.9+/-1.1 and 5.3+/-0.7 microg/ml, respectively. From this extract, a new chalcone, 2',3,4,4'-tetrahydroxy-5-prenylchalcone (trivial name 5-prenylbutein) and a new flavanone, 4',7-dihydroxy-3'-methoxy-5'-prenylflavanone (trivial name, 5-deoxyabyssinin II) along with known flavonoids have been isolated as the anti-plasmodial principles. The structures were determined on the basis of…

Phytochemistry Letters, 2011

Phytochemistry Letters, 2014

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.

Phytochemistry, 2005

From the acetone extract of the roots of Derris trifoliata an isoflavonoid derivative, named 7a-O... more From the acetone extract of the roots of Derris trifoliata an isoflavonoid derivative, named 7a-O-methyldeguelol, a modified rotenoid with an open ring-C, representing a new sub-class of isoflavonoids (the sub-class is here named as rotenoloid), was isolated and characterised. In addition, the known rotenoids, rotenone, deguelin and a-toxicarol, were identified. The structures were determined on the basis of spectroscopic evidence. Rotenone and deguelin were identified as the larvicidal principles of the acetone extract of the roots of Derris trifoliata.

Phytochemistry, 2002

From the root bark of Erythrina burttii three isoflav-3-enes, 7,4 0 -dihydroxy-2 0 -methoxy-6-(1 ... more From the root bark of Erythrina burttii three isoflav-3-enes, 7,4 0 -dihydroxy-2 0 -methoxy-6-(1 00 ,1 00 -dimethylallyl)isoflav-3-ene (trivial name, burttinol-A), 4 0 -hydroxy-2 0 -methoxy-2 00 ,2 00 -dimethylpyrano[5 00 ,6 00 :8,7]isoflav-3-ene (trivial name, burttinol-B), 7,4 0dihydroxy-2 0 -methoxy-8-(3 00 ,3 00 -dimethylallyl)isoflav-3-ene (trivial name, burttinol-C), and 2-arylbenzofuran, 6,4 0 -dihydroxy-2 0methoxy-5-(1 00 ,1 00 -dimethylallyl)-2-arylbenzofuran (trivial name, burttinol-D) were isolated. In addition, the known compounds, abyssinone V-4 0 -methyl ether, bidwillol A, calopocarpin, erybraedin A, erythrabyssin II, isobavachalcone, phaseollidin and phaseollin were identified. The structures were determined on the basis of spectroscopic evidence. #

Phytochemistry, Sep 1, 1998

Phytochemistry Reviews, 2002

There are several described medicinal plants in Kenya from a flora of approximately 10,000 member... more There are several described medicinal plants in Kenya from a flora of approximately 10,000 members. Strong cross-medical information from the 42 ethnic groups points to the high potential of some of these species. The Myrsinaceae are well established ethno-anthelmintics and anti-bacterials. They are harbingers of long alkyl side chain benzoquinones which clearly have a protective function from their histochemical disposition. The main benzoquinone in the sub-family Myrsinodae is embelin while for the Maesodae it is maesaquinone together with its 5-acetyl derivative; the distribution of these benzoquinones by their alkyl side chain length or the presence/absence of a 6-methyl group is in accord with morphological sub-family de-limitation. The benzoquinones showed antifeedant, anti-microbial, phytotoxic, acaricidal, insecticidal and nematicidal activity. Many other benzoquinones of medium and minor concentration were also isolated and characterised. Some plants belonging to the Polygonaceae which are widely used as ethno-anthelmintics have been studied. The common anthelmintic anthraquinones were obtained from all five Rumex species while the naphthalenic acetogenin derivative, nepodin was more selectively distributed. The leaf of Polygonum senegalense is up to 17% surface exudate; about thirteen non polar flavonoid derivatives (chalcones, dihydrochalcones, flavanones and a flavone) have been isolated from it. From the internal aerial tissues of this plant, the major flavonoids were common flavonoids, quercetin, kaempferol, luteolin and their glycosides. The only unique compound isolated from this plant was 2 -glucosyl-6 -hydroxy-4 -methoxydihydrochalcone whose aglycone, uvangolatin is part of the exudate mixture. Other leaf exudate plants studied include the stomach-ache medicine, Psiadia punctulata (Compositae) from which novel methylated flavonoids, kaurene and trachyloban diterpenes have been found.

