Summary of MIC Values of Phytoalexin and Phytoncide Against MRSA and VRE
The MIC values of phytoalexin and phytoncide against MRSA and VRE are sum-
marized in Tables 7.7 and 7.8.
146 7 Anti-MRSA and Anti-VRE Activities of Phytoalexins and Phytoncides Isolated from Tropical Plants
Table 7.6 MIC values of gnemonol B and gnetin E against nine strains of methicillin-resistant
S. aureus (MRSA) and three strains of methicillin-sensitive S. aureus (MSSA).
MIC (μg mL–1)
Gnemonol B Gnetin E Gentamicin
MRSA-1[a] 6.25 12.5 25
MRSA-2[a] 6.25 12.5 3.13
MRSA-3[a] 6.25 25 1.56
MRSA-4[b] 6.25 12.5 3.13
MRSA-5[b] 6.25 12.5 6.25
MRSA-6[b] 6.25 12.5 0.2
MRSA-7[c] 6.25 12.5 0.2
MRSA-8[c] 6.25 25 6.25
MRSA-9[c] 6.25 25 >100
MSSA 1 (S. aureus IFO 13276)[d] 6.25 12.5 0.2
MSSA 2 (S. aureus IFO 12732)[d] 6.25 12.5 0.2
MSSA 3 (S. aureus IFO 3080)[d] 6.25 12.5 0.2
MIC, minimum inhibitory concentration.
a Donated from Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan.
b Donated from Osaka National Hospital, Japan.
c Donated from Kitano Hospital, Japan.
d Purchased from Institute for Fermentation of Osaka (IFO), Japan.
Table 7.7 Anti-VRE activities of sophoraflavanone G, calozeyloxanthone,
-mangostin and stilbene oligomers.
MIC (μg mL–1)
Sophoraflavanone G 6.25–12.5
Calozeyloxanthone 6.25–12.5
-Mangostin 3.13–6.25
Gnemonol B 12.5
Gnetin E 12.5–25
Gentamicin 6.25–400
MIC, minimum inhibitory concentration.
Sophoraflavanone G, calozeyloxanthone, and -mangostin possessed strong anti-
MRSA and anti-VRE activities compared with gentamicin. Stilbene oligomers (gnem-
onol B and gnetin E) also possessed anti-MRSA and anti-VRE activities, but they were
weaker than those of sophoraflavanone G, calozeyloxanthone, and -mangostin.
7.9
Synergism Between the Test Compounds and Commercial Antibiotics Against VRE,
MRSA, VSE, and MSSA
7.9.1
Sophoraflavanone G
Synergism between sophoraflavanone G and vancomycin hydrochloride or fos-
fomycin was observed (FIC indices were 0.16 and 0.48), while partial synergism
was seen between sophoraflavanone G and other antibacterial agents such as am-
picillin, gentamicin, and minocycline (FIC indices were 0.73, 0.69, and 0.65, re-
spectively) (Fig. 7.5).
7.9 Synergism Between the Test Compounds and Commercial Antibiotics 147
Table 7.8 Anti-MRSA activities of sophoraflavanone G, calozeyloxanthone,
-mangostin and stilbene oligomers.
MIC (μg mL–1)
Sophoraflavanone G 3.13–6.25
-Mangostin 6.25–12.5
Gnemonol B 6.25
Gnetin E 12.5–25
Gentamicin 1.56–100
MIC, minimum inhibitory concentration.
Fig. 7.5 Synergisms between sophoraflavanone G and commercially available antibiotics.
FIC, fraction inhibitory concentration; ABPC, ampicillin; GM, gentamicin; MINO, minocycline;
FOM, fosfomycin; VCM, vancomycin; MRSA, methicillin-resistant Staphylococcus aureus.
7.9.2
Calozeyloxanthone
A marked synergism between calozeyloxanthone and vancomycin hydrochloride
against VRE was observed, as shown as Fig. 7.6. The FIC index of calozeyloxan-
thone and commercially available antibiotics such as ampicillin, gentamicin, mi-
nocycline, and vancomycin hydrochloride against VRE were 0.750, 0.625, 0.563,
and 0.453, respectively.
148 7 Anti-MRSA and Anti-VRE Activities of Phytoalexins and Phytoncides Isolated from Tropical Plants
Fig. 7.6 Synergism between calozeyloxanthone and the commercially available
antibiotics against each of two strains of vancomycin-resistant enterococci (VRE)
and vancomycin-sensitive enterococci (VSE). FIC, fraction inhibitory concentration;
ABPC, ampicillin; GM, gentamicin; MINO, minocycline; VCM, vancomycin.
