Anti-Salmonella Agents from the Brazilian Medicinal Plant Tanacetum balsamita and their Applications - Natural Antioxidants and Biocides from Wild Medicinal Plants - page 244

prompted us to test a series of aliphatic pri-
mary alcohols (hereafter referred to simply
as alkanols) from C5 to C14 for antibacterial
activity against the same S. choleraesuis
strain. The results are listed in Table 16.3.
The range of the antibacterial activity of the
alkanols tested against this foodborne bacte-
rium is between 6.25 and 800 mg/ml, and
MICs and MBCs are markedly similar to
each other. Dodecanol was found to be the
most effective against S. choleraesuis with
an MBC of 6.25 mg/ml (34 mM), followed
by undecanol (C11) ( 11 ) with an MBC of
12.5 mg/ml (73 mM). This MBC of dodecanol
(C12) ( 12 ) is slightly more potent than that
of gentamicin. It seems that S. choleraesuis
showed different susceptibility to alkanols
possessing different chain length but, in
agreement with many other studies of the
homologous series of alkanols, the antibac-
terial activity of the alkanols against S. chol-
eraesuis increased with number of carbons
in the chain until reaching the MIC and
MBC, in this experiment at dodecanol and
undecanol, respectively. Noticeably, the
activity disappears after the chain length
reached the MIC and MBC, known as the so-
called 'cutoff' phenomenon (Balgavy and
Devínsky, 1996). For example, dodecanol
was found to be the most effective with the
MIC and MBC of 6.25 mg/ml, and the MIC
and MBC of tridecanol (C13) ( 13 ) are almost
the same as those of dodecanol but they
were variable. Tetradecanol (C14) ( 14 ) no

Table 16.2. Antibacterial activity ( m g/ml) of the
selected compounds against S. choleraesuis
subsp. choleraesuis ATCC 35640.

Compounds tested MIC MBC

2 E -Hexenal 100 100

Hexanal 400 800

Hexanol >1600 >1600

Hexanoic acid 400 400

Sorbic acid 400 400

Gentamicin 12.5 12.5

hexanoic acid ( 9 ) and sorbic acid ( 10 ) exhib-
ited the same weak activity, indicating that
the conjugated double bond in 10 is unlikely
to be related to the activity.
Although 2 E -hexenal is not the most
effective against S. choleraesuis , it was
selected to disinfect the contaminated pep-
per because of its high volatility (Wilson
and Winiewski, 1989) and broad anti-
microbial spectrum (Kubo et al ., 1995a;
Lanciotti et al ., 2003). In addition,
2 E -hexenal is the predominant volatile
component that has been found in vegeta-
tive portions of virtually all plant species
(Hatanaka, 1993) and was previously
reported to be negative for a mutagenicity
test (Andersen et al ., 1994). The pepper is
washed with 0.1% of 2 E -hexenal in etha-
nol for 3 min before the final drying pro-
cess. It may also be worthwhile considering
the anti- Salmonella activity of rather com-
mon phytochemicals from an ecological
point of view. For example, it should be
remembered that chickens used to peck
green leaves. The green leaves contain a
variety of antibacterial agents against
Salmonella bacteria, especially those
known as green leaf aldehydes and alco-
hols (Hatanaka, 1993). This indicates that
Salmonella spp. are probably controlled in
nature when chickens were continuously
fed green-leaf-based food.

Table 16.3. Antibacterial activity ( m g/ml) of
alkanols against S. choleraesuis subsp.
choleraesuis ATCC 35640.

Alkanols tested MIC MBC

C 5 >1600 >1600

C 6 >1600 >1600

C 7 800 800

C 8 400 400

C 9 200 200

C 10 50 50

C 11 12.5 12.5

C 12 6.25 6.25

16.3 Alkanols

C 13 6.25-50* 6.25-100*

C 14 >100 >100

2 E -Alkenals are highly reactive chemicals,
which may limit their practical use. This

*The values are variable.