Bulletin of the Chemical Society of Ethiopia, 2009

From the dichloromethane-methanol (1:1) extract of the seed pods of Derris trifoliata, a new flav... more From the dichloromethane-methanol (1:1) extract of the seed pods of Derris trifoliata, a new flavanone derivative (S)-lupinifolin 4´-methyl ether was isolated. In addition, the known flavonoids lupinifolin and rotenone were identified. The structures were determined on the basis of spectroscopic evidence. Lupinfolin showed moderate in vitro antiplasmodial activity against the D6 (chloroquine-sensitive) and W2 (chloroquineresistant) strains of Plasmodium falciparum. The different parts of this plant showed larvicidal activities against Aedes aegypti and rotenoids were identified as the active principles.

Phytochemistry, 2003

The dichloromethane extract of the stem bark of Millettia usaramensis subspecies usaramensis show... more The dichloromethane extract of the stem bark of Millettia usaramensis subspecies usaramensis showed anti-plasmodial activity against the chloroquine sensitive (D6) and chloroquine resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the identification of a new rotenoid, (6aR,12aS)-2,3-methylenedioxy-9-methoxy-8-(3,3-dimethylallyl)-12ahydroxyrotenoid (trivial name, usararotenoid C) along with known flavonoids (usararotenoid A, 12a-epimillettosin, 6a,12a-dehydromillettone, barbigerone and 4 0 -O-geranylisoliquiritigenin) as the anti-plasmodial principles. The structures were determined by spectroscopic analyses. CD and X-ray analyses established absolute configurations. #

Phytochemistry Letters, 2014

The stem bark extract of Schizozygia coffaeoides (Apocynaceae) showed moderate antiplasmodial act... more The stem bark extract of Schizozygia coffaeoides (Apocynaceae) showed moderate antiplasmodial activity (IC 50 = 8-12 mg/mL) against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the isolation of a new schizozygane indoline alkaloid, named 3-oxo-14a,15a-epoxyschizozygine. In addition, two dimeric anthraquinones, cassiamin A and cassiamin B, were identified for the first time in the family Apocynaceae. The structures of the isolated compounds were deduced on the basis of spectroscopic evidence. The schizozygane indole alkaloids showed good to moderate antiplasmodial activities (IC 50 = 13-52 m;).

Bulletin of the Chemical Society of Ethiopia, 2003

A new isoflavone (7,3'-dimethoxy-4',5'-methylenedioxyisoflavone) and three known isoflavones [iso... more A new isoflavone (7,3'-dimethoxy-4',5'-methylenedioxyisoflavone) and three known isoflavones [isoerythrinin A 4'-(3-methylbut-2-enyl) ether, isojamaicin and nordurlettone] were isolated from the stem bark of Millettia dura (Leguminosae). The structures were determined by spectroscopic methods.

Phytochemistry, 2000

From the stem bark of Erythrina sacleuxii two new iso¯avanones, (R)-5,7-dihydroxy-2 H ,4 H ,5 H -... more From the stem bark of Erythrina sacleuxii two new iso¯avanones, (R)-5,7-dihydroxy-2 H ,4 H ,5 H -trimethoxyiso¯avanone (trivial name, (R)-2,3-dihydro-7-demethylrobustigenin) and (R)-5-hydroxy-2 H ,4 H ,5 H -trimethoxy-2 HH ,2 HH -dimethylpyrano[5 HH ,6 HH :6,7]iso¯avanone (trivial name, (R)-saclenone) were isolated. In addition the known compounds shinpterocarpin, 2,3-dehydrokievitone, abyssinone V, abyssinone V-4 H -methyl ether, erythrinasinate and 4 H -O-methylsigmoidin B were isolated. The structures were determined on the basis of spectroscopic evidence. #

