Antibacterial activity of dipropofol and related compounds

Article abstract of DOI:10.1248/bpb.28.1120

Phenolic compounds, in general, exhibit antioxidant and antibacterial activities. We studied antimicrobial activity of the phenolic antioxidants, propofol (2,6-diisopropylphenol), tocopherol, eugenol, butylated hydroxyanisole (BHA), and several of their dimer compounds. Dipropofol (dimer of 2,6-diisopropylphenol) showed strong antibacterial activity against gram-positive strains including methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococci (VRE), while propofol and other monomeric and dimeric phenols having methyl or tert-butyl groups showed no remarkable activity. The results indicated that the dimeric structure of 2,6-diisopropylphenol moiety may play an important role in the antibacterial activity.

Full text of DOI:10.1248/bpb.28.1120

1120
Notes
Biol. Pharm. Bull. 28(6) 1120—1122 (2005)
Vol. 28, No. 6
Antibacterial Activity of Dipropofol and Related Compounds
Masahiro OGATA,*,
a,c,1)
b
a
a
a
Kanae TUTUMIMOTO SATO, Takao KUNIKANE, Kentaro OKA, Masako SEKI,
c
b
a
Shiro URANO, Keiichi HIRAMATSU, and Toyoshige ENDO
a
b
Kyoritsu University of Pharmacy; 1–5–30 Shibakoen, Minato-ku, Tokyo 105–8512, Japan: Juntendo University; 2–1–1
c
Hongo, Bunkyo-ku, Tokyo 113–8421, Japan: and Shibaura Institute of Technology; 3–9–14 Shibaura, Minato-ku, Tokyo
1
08–8548, Japan. Received January 20, 2005; accepted March 5, 2005
Phenolic compounds, in general, exhibit antioxidant and antibacterial activities. We studied antimicrobial
activity of the phenolic antioxidants, propofol (2,6-diisopropylphenol), tocopherol, eugenol, butylated hydroxy-
anisole (BHA), and several of their dimer compounds. Dipropofol (dimer of 2,6-diisopropylphenol) showed
strong antibacterial activity against gram-positive strains including methicillin resistant Staphylococcus aureus
(MRSA) and vancomycin resistant Enterococci (VRE), while propofol and other monomeric and dimeric phenols
having methyl or tert-butyl groups showed no remarkable activity. The results indicated that the dimeric struc-
ture of 2,6-diisopropylphenol moiety may play an important role in the antibacterial activity.
Key words dipropofol; antimicrobial activity; vancomycin resistant Enterococci (VRE); antioxidant; methicillin resistant
Staphylococcus aureus (MRSA)
During the past decade, nosocomial infections caused by CH Cl (10 ml) and stirred with CuCl(OH)·tetramethylethyl-
2
2
6)
methicillin-resistant Staphylococcus aureus (MRSA) in hos- enediamin (TMEDA) (16 mg) for 5 h at room temperature.
2)
pitals have become a serious clinical problem. A glycopep- The reaction product was extracted with AcOEt and the sol-
tide antibiotic, vancomycin, has been used for the treatment vent was evaporated to afford a resultant residue which was
of infections due to MRSA. Enterococci, which have some a dissolved in ethanol, and heated with Na S O (1 g) for 20
2
2
4
part of the normal faecal flora of humans and animals have min. The separated precipitate was collected on a filter and
generally emerged as important nosocomial pathogens. Ac- was crystallized from hexane to give the dimeric propofol,
quired resistance to vancomycin and teicoplanin in entero- dipropofol (950 mg, 95%) as a white solid. FAB-MS m/z:
ꢁ
1
cocci is due to the replacement of the cell wall component D- 355 (MꢁH) . H-NMR (500 MHz, CDCl , d, ppm): 1.32
3
Ala–D-Ala replaced by the depsipeptide D-Ala–D-lactate. (24H, d, Jꢂ6.7 Hz, 8ꢃCH ), 3.20 (4H, m, Jꢂ6.7 Hz, 4ꢃ
