11th NAPRECA Symposium Book of Proceedings, Antananarivo,
Madagascar Pages 9-19
Midiwo et al. 9
Phytochemical Evaluation of Some Kenyan Medicinal Plants
J. Ogweno Midiwo, A. Yenesew, B.F. Juma
Kerubo L Omosa, Irene L Omosa, Daniel Mutisya.
Department of Chemistry, University of Nairobi,
P.o. Box 30197,
Nairobi. Kenya.
E-mail: jmidiwo@uonbi.ac.ke
Abstract
There are more than 1200 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 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 upto 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'-methoxychalcone whose aglycone,
uvangolatin is part of the exudate mixture. Other leaf
exudate plants studied included the
stomach-ache medicine, Psiadia punctulata (Compositae) from
which novel methylated
flavonoids, kaurene and trachyloban diterpenes have been
found.
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