Phytochemistry, 2003

From the stem bark of Erythrina burttii, a new isoflavone, 5,2 0 ,4 0 -trihydroxy-7-methoxy-6-(3-... more From the stem bark of Erythrina burttii, a new isoflavone, 5,2 0 ,4 0 -trihydroxy-7-methoxy-6-(3-methylbut-2-enyl)isoflavone (trivial name, 7-O-methylluteone) and a new flavanone, 5,7-dihydroxy-4 0 -methoxy-3 0 -(3-methylbutadienyl)-5 0 -(3-methylbut-2-enyl)flavanone (trivial name, burttinonedehydrate) along with three known isoflavonoids (8-prenylluteone, 3-O-methylcalopocarpin and genistein) were isolated. The structures were determined on the basis of spectroscopic evidence. #

Phytochemistry, 1996

Seed pods of Millettia dura yielded four novel isoflavones, which have been characterized as 3-(3... more Seed pods of Millettia dura yielded four novel isoflavones, which have been characterized as 3-(3,4-dimethoxyphenyl)-6-methoxy-8,8-dimethyl-4H,8H-benzo[1,2-b: 3,4-b′]dipyran-4-one (trivial name, durallone), 6-demethyldurallone, 3-(3,4-dimethoxyphenyl)-8-(3-methylbut-2-enyl)-6-methoxy-7-hydroxybenzopyran-4-one (trivial name, predurallone) and 3-(4-3-methylbut-2-enyloxy)-8,8-dimethyl-4H,8H-benzo[1,2-b: 3,4-b′]dipyran-4-one (trivial name, isoerythrinin-A 4′-(3-methylbut-2-enyl) ether. Structures of these compounds were determined on the basis of their spectroscopic data.

Phytochemistry, 2004

The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activit... more The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC(50) values of 7.9+/-1.1 and 5.3+/-0.7 microg/ml, respectively. From this extract, a new chalcone, 2',3,4,4'-tetrahydroxy-5-prenylchalcone (trivial name 5-prenylbutein) and a new flavanone, 4',7-dihydroxy-3'-methoxy-5'-prenylflavanone (trivial name, 5-deoxyabyssinin II) along with known flavonoids have been isolated as the anti-plasmodial principles. The structures were determined on the basis of…

Phytochemistry Letters, 2011

Phytochemistry Letters, 2014

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.

Phytochemistry, 2005

From the acetone extract of the roots of Derris trifoliata an isoflavonoid derivative, named 7a-O... more From the acetone extract of the roots of Derris trifoliata an isoflavonoid derivative, named 7a-O-methyldeguelol, a modified rotenoid with an open ring-C, representing a new sub-class of isoflavonoids (the sub-class is here named as rotenoloid), was isolated and characterised. In addition, the known rotenoids, rotenone, deguelin and a-toxicarol, were identified. The structures were determined on the basis of spectroscopic evidence. Rotenone and deguelin were identified as the larvicidal principles of the acetone extract of the roots of Derris trifoliata.

Phytochemistry, 2002

From the root bark of Erythrina burttii three isoflav-3-enes, 7,4 0 -dihydroxy-2 0 -methoxy-6-(1 ... more From the root bark of Erythrina burttii three isoflav-3-enes, 7,4 0 -dihydroxy-2 0 -methoxy-6-(1 00 ,1 00 -dimethylallyl)isoflav-3-ene (trivial name, burttinol-A), 4 0 -hydroxy-2 0 -methoxy-2 00 ,2 00 -dimethylpyrano[5 00 ,6 00 :8,7]isoflav-3-ene (trivial name, burttinol-B), 7,4 0dihydroxy-2 0 -methoxy-8-(3 00 ,3 00 -dimethylallyl)isoflav-3-ene (trivial name, burttinol-C), and 2-arylbenzofuran, 6,4 0 -dihydroxy-2 0methoxy-5-(1 00 ,1 00 -dimethylallyl)-2-arylbenzofuran (trivial name, burttinol-D) were isolated. In addition, the known compounds, abyssinone V-4 0 -methyl ether, bidwillol A, calopocarpin, erybraedin A, erythrabyssin II, isobavachalcone, phaseollidin and phaseollin were identified. The structures were determined on the basis of spectroscopic evidence. #