Chemistry and biological activities of Hypericum Lanceolatum

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).