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Extracts from 26 plant species
representing 16 families, collected in the Free State Province of South Africa,
were tested in vitro for their potential to inhibit the growth of
eight plant pathogenic fungi and five plant pathogenic bacteria. None of
the crude extracts showed any mycelial growth inhibition of the eight test
fungi. All of the extracts inhibited the growth of one or more of the five
plant pathogenic test bacteria, but to varying degrees. Crude extracts from Acacia
karroo and Elephantorrhiza elephantina inhibited the growth of
four bacteria, while that of Euclea crispa, Acacia erioloba, Senna
italica and Buddleja saligna inhibited the growth of all five
plant pathogenic bacteria. Of these, the crude extract of Euclea crispa was
clearly superior to the rest as it compared more favourably to that of a
commercial bactericide, Dimethyl Dodecyl Ammonium Chloride (DDAC). Subsequently,
the Euclea crispa crude extract was fractionated by means of liquid-liquid
extraction using four organic solvents, hexane, diethyl ether, chloroform
and ethyl acetate, in order of increasing polarity. This was done in an attempt
to assess the antimicrobial potential of the more concentrated fractions.
Once again, none of the semi-purified fractions showed any antifungal activity.
However, antibacterial activity was located in the more polar ethyl acetate
fraction indicating that the substances involved were very similar in polarity
and/or structure. From this it seems justified to further purify the ethyl
acetate fraction of the Euclea crispa extract and attempt to identify
the active substance(s) involved.

South African Journal of Botany 2002, 69(2): 186–192