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

CHAPTER 5
RESULTS
Different solvent extracts of four medicinal plants (Bulbine frutescens, Leonotis
leonurus, Melianthus major & Zantedeschia aethiopica) were tested for antibacterial
activity against Gram-positive and Gram-negative bacterial strains using the
microtitre plate assay and agar dilution assay.
5.1 Microtitre plate assay
5.1.1 Undiluted plant extract concentrations
Table 5 is a representation of the average concentration of plant material extracted
from the different extraction solvents, prior to the microtitre plate assay. The freshly
processed plant material (Bulbine frutescens, Leonotis leonurus, Melianthus major &
Zantedeschia aethiopica) was extracted thrice with each extraction solvent
(methanol, aqueous & acetone) respectively. The leave gel of B. frutescens (2.5g)
extracted with the different solvents was less than the amount of leave plant material
extracted for the other three plants (5g).
The acetone solvent yielded the highest amount of plant material extracted from all
the different medicinal plants. Extraction with distilled water (aqueous) for all the
different medicinal plants produced the lowest extract concentrations in comparison
to using methanol and acetone, except for Leonotis leonurus. The aqueous extract
concentration of L. leonurus was higher than its counter methanol and acetone
extractions for L. leonurus (Table 5).
Methanol extracted similar amounts of plant material as the acetone solvent from the
different plants and produced slightly higher extract concentrations for Bulbine
frutescens and Zantedeschia aethiopica (Table 5). There was only a slight margin of
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