| dc.description.abstract | The genus Hypericum belongs to the family Guttiferae and is represented by over 400
species. It is found widely distributed in the tropics as well as the temperate regions. This
genus is mainly characterized by the presence of xanthones, anthraquinones, fillicinic acid
and phloroglucinol acid derivatives. Presently more attention is given to this genus due to the
antiviral activity of some of its constituent compounds. It is represented by twelve species
in Eastern Africa. One of these is H. lanceolatum which is considered to be synonymous
with Hypericum revolutum by some authors, however, others consider them different taxa.
In this work the phytochemistry and biological activity of H. lanceolatum and H. revolutum
have been investigated. Based on the distribution of their constituent compounds, an attempt
has been made to determine the similarities and differences between these two taxa. The
bark, flowers and seeds of the plant samples were dried in shade, ground into powder and
then separately extracted with various solvents. This was followed by chromatographic
(column and preparative thin layer chromatography) separation with normal silica gel, silica
gel impregnated with 3% oxalic acid solution in deionized water and Sephadex LH-20
columns. The structure of the pure compounds were determined using NMR (lD and 2D),
ElMS, UV and IR spectrometers.
The hexane extract of the bark of H. revolutum afforded hyperevolutin A (4-hydroxy-8-exo
methyl-S, 7-exo-bis(3-methylbut-2-enyl)-1-(2-methyl-1-oxopropyl)-S-endo-( 4-methylpent-3enyl)bicyc1o[3.3.1]
non-3-ene 2,9-dione) (1) and the corresponding diketo form (2), while
the chloroform extract gave stigmasterol (3). The hexane and chloroform extract of the stem
bark of H. lanceolatum afforded l3 -betulinic acid (4). The combined acetone and methanol
extract of the flowers and seeds of H. lanceolatum afforded 13,IIS-biapigenin
(5,5" ,4' ,4'" ,7,7"-hexahydroxy-3,S-biflavone) (5), quercetin (3,3' ,4' ,5,7pentahydroxyflavone)
(6) and myricetin (3,3',4' ,5,5' ,7-hexahydroxyflavone) (7). | en |
