Abiy Yenesew

Two prenylated flavanones from stem bark of Erythrina burttii

Abstract From the stem bark of Erythrina burttii , two new flavanones were isolated and characterised as 5,7-dihydroxy-4′-methoxy-3′,5′-di-(3-methylbut-2-enyl)flavanone (trivial name, abyssinone V-4′-methyl ether) and 5,7-dihydroxy-4′-methoxy-3′-(3-hydroxy-3-methylbut-1-enyl)-5′-(3-methylbut-2-enyl)flavanone (trivial name, burttinone). In addition, seven known compounds were identified. Structures were determined on the basis of spectroscopic evidence.

Rotenoids, isoflavones and chalcones from the stem bark of Millettia usaramensis subspecies usaramensis

From the stem bark of Millettia usaramensis subsp. usaramensis four new 12a-hydroxyrotenoids with the unusual trans B/C ring junction ((+)-12a-epimillettosin, (+)-usararotenoid-A, (+)-12-dihydrousararotenoid-A, and (+)-usararotenoid-B), a new α-hydroxydihydrochalcone (α,4,2′-trihydroxy-4′-O-geranyldihydrochalcone), a new isoflavone, (norisojamicin), and a new cinnamyl alcohol derivative (4-O-geranylcinnamyl acetate) have been isolated and characterized. In addition, the known compounds 4′-O-geranylisoliquiritigenin, isoliquiritigenin, barbigerone, jamaicin and maximaisoflavone-G were identified. The structures were determined on the basis of spectroscopic evidence and chemical transformations.

Chemotaxonomic significance of anthraquinones in the roots of asphodeloideae (asphodelaceae)

Abstract The distribution of seven anthraquinones in the roots of some 46 species belonging to the genera Asphodelus, Asphodeline, Bulbine, Bulbinella and Kniphofia was studied by TLC and HPLC, 1,8-Dihydroxyanthraquinones based on a chrysophanol unit are the main constituents of the subterranean metabolism in the subfamily Asphodeloideae. The genera Bulbine, Bulbinella and Kniphofia elaborate knipholone-type compounds. These compounds appear to be characteristic constituents for the three genera Bulbine, Bulbinella and Kniphofia and support the idea that Kniphofia is not related to the Alooideae.

Investigation of some medicinal plants traditionally used for treatment of malaria in Kenya as potential sources of antimalarial drugs

Malaria is a major public health problem in many tropical and subtropical countries and the burden of this disease is getting worse, mainly due to the increasing resistance of Plasmodium falciparum against the widely available antimalarial drugs. There is an urgent need for discovery of new antimalarial agents. Herbal medicines for the treatment of various diseases including malaria are an important part of the cultural diversity and traditions of which Kenyas biodiversity has been an integral part. Two major antimalarial drugs widely used today came originally from indigenous medical systems, that is quinine and artemisinin, from Peruvian and Chinese ancestral treatments, respectively. Thus ethnopharmacology is a very important resource in which new therapies may be discovered. The present review is an analysis of ethnopharmacological publications on antimalarial therapies from some Kenyan medicinal plants.

Flavonoids and isoflavonoids from Tephrosia fulvinervis and Tephrosia pentaphylla

Abstract From the roots, leaves and pods of Tephrosia pentaphylla three new 6-oxygenated rotenoids (dihydrostemonal, 9-demethyldihydrostemonal and 6-acetoxydihydrostemonal) were isolated and characterized. In addition six known rotenoids (villosin, sumatrol, rotenone, cis -12a-hydroxyrotenone, 6-hydroxyrotenone and α-toxicarol) and the flavanone obovatin were obtained. A similar analysis of the roots of T. fulvinervis yielded only known rotenoids (α-toxicarol, deguelin, munduserone, cis -12a-hydroxymunduserone) and the common pterocarpan (-)-maackiain.

FOUR ISOFLAVONES FROM SEED PODS OF MILLETTIA DURA

Abstract Seed pods of Millettia dura yielded four novel isoflavones, which have been characterized as 3-(3,4-dimethoxyphenyl)-6-methoxy-8,8-dimethyl-4 H ,8 H -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 -4 H ,8 H -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.

An anthrone, an anthraquinone and two oxanthrones from Kniphofia foliosa

Abstract The compounds isoknipholone, isoknipholone anthrone, foliosone and isofoliosone were isolated from the stem of Kniphofia foliosa and their structures determined by spectral analyses. In addition, the known compounds, aloesaponol Ill, aloesaponol III-8-methyl ether and 4,6-dihydroxy-2-methoxyacetophenone were isolated and identified.

Chemotaxonomic survey of anthraquinones and pre-anthraquinones in roots of Aloe species

Abstract Root samples from 172 species of Aloe were surveyed by TLC and HPLC for the presence of anthraquinones and pre-anthraquinones. With the exception of the three species of the series Serrulatae , 1,8-Dihydroxyanthraquinones (chrysophanol and asphodelin) were detected in all the species sampled. Compounds derived through the 1-methyl-8-hydroxyanthraquinone pathway, i.e. aloesaponarin I, aloesaponarin II and laccaic acid d -methyl ester, together with their corresponding pre-anthraquinones were detected in 129 species. The results also show that isoeleutherol is a useful chemotaxonomic character for the series Saponarieae .

Bioactive compounds from some Kenyan ethnomedicinal plants: Myrsinaceae, Polygonaceae and Psiadia punctulata

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 anti-feedant, 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.

Four isoflavones from the stem bark of erythrina sacleuxii

Abstract From the stem bark of Erythrina sacleuxii four new isoflavones were isolated and characterized as 5,7-dihydroxy-2′,4′,5′-trimethoxyisoflavone (trivial name, 7-demethylrobustigenin), 5,7-dihydroxy-4′-methoxy3′-(3-methylbut-2-enyl)isoflavone [3′-(3-methylbut-2-enyl)biochanin A], 5,7,3′-trihydroxy-4′-methoxy-5′-(3-methylbut-2-enyl)isoflavone [5′-(3-methylbut-2-enyl)pratensein] and 5,7,3′-trihydroxy-4′-methoxy-5′-formylisoflavone (5′-formylpratensein). The structures were determined on the basis of spectroscopic evidence.