7.9.3
-Mangostin
The result is given in Fig. 7.7. Synergism between -mangostin and gentamicin
against VRE, and -mangostin and vancomycin hydrochloride against MRSA was
also observed. In the above synergistic studies, the average of FIC index was calcu-
lated as 0.451±0.069 and 0.441±0.131, respectively. Partial synergism between -
mangostin and ampicillin, minocycline, fosfomycin, and vancomycin hydrochlo-
ride against VRE with FIC indices of 0.606±0.328, 0.969±0.217, 0.826±0.286, and
0.508±0.271 were observed, respectively.
Furthermore, partial synergisms between -mangostin and ampicillin, gentam-
icin, minocycline, and vancomycin hydrochloride against MRSA were also ob-
served, and their FIC indices were calculated as 0.779±0.343, 0.667±0.359,
0.586±0.303, and 0.504±0.149, respectively.
On VSE, synergism between -mangostin and vancomycin hydrochloride was
observed, and the FIC index was calculated to be 0.378±0.113. Partial synergisms
between -mangostin and the commercially available antibiotics ampicillin, gen-
tamicin, minocycline, and fosfomycin were observed, and their FIC indices were
calculated as 0.836±0.284, 0.500±0.108, 0.750±0.000, and 0.792±0.191, respec-
tively.
On MSSA, FIC indices between -mangostin and the commercially available
antibiotics ampicillin, gentamicin, minocycline, fosfomycin, and vancomycin hy-
drochloride were observed, and their FIC indices were calculated as 0.635±0.325,
0.428±0.209, 0.750±0.000, 0.625±0.217, and 0.625±0.000, respectively.
Synergism between -mangostin and gentamicin against five strains of VRE,
and -mangostin and vancomycin hydrochloride against nine strains of MRSA
were also tested by the evaluation method described by Williamson [29]. The re-
sults are shown in Figs 7.8 and 7.9, respectively. Synergism between -mangostin
and gentamicin against VRE, and -mangostin and vancomycin hydrochloride
against MRSA were reconfirmed by this method.
7.9 Synergism Between the Test Compounds and Commercial Antibiotics 149
Fig. 7.7 Synergism between -mangostin and antibiotics against vancomycinresistant
enterococci (VRE), methicillin-resistant Staphylococcus aureus
(MRSA), vancomycin-sensitive enterococci (VSE), and methicillin-sensitive
Staphylococcus aureus (MSSA).
150 7 Anti-MRSA and Anti-VRE Activities of Phytoalexins and Phytoncides Isolated from Tropical Plants
Fig. 7.8 Synergism between -mangostin and gentamicin against five strains
of vancomycin-resistant enterococci (VRE).
Fig. 7.9 Synergism between -mangostin and vancomycin hydrochloride
against nine strains of methicillin-resistant Staphylococcus aureus (MRSA).
7.9.4
Stilbene Oligomer
The results of synergisms of gnemonol B or gnetin E with the commercially avail-
able antibiotics against VRE, MRSA, VSE, and MSSA are shown in Figs 7.10 and
7.11, respectively.
7.9 Synergism Between the Test Compounds and Commercial Antibiotics 151
Fig. 7.10 Synergism between gnemonol B and antibiotics against vancomycinresistant
enterococci (VRE), methicillin-resistant Staphylococcus aureus
(MRSA), vancomycin-sensitive enterococci (VSE), and methicillin-sensitive
Staphylococcus aureus (MSSA).
Gnemonol B exhibited a partial synergistic effect in combination with ampicil-
lin, gentamicin, minocycline, fosfomycin, and vancomycin hydrochloride against
VRE. It also showed a partial synergism with gentamicin against MRSA. The aver-
age of FIC indices against VRE were calculated as 0.703±0.105, 0.550±0.068,
0.678±0.106, 0.763±0.155, and 0.624±0.169. The FIC indices of gnemonol B with
ampicillin, gentamicin, minocycline, fosfomycin, and vancomycin hydrochloride
against MRSA were also calculated as 0.708±0.072, 0.501±0.249, 0.833±0.144,
0.750±0.000, and 0.750±0.000, respectively (Fig. 7.10).