3
This substitution leads to the formation of modified peptido- CH), 7.20 (4H, s, 4ꢃH-Ar). HR-FAB-MS: 355.2643 (Calcd
glycan precursors, for which glycopeptides exhibit 1000-fold for C H O : 355.2637). mp 108 °C.
2
4
35
2
3)
lower binding affinities. In most clinical isolates of entero- Synthesis of DiBHA BHA (10 g) was dissolved in pyri-
cocci, resistance is due to acquisition for plasmids that are dine (10 g) and heated with FeSO (100 mg) and 31% H O
2
4
2
often transferable to other gram-positive bacteria by conjuga- (20 gꢃ3) at 60 °C for 30 h. The reaction product was
4)
tion. Recently, MRSA strain which has vanA gene with extracted with AcOEt and distilled by steam distillation. The
high resistance to vancomycin (minimum inhibitory concen- residue was recrystallized from ethanol to give diBHA
ꢁ
tration (MIC) ꢀ128 mg/ml), has been reported in clinical iso- (3.52 g, 35%) as a white solid. FAB-MS m/z: 359 (MꢁH) .
5
)
1
lates. Therefore, a new anti-MRSA antibiotic, which differs
H-NMR (500 MHz, CDCl , d, ppm): 1.43 (18H, s, 2ꢃtert-
3
from vancomycin in its mode of action, is clinically of interest. butyl), 3.77 (6H, s, 2ꢃOCH ), 6.60 (2H, s, H-4, 4ꢄ), 6.96
3
7)
In the course of our screening system for new anti-MRSA (2H, s, H-6, 6ꢄ). mp 223 °C.
and anti-vancomycin resistant Enterococci (VRE) antibiotics Synthesis of Di(2,6-di-t-butylphenol) 2,6-Di-t-butylphe-
from some phenolic compounds, we investigated the antibac- nol (500 mg) was dissolved in CH Cl (10 ml) and stirred
2
2
terial activity of propofol (2,6-diisopropylphenol), toco- with CuCl(OH)·TMEDA (16 mg) for 2 h at room tempera-
pherol, eugenol, butylated hydroxyanisole (BHA), and sev- ture. The reaction product was extracted with AcOEt. After
eral of their dimer compounds. Dipropofol, which is an ox- removal of solvent, the reactant was dissolved in ethanol, and
idative compound of propofol, showed inhibitory activity heated with Na S O (2 g) for 2 h. The precipitate was col-
2
2
4
against gram-positive bacteria. The present study deals with lected on a filter and crystallized from hexane to give di(2,6-
antibacterial activities of propofol, dipropofol and related di-t-butylphenol) (481 mg, 96%) as a white solid. FAB-MS
ꢁ
1
phenols.
m/z: 411 (MꢁH) . H-NMR (500 MHz, CDCl , d, ppm):
3
1
.47 (36H, s, 4ꢃtert-butyl), 5.23 (2H, s, 2ꢃ–OH), 7.36 (4H,
s, 4ꢃH-Ar). mp 112 °C.
8)
MATERIALS AND METHODS
Synthesis of Di(2,6-dimethylphenol) 2,6-Dimethylphe-
Chemicals 2,6-Di-tert-butylphenol, 2,6-dimethylphenol, nol (500 mg) was dissolved in CH Cl (10 ml) and mixed
2
2
and 2,6-diisopropylphenol (propofol) were purchased from with CuCl(OH)·TMEDA (16 mg) at room temperature at
Sigma-Aldrich Japan K.K. (Tokyo). BHA and eugenol were 5 h. The reaction product was extracted with AcOEt and
purchased from Tokyo Kasei Kogyo Co. (Tokyo). a-Toco- evaporated. The reactant was dissolved in ethanol, Na S O
2
2
4
pherol was purchased from E. Merck (Darmstadt, Germany). (2 g) was added and the mixture was heated for 2 h. The pre-
Muller-Hinton broth and agar were purchased from Nissui cipitate was collected in a filter and crystallized from hexane
Pharmaceutical Co. (Tokyo).
to give di(2,6-dimethylphenol) (462 mg, 93%) as a white
ꢁ
1
Synthesis of Dipropofol Propofol (1 g) was dissolved in solid. FAB-MS m/z: 243 (MꢁH) . H-NMR (500 MHz,
∗
To whom correspondence should be addressed. e-mail: ogata-ms@aomori-u..ac.jp
© 2005 Pharmaceutical Society of Japan

