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

difference in the average extract concentrations (0.06 mg/ml) (Table 5) between
acetone and methanol as extraction solvents.
The aqueous extract of B. frutescens, 0.43 mg/ml was the lowest plant extract
concentration in comparison to the other plant extracts. The acetone extract of M.
major, 2.17 mg/ml was the highest plant extract concentration (Fig. 8 and Table 5).
Melianthus major followed by Leonotis leonurus were the plants that produced the
highest average plant extract concentrations with the different solvents.
Zantedeschia aethiopica followed by Bulbine frutescens had lower plant extract
concentration yields following extraction with the different solvents (Fig. 8 and Table
5).
Following resuspension of the dried extract residues with DMSO, a 1.25% solution
was prepared from the dark coloured resuspended extracts on the day of the
microtitre plate assay. The plant extract solutions were represented in the initial,
undiluted microtitre plate wells following addition of equal amounts bacterial broth.
The less intensely coloured plant extract solutions permitted the visible and
spectrophotometric observation of bacterial growth indicated by INT in the microtitre
plates.
TABLE 5 Average concentration of the undiluted plant extracts in the microtitre
plate wells
Medicinal plants:
Average concentrations (mg/ml) of plant extracts in undiluted
microtitre plate wells:
Methanol Aqueous Acetone
Bulbine frutescens 0.51 0.43 0.51
Leonotis leonurus 1.05 1.19 1.11
Melianthus major 1.89 1.66 2.17
Zantedeschia aethiopica 1.09 0.62 1.00
Solvent average: 1.14 0.98 1.20
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