In combination of gnemonol B with ampicillin, gentamicin, minocycline,
fosfomycin, and vancomycin hydrochloride, partial synergism against VSE was
exhibited, and the FIC indices were calculated as 0.836±0.284, 0.500±0.108,
0.750±0.000, 0.500±0.108, and 0.792±0.191, respectively.
Synergism of gnemonol B with gentamicin was observed against MSSA (FIC in-
dex 0.719±0.248). FIC indices of the other antibiotics such as ampicillin, minocy-
cline, fosfomycin, and vancomycin hydrochloride were calculated as 1.323±0.332,
0.918±0.306, 1.085±0.124, 1.089±0.121, and 1.403±0.285 (Fig. 7.10).
Partial synergism of gnetin E with gentamicin and vancomycin hydrochloride
against VRE, and of gnetin E with gentamicin, minocycline, fosfomycin, and van-
comycin hydrochloride against MRSA were observed, respectively. The FIC indi-
ces of gnetin E with gentamicin and vancomycin hydrochloride on VRE were
0.770±0.229 and 0.746±0.248, respectively. The FIC indices of gnetin E with am-
picillin, gentamicin, minocycline, fosfomycin, and vancomycin hydrochloride on
MRSA were 1.195±0.369, 0.667±0.107, 0.913±0.317, 0.809±0.264, and 0.854±
0.203, respectively.
152 7 Anti-MRSA and Anti-VRE Activities of Phytoalexins and Phytoncides Isolated from Tropical Plants
Fig. 7.11 Synergism between gnetin E and antibiotics against vancomycin-resistant
enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), vancomycinsensitive
enterococci (VSE), and methicillin-sensitive Staphylococcus aureus (MSSA).
Partial synergism of gnetin E in combination with ampicillin, gentamicin, and
fosfomycin against VSE were observed, and the FIC indices were 0.705±0.261,
0.750±0.000, and 0.698±0.289.
Against MSSA, the FIC indices of gnetin E in combination with ampicillin, gen-
tamicin, minocycline, fosfomycin, and vancomycin hydrochloride were 1.667±
0.577, 0.594±0.054, 1.333±0.144, 1.130±0.117, and 1.083±0.289 (Fig. 7.11).
7.9.5
The MIC values of phytoalexin and phytoncide against MRSA and VRE are sum-
marized in Tables 7.7 and 7.8.
146 7 Anti-MRSA and Anti-VRE Activities of Phytoalexins and Phytoncides Isolated from Tropical Plants
Table 7.6 MIC values of gnemonol B and gnetin E against nine strains of methicillin-resistant
S. aureus (MRSA) and three strains of methicillin-sensitive S. aureus (MSSA).
MIC (μg mL–1)
Gnemonol B Gnetin E Gentamicin
MRSA-1[a] 6.25 12.5 25
MRSA-2[a] 6.25 12.5 3.13
MRSA-3[a] 6.25 25 1.56
MRSA-4[b] 6.25 12.5 3.13
MRSA-5[b] 6.25 12.5 6.25
MRSA-6[b] 6.25 12.5 0.2
MRSA-7[c] 6.25 12.5 0.2
MRSA-8[c] 6.25 25 6.25
MRSA-9[c] 6.25 25 >100
MSSA 1 (S. aureus IFO 13276)[d] 6.25 12.5 0.2
MSSA 2 (S. aureus IFO 12732)[d] 6.25 12.5 0.2
MSSA 3 (S. aureus IFO 3080)[d] 6.25 12.5 0.2
MIC, minimum inhibitory concentration.
a Donated from Osaka Medical Center for Cancer and Cardiovascular Diseases, Japan.
b Donated from Osaka National Hospital, Japan.
c Donated from Kitano Hospital, Japan.
d Purchased from Institute for Fermentation of Osaka (IFO), Japan.
Table 7.7 Anti-VRE activities of sophoraflavanone G, calozeyloxanthone,
-mangostin and stilbene oligomers.
MIC (μg mL–1)
Sophoraflavanone G 6.25–12.5
Calozeyloxanthone 6.25–12.5
-Mangostin 3.13–6.25
Gnemonol B 12.5
Gnetin E 12.5–25
Gentamicin 6.25–400
MIC, minimum inhibitory concentration.