June 2005
1121
Fig. 1. Structures of Phenolic Compounds Assessed
CDCl , d, ppm): 2.10 (12H, s, 4ꢃCH ), 6.41 (2H, s, 2ꢃ Table 1. Antibacterial Activities of Phenolic Compounds against S. au-
3
3
8
)
reus, B. subtilis and E. coli
–
OH), 7.22 (4H, s, 4ꢃH-Ar). mp 118 °C.
Synthesis of Dieugenol Eugenol (10 g) was dissolved in
pyridine (10 g) and mixed with FeSO (100 mg) and 31%
Compound
S. aureus 209P B. subtilis PC219 E. coli K12
4
H O (20 gꢃ3) at 60 °C for 24 h. The reaction product was
extracted with AcOEt and distilled by steam distillation. The
a-Tocopherol
BHA
Eugenol
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
2
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
4
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
2
2
residue was recrystallized from ethanol to give dieugnol
Propofol
ꢁ
(
3.56 g, 35.6%) as a white solid. FAB-MS m/z: 327 (MꢁH) .
2,6-Dimethylphenol
1
H-NMR (500 MHz, CDCl , d, ppm): 3.33 (4H, d, Jꢂ7.3 Hz,
ꢃH-7, 7ꢄ), 3.82 (6H, s, 2ꢃOCH ), 5.06 (4H, m, Jꢂ9.8,
7.1, 1.9 Hz, 2ꢃH-9, 9ꢄ), 5.95 (2H, m, Jꢂ9.8, 17.1, 6.7 Hz,
3
2,6-Di-tert-butylphenol
DiBHA
Dieugenol
Dipropofol
Di(2,6-dimethylphenol)
2
1
3
H-8, 8ꢄ), 6.69 (2H, s, H-2, 2ꢄ), 6.74 (2H, s, H-6, 6ꢄ). mp
ꢀ128
ꢀ128
ꢀ128
9)
9
3 °C.
Antibacterial Susceptibility The minimum inhibitory
concentrations (MICs) of test compounds were determined
Di(2,6-di-tert-butylphenol) ꢀ128
by an agar double dilution method. An overnight bacterial Table 2. Antibacterial Activities of Dipropofol and Vancomycin against
6
Standard Strains
culture was diluted 100-fold (to approximately 10 cfu/ml)
and the suspension was inoculated on Muller-Hinton agar
plates prepared with each agar. The MICs were determined
after overnight culture at 37 °C.
Organism
Dipropofol
Vancomycin
10)
Staphylococcus aureus FDA 209-P
S. aureus SMITH
2
2
0.5
1
S. epidermidis IFO-12648
Micrococcus luteus ATCC-9341
Enterococcus faecalis ATCC-21212
Escherichia coli NIHJ JC-2
E. coli 445
Citrobacter freundii ATCC-8090
Proteus mirabilis IFO-3849
P. vulgaris OX-19
Morganella morganii IID KONO
Serratia marcescens IFO-12648
Enterobacter cloacae IFO-133535
E. aerogenes NCTC-10006
Pseudomonas aeruginosa 46001
P. aeruginosa E-2
2
2
2
1
0.5
2
RESULTS AND DISCUSSION
It is well known that phenolic compounds exhibit antioxi-
dant and antimicrobial activities. Propofol (2,6-diisopropy-
lphenol), a rapid, short-acting general anesthetic that is
widely employed in the induction and maintenance of anes-
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
ꢀ128
128
1
1)
thesia, has antioxidant activity, but its antimicrobial activ-
ity is unknown. We therefore studied the antibacterial activi-
ties of propofol and other phenolic compounds having an-
tioxidant activity (Fig. 1), in the phenolic compounds we
tested, only dipropofol showed antibacterial activity against
Staphylococcus aureus and Bacillus subtilis (Table 1).
Acinetobacter calcoaceticus IFO-12552 ꢀ128
Antimicrobial activities (MICs) of dipropofol were com-
pared with those of vancomycin against standard bacteria.
The results are shown in Table 2. The antibacterial spectrum
Next, we studied the antibacterial activity of dipropofol
of dipropofol was recognized against gram-positive bacteria against the antibiotic resistant strains MRSA and VRE
but not against gram-negative as vancomycin.
(Table 3). Dipropofol has strong activity against VRE (MIC

1
122
Vol. 28, No. 6
Table 3. Antibacterial Activities of Dipropofol and Vancomycin against dence, it was suggested that dipropofol seems to be a useful
MRSA and VRE
Organism
compound for a hospital infection such as Linezolid, because
of its strong antibacterial activity against VRE and MRSA.
Mechanistic studies are in progress.
Dipropofol
Vancomycin
MRSA N315 IR94
MRSA N315 IR94-HR-1
MRSA 70
E. faecalis (vanA)
E. faecium (vanA)
E. faecalis (vanB)
E. faecium (vanB)
E. gallinarum (vanC)
E. casseliflavas (vanC)
2
2
2
4
2
4
4
4
4
0.5
1
0.5
Acknowledgments We thank Kazue Kunikane, Naomi
Huse and Aki Ogata for helpful assistance. This work was
supported in part by a research grant from the KANPO Sci-
ence Foundation, Tokyo, Japan, the Ministry of Education,
Culture, Sports, Science and Technology, Japan and the New
Energy and Industrial Technology Development Organization
of Japan.
ꢀ128
ꢀ128
32
ꢀ128
16
32
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