CHAPTER 2 LITERATURE REVIEW
4.1. Volatile extracts / essential oils
4.1.3 Antibacterial activities of the volatile extracts
4.1.3.1 Antibacterial activity of the volatile extracts of the fresh leaf, dry leaf and dry stem of T. camphoratus using the agar diffusion method
The essential oils of the fresh leaf, dry leaf and dry stem of
2010 were investigated for their antibacterial activities. The mean diameters of the zones of inhibition of the fresh leaf, dry leaf and dry stem of
The fresh leaf and dry leaf essential oils showe
and their diameters of the zones of inhibition were less than those of the standard, streptomycin. The diameters of
against Staphylococcus epidermidis
range and both essential oils showed no activity against
0 20 40 60 80 100
Percent composition
. Comparison of the essential oil constituents of T. trilobus var galpinni
of the volatile extracts
Antibacterial activity of the volatile extracts of the fresh leaf, dry leaf and dry stem using the agar diffusion method
The essential oils of the fresh leaf, dry leaf and dry stem of T.camphoratus
2010 were investigated for their antibacterial activities. The mean diameters of the zones of inhibition of the fresh leaf, dry leaf and dry stem of T. camphoratusare shown in Table The fresh leaf and dry leaf essential oils showed similar trends in their antibacterial activity and their diameters of the zones of inhibition were less than those of the standard, The diameters of the zones of inhibition of the fresh and dry leaf essential oils
dermidis, Bacillus cereus and Klebsiella pneumonia range and both essential oils showed no activity against Enterococcus faecalis
Monoterpene hydrocarbons Sesquiterpene hydrocarbons Oxygenated monoterpenes Oxygenated sesquiterpenes Others
T. trilobus var galpinni harvested
Antibacterial activity of the volatile extracts of the fresh leaf, dry leaf and dry stem
camphoratusharvested in April 2010 were investigated for their antibacterial activities. The mean diameters of the zones of are shown in Table 4.6.
in their antibacterial activity and their diameters of the zones of inhibition were less than those of the standard, inhibition of the fresh and dry leaf essential oils Klebsiella pneumoniawere in close Enterococcus faecalis, Pseudomonas
Monoterpene hydrocarbons Sesquiterpene hydrocarbons Oxygenated monoterpenes Oxygenated sesquiterpenes
aeruginosaand Shigella Shigella flexinerflexiner (Table 4.6).The dry The dry stem stem essential oil essential oil inhibited the inhibited the growth of growth of
all the tested micro-organisms with diameters of the zones of inhibition bigger than those of both the fresh and dry leaf essential oils. The dry stem essential oil also had wider inhibition zones for
essential oils showed a wider spectrum of antibacterial activity than the standard antibiotic, chloramphenicol.
Table 4.6. The antibacterial activities of the volatile extracts of the leaves and bark of T.
Camphoratususing the agar disc diffusion method.
FL DL DS S A C
5 mg/disc 2µg/disc
Micro-organism Gram- positive
Staphylococcus aureus 11.70 ±
1.20 15.00 ±
0.50 19.80 ±
0.20 18.00 ±
1.26 12.25± 0.5 0.00 Staphylococcus epidermidis 7.30 ±
0.50 7.30 ±
0.50 16.60 ±
6.90 21.00 ±
0.96 10.00± 1.2 16.33 ± 0.5 Bacillus cereus 10.30 ±
0.5 10.00 ±
0.80 20.00 ±
1.70 22.00 ±
1.71 9.25 ± 1.3 0.00 Enterococcus faecalis 0.00 0.00 13.50 ±
2.10 20.00 ±
1.29 11.0 ± 0.8 0.00 Gram-negative
Escherichia coli 12.30 ±
1.40 16.70 ±
1.40 20.40 ±
1.90 17.5 ±
1.29 12.5 ±
0.6 10.3 ±
0.5 Pseudomonas aeruginosa 0.00 0.00 20.00 ±
3.30 21.0 ±
1.71 12.0 ± 0.9 0.00 Klebsiella pneumonia 14.00 ±
0.80 13.70 ±
0.90 19.30 ±
1.20 20.0 ±
1.71 14.25 ±
0.9 13.0 ±
1.4
Shigella flexineri 0.00 0.00 17.90 ±
5.40 21.0 ±
0.82 10.0 ± 1.0 11.7 ± 1.2
Salmonella spp. 13.00 ±
1.40 10.00 ±
0.50 19.20 ±
1.60 21.0 ±
1.29 9.0 ± 0.86 17.5 ± 0.9 FL = Fresh leaves DL= Dry leaves DS = Dry stem S = Streptomycin A = Ampicillin C = Chloramphenicol
The diameters of zones of inhibition are expressed as mean ± S.D. ( n = 3);
Disc diameter = 6mm
Staphylococcus aureus and Escherichia coli than the standard drugs. All the
4.1.3.2 Antibacterial activity of the volatile extracts of the leaves and stem of T.
camphoratususing the minimum inhibition concentration (MIC) method
The MIC results, (Table 4.7), revealed that most of the bacteria showed similar susceptibility to the essential oils of the fresh leaves, dry leaves and dry stem of T. camphoratuswith an MIC value of 250 µg/ml. The least sensitive bacteria to the oils of the fresh leaves, dry leaves and dry stem was Staphylococcus aureus with an MIC value of 500 µg/ml and the lowest MIC value was shown by the dry leaf oil against Salmonella spp.
