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

Undiluted plant extract concentrations
2.5
Extract concentrations (mg/ml)
2
1.5
1
0.5
0
Methanol
Aqueous
Acetone
B. frutescens
L. leonurus
M. major
Z. aethiopica
FIGURE 8
Plant extract concentrations in the undiluted microtitre plate wells
5.1.2 Visible representation of MIC’s in the microtitre plates
The bacterial growth in the microtitre plates were indicated and detected with the use
of a bacterial growth indicator, INT. Spectrophotometric readings of the microtitre
plates before and after the addition of INT facilitated the analysis of antibacterial
activity of the plant extracts.
The INT indicates the presence of viable bacteria in the microtitre plate suspensions
by acting as an electron acceptor for the bacteria to form a red-coloured formazan
product (Figure 9). After INT addition and incubation of the microtitre plates the
presence of antibacterial activity could be assessed with the naked eye (Figure 9).
Antibacterial activity was indicated by the absence of the red-coloured formazan
product in microtitre plate suspensions (Figure 9).
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