an investigation into the antibacterial activities of medicinal plants ...

methods of processing medicinal plants be taken into account when standardizing
procedures for scientific research. Ethnobotanical information revealed that all the
plants selected in this study are traditionally used fresh for medicinal purposes (Van
Wyk et al., 1997; Rabe & van Staden, 1997; Grierson & Afolayan, 1999b).
The incomplete and problematic drying of the aqueous extract supernatants in the
fume-cupboard prompted alternative drying in an incubator (37 o C) to obtain a dried
extract residue for analysis (George et al., 2001). Although many studies report on
using the respective solvents for redissolving the dried extract residues (Pillay et al.,
2001; Eloff, 1999), in this study it was found to be problematic, especially with the
use of acetone.
A visual inspection method was used for assessing the antibacterial activity of plant
extracts in studies using the respective solvents as a redissolving agent (Eloff, 1999).
However using high concentrations of extracts redissolved in acetone interfered with
the transparency of microtitre plates and the subsequent spectrophotometric analysis
of the microtitre plates in this study.
Therefore dimethylsulphoxide (DMSO) was used for redissolving the solvent-free
dried plant extract residues (Harsha et al., 2003; Nostro et al., 2000). The freshly
resuspended acetone and methanol extracts in DMSO, posed problems with
subsequent spectrophotometric analysis, due to chlorophyll interference of the dark
coloured extracts. The colour interference was circumvented with the preparation of
a 1.25% solution in distilled water of each stock DMSO plant extract.
The different chemical compositions of the plants may have contributed to the
processing of medicinal plants into fine leave particles. Leaves of Melianthus major
followed by Leonotis leonurus produced very fine leave particles in comparison to the
of Zantedeschia aethiopica that did not produce as fine leave particles after crushing
with a pestle and mortar.
The evergreen leaves of Z. aethiopica are naturally glossy which contributed to the
difficulty experienced with crushing the leaves into fine particles prior to extraction.
The glossy leaves of Z. aethiopica, failed to produce fine leave particles after trial
runs using a blender for processing the leaves. Plant material of Bulbine frutescens
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