Sophoraflavanone G, calozeyloxanthone, and -mangostin possessed strong anti-
MRSA and anti-VRE activities compared with gentamicin. Stilbene oligomers (gnem-
onol B and gnetin E) also possessed anti-MRSA and anti-VRE activities, but they were
weaker than those of sophoraflavanone G, calozeyloxanthone, and -mangostin.
7.9
Synergism Between the Test Compounds and Commercial Antibiotics Against VRE,
MRSA, VSE, and MSSA
7.9.1
Sophoraflavanone G
Synergism between sophoraflavanone G and vancomycin hydrochloride or fos-
fomycin was observed (FIC indices were 0.16 and 0.48), while partial synergism
was seen between sophoraflavanone G and other antibacterial agents such as am-
picillin, gentamicin, and minocycline (FIC indices were 0.73, 0.69, and 0.65, re-
spectively) (Fig. 7.5).
7.9 Synergism Between the Test Compounds and Commercial Antibiotics 147
Table 7.8 Anti-MRSA activities of sophoraflavanone G, calozeyloxanthone,
-mangostin and stilbene oligomers.
MIC (μg mL–1)
Sophoraflavanone G 3.13–6.25
-Mangostin 6.25–12.5
Gnemonol B 6.25
Gnetin E 12.5–25
Gentamicin 1.56–100
MIC, minimum inhibitory concentration.
Fig. 7.5 Synergisms between sophoraflavanone G and commercially available antibiotics.
FIC, fraction inhibitory concentration; ABPC, ampicillin; GM, gentamicin; MINO, minocycline;
FOM, fosfomycin; VCM, vancomycin; MRSA, methicillin-resistant Staphylococcus aureus.
7.9.2
Calozeyloxanthone
A marked synergism between calozeyloxanthone and vancomycin hydrochloride
against VRE was observed, as shown as Fig. 7.6. The FIC index of calozeyloxan-
thone and commercially available antibiotics such as ampicillin, gentamicin, mi-
nocycline, and vancomycin hydrochloride against VRE were 0.750, 0.625, 0.563,
and 0.453, respectively.
148 7 Anti-MRSA and Anti-VRE Activities of Phytoalexins and Phytoncides Isolated from Tropical Plants
Fig. 7.6 Synergism between calozeyloxanthone and the commercially available
antibiotics against each of two strains of vancomycin-resistant enterococci (VRE)
and vancomycin-sensitive enterococci (VSE). FIC, fraction inhibitory concentration;
ABPC, ampicillin; GM, gentamicin; MINO, minocycline; VCM, vancomycin.
7.9.3
-Mangostin
The result is given in Fig. 7.7. Synergism between -mangostin and gentamicin
against VRE, and -mangostin and vancomycin hydrochloride against MRSA was
also observed. In the above synergistic studies, the average of FIC index was calcu-
lated as 0.451±0.069 and 0.441±0.131, respectively. Partial synergism between -
mangostin and ampicillin, minocycline, fosfomycin, and vancomycin hydrochlo-
ride against VRE with FIC indices of 0.606±0.328, 0.969±0.217, 0.826±0.286, and
0.508±0.271 were observed, respectively.
Furthermore, partial synergisms between -mangostin and ampicillin, gentam-
icin, minocycline, and vancomycin hydrochloride against MRSA were also ob-
served, and their FIC indices were calculated as 0.779±0.343, 0.667±0.359,
0.586±0.303, and 0.504±0.149, respectively.
On VSE, synergism between -mangostin and vancomycin hydrochloride was
observed, and the FIC index was calculated to be 0.378±0.113. Partial synergisms
between -mangostin and the commercially available antibiotics ampicillin, gen-
tamicin, minocycline, and fosfomycin were observed, and their FIC indices were
calculated as 0.836±0.284, 0.500±0.108, 0.750±0.000, and 0.792±0.191, respec-
tively.
On MSSA, FIC indices between -mangostin and the commercially available
antibiotics ampicillin, gentamicin, minocycline, fosfomycin, and vancomycin hy-
drochloride were observed, and their FIC indices were calculated as 0.635±0.325,
0.428±0.209, 0.750±0.000, 0.625±0.217, and 0.625±0.000, respectively.
Synergism between -mangostin and gentamicin against five strains of VRE,
and -mangostin and vancomycin hydrochloride against nine strains of MRSA
were also tested by the evaluation method described by Williamson [29]. The re-
sults are shown in Figs 7.8 and 7.9, respectively. Synergism between -mangostin
and gentamicin against VRE, and -mangostin and vancomycin hydrochloride
against MRSA were reconfirmed by this method.
