Biology Reference
In-Depth Information
E
.
coli
, which is a normal inhabitant of the human intestinal tract, or to
normal MKN-28 cells derived from gastric epithelium at concentrations
up to 50 μg/ml. Therefore, ellagitannins are potentially useful agents that
could be applied to suppress
H
.
pylori
without affecting gastric epithelial
cells and nonpathogenic intestinal bacteria.
In vivo
experiments and
studies on the mechanisms of their anti-
pylori
effect are desirable.
2.4.3 Effects on antibiotic-resistant bacteria
Studies have also unveiled the effect of polyphenolic compounds against
methicillin-resistant
Staphylococcus aureus
(MRSA), and some
ellagitannins were found to potentiate the antibacterial effect of β-lactam
antibiotics. Of the diseases caused by drug-resistant bacteria, methicillin-
resistant
S
.
aureus
(MRSA) is the one found most frequently in Japan,
and over 20,000 patients with MRSA were reported in 2005 (Infectious
Diseases Surveillance Center in Japan, 2007). The role of MRSA in
community-associated skin diseases was also shown recently (Hasty
et
al
., 2007). The MRSA strains found in hospitals have acquired resistance
not only to methicillin, but also to various antibiotics, including
aminoglycosides and macrolides (Shiota
et al
., 1999; You
et al
., 2000).
The MICs of the β-lactam antibiotic oxacillin for four MRSA strains
decreased noticeably in the presence of a small amount of (-)-
epicatechin gallate (ECG) (Shiota
et al
., 1999). An experiment
examining the effect of combining ECG and oxacillin on the bacteria
indicated that the effect was bactericidal. Additional studies on natural
medicines have shown that the ellagitannins tellimagrandin I (
114
) and
rugosin B (
11
), isolated from rose red (
i.e.
, petals of
Rosa canina
),
markedly lowered the MICs of oxacillin against the MRSA strains
(Shiota
et al
., 2000). The effect of tellimagrandin I (
114
) with oxacillin
was synergistic, and this tannin also had an analogous lowering effect on
the MICs of tetracycline for two of the four MRSA strains. Although this
tannin did not affect the MICs of aminoglycoside and macrolide
antibiotics against MRSA, the MICs of tetracycline and fosfomycin
against methicillin-sensitive
S
.
aureus
(MSSA) decreased. Corilagin (
8
),
an ellagitannin isolated from the active extract of
Arctostaphylos uva-