Table 4.7.Minimum inhibitory concentrations for the volatile extracts of T. camphoratus.
FL DL DS
Micro-organism Gram- positive
Staphylococcus aureus 500 500 500
Staphylococcus epidermidis 250 250 250
Bacillus cereus 250 250 250
Enterococcus faecalis ND ND 250
Gram-negative
Escherichia coli 250 250 250
Pseudomonas aeruginosa ND ND 250
Klebsiella pneumonia 250 250 250
Shigella flexineri ND ND 250
Salmonella spp. 250 125 250
FL = Fresh leaves DL= Dry leaves DS = Dry stem
4.1.3.3 Antibacterial activity of the volatile extract of the fresh leaf of T.trilobus var galpinniusing the agar disc diffusion and minimum inhibition concentration (MIC) method.
The results for the diameters of the zones of inhibition and the minimum inhibitory concentration (MIC) of the essential oil of the fresh leaf of T. trilobus var galpinniagainst the tested micro-organisms are shown in Table 4.8. The essential oil did not show antibacterial
activity against Enterococcus faecalis and Pseudomonas aeruginosa whereas it showed higher inhibition against Escherichia coli, Klebsiella pneumonia, Bacillus cereusand Shigella flexineri than the reference drugs, chloramphenical and ampicillin. The MIC values ranged between 31.25 and 250 µg/ml, the most sensitive bacteria with the lowest MIC value of 31.25 µg/ml was Klebsiella pneumonia and the least sensitive bacteria was Staphylococcus epidermidiswith an MIC value of 250 µg/ml.
Table 4.8. The mean diameters in mm of the zones of inhibition and the MIC value of the volatile extract of the fresh leaf of T.trilobus var galpinni.
Zone of inhibition MIC (µg/ml)
FL S A C FL
Micro-organism Gram- positive Staphylococcus
aureus 9.13 ± 0.85 18.00 ± 1.26 12.25 ± 0.5 0.00 125
Staphylococcus
epidermidis 8.23 ± 0.22 21.00 ± 0.96 10.0 ± 1.2 16.33 ± 0.5 250 Bacillus cereus 19.00 ± 2.58 22.00 ± 1.71 9.25 ± 1.3 0.00 ND Enterococcus faecalis 0.00 20.00 ± 1.29 11.0 ± 0.8 0.00 ND Gram-negative
Escherichia coli 19.50 ± 1.96 17.5 ± 1.29 12.5 ± 0.6 10.3 ± 0.5 125 Pseudomonas
aeruginosa 0.00 21.0 ± 1.71 12.0 ± 0.9 0.00 ND
Klebsiella pneumonia 14.50 ± 2.87 20.0 ± 1.71 14.25 ± 0.9 13.0 ± 1.4 31.25 Shigella flexineri 21.75 ± 1.71 21.0 ± 0.82 10.0 ± 1.0 11.7 ± 1.2 62.5 Salmonella spp. 7.88 ± 0.62 21.0 ± 1.29 9.0 ± 0.86 17.5 ± 0.9 125
FL = Fresh leaf A = Ampicillin C = Chloramphenicol S = Streptomycin The diameters of zones of inhibition are expressed as mean ± S.D. ( n = 3);
Disc diameter = 6mm
4.1.3.4 Comparison of the antibacterial activity of the fresh leaf oil of T. trilobus var galpinniwith the essential oils of the leaf and stem of T. camphoratus
Comparing the diameters of the zones of inhibition, the essential oil of T. trilobus var galpinni showed weaker antibacterial activity against Staphylococcus aureusand Salmonella spp than all the essential oils of T. camphoratusbut showed stronger activity against Bacillus cereus, Escherichia coliand Klebsiella pneumoniathan the fresh and dry leaf essential oils of
against Shigella flexineri and its inhibition against Escherichia coli and Bacillus cereus was comparable to that of the dry stem essential oil of T. camphoratus. There was no significant difference in the means of the diameters of the zones of inhibition at p = > 0.05 of the essential oils of the fresh leaf and dry leaf of T. camphoratus, the essential oil of T. trilobus var galpinni, ampicillin and chloramphenicol but there was a significant difference at p = <
0.05, in the diameters of the zones of inhibition between the fresh leaf essential oil of T.
camphoratus, the dry leaf essential oil of T. camphoratus, chloramphenical and the dry stem essential oil of T. camphoratus. The action of the dry stem essential oil was comparable to that of the standard drugs, streptomycin and ampicillin. Considering MIC values, the essential oil of the fresh leaf of T. trilobus var galpinni generally showed lower MIC values hence higher activity than the essential oils of T. camphoratus when tested on similar micro-organisms.