7.9 Synergism Between the Test Compounds and Commercial Antibiotics 149
Fig. 7.7 Synergism between -mangostin and antibiotics against vancomycinresistant
enterococci (VRE), methicillin-resistant Staphylococcus aureus
(MRSA), vancomycin-sensitive enterococci (VSE), and methicillin-sensitive
Staphylococcus aureus (MSSA).
150 7 Anti-MRSA and Anti-VRE Activities of Phytoalexins and Phytoncides Isolated from Tropical Plants
Fig. 7.8 Synergism between -mangostin and gentamicin against five strains
of vancomycin-resistant enterococci (VRE).
Fig. 7.9 Synergism between -mangostin and vancomycin hydrochloride
against nine strains of methicillin-resistant Staphylococcus aureus (MRSA).
7.9.4
Stilbene Oligomer
The results of synergisms of gnemonol B or gnetin E with the commercially avail-
able antibiotics against VRE, MRSA, VSE, and MSSA are shown in Figs 7.10 and
7.11, respectively.
7.9 Synergism Between the Test Compounds and Commercial Antibiotics 151
Fig. 7.10 Synergism between gnemonol B and antibiotics against vancomycinresistant
enterococci (VRE), methicillin-resistant Staphylococcus aureus
(MRSA), vancomycin-sensitive enterococci (VSE), and methicillin-sensitive
Staphylococcus aureus (MSSA).
Gnemonol B exhibited a partial synergistic effect in combination with ampicil-
lin, gentamicin, minocycline, fosfomycin, and vancomycin hydrochloride against
VRE. It also showed a partial synergism with gentamicin against MRSA. The aver-
age of FIC indices against VRE were calculated as 0.703±0.105, 0.550±0.068,
0.678±0.106, 0.763±0.155, and 0.624±0.169. The FIC indices of gnemonol B with
ampicillin, gentamicin, minocycline, fosfomycin, and vancomycin hydrochloride
against MRSA were also calculated as 0.708±0.072, 0.501±0.249, 0.833±0.144,
0.750±0.000, and 0.750±0.000, respectively (Fig. 7.10).
In combination of gnemonol B with ampicillin, gentamicin, minocycline,
fosfomycin, and vancomycin hydrochloride, partial synergism against VSE was
exhibited, and the FIC indices were calculated as 0.836±0.284, 0.500±0.108,
0.750±0.000, 0.500±0.108, and 0.792±0.191, respectively.
Synergism of gnemonol B with gentamicin was observed against MSSA (FIC in-
dex 0.719±0.248). FIC indices of the other antibiotics such as ampicillin, minocy-
cline, fosfomycin, and vancomycin hydrochloride were calculated as 1.323±0.332,
0.918±0.306, 1.085±0.124, 1.089±0.121, and 1.403±0.285 (Fig. 7.10).
Partial synergism of gnetin E with gentamicin and vancomycin hydrochloride
against VRE, and of gnetin E with gentamicin, minocycline, fosfomycin, and van-
comycin hydrochloride against MRSA were observed, respectively. The FIC indi-
ces of gnetin E with gentamicin and vancomycin hydrochloride on VRE were
0.770±0.229 and 0.746±0.248, respectively. The FIC indices of gnetin E with am-
picillin, gentamicin, minocycline, fosfomycin, and vancomycin hydrochloride on
MRSA were 1.195±0.369, 0.667±0.107, 0.913±0.317, 0.809±0.264, and 0.854±
0.203, respectively.
152 7 Anti-MRSA and Anti-VRE Activities of Phytoalexins and Phytoncides Isolated from Tropical Plants
Fig. 7.11 Synergism between gnetin E and antibiotics against vancomycin-resistant
enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), vancomycinsensitive
enterococci (VSE), and methicillin-sensitive Staphylococcus aureus (MSSA).
Partial synergism of gnetin E in combination with ampicillin, gentamicin, and
fosfomycin against VSE were observed, and the FIC indices were 0.705±0.261,
0.750±0.000, and 0.698±0.289.
Against MSSA, the FIC indices of gnetin E in combination with ampicillin, gen-
tamicin, minocycline, fosfomycin, and vancomycin hydrochloride were 1.667±
0.577, 0.594±0.054, 1.333±0.144, 1.130±0.117, and 1.083±0.289 (Fig. 7.11).
7.9.5
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