154 Handbook of herbs and spices
in food transit time in the gastrointestinal tract has also been observed (Platel and
Srinivasan, 2001b). Indeed, Platel and Srinivasan, (2004) record that all spices except
fenugreek and mustard shortened the food transit time. This reduction was more
prominent for ginger, ajowan, cumin, piperine, coriander and asafetida. They found
that this reduction in food transit time could probably be attributed to acceleration in
the overall digestive process as a result of increased availability of digestive enzymes
and of bile acids that facilitate fat digestion. The reduction in the whole gut transit
time caused by dietary spices probably reflects a short, post-absorptive colonic phase,
which is the longest phase of food transit, rather than that of mouth to caecum transit
phase. A reduction in colonic transit time reduces the risk and incidence of colon
cancer. Thus by reducing food transit time, spices may play a role in the prevention
of colon cancer besides combating constipation.
10.3 The effects of herbs and spices on enteric bacterial pathogens
Many herbs and spices are well established as antimicrobials (Wilkins and Board,
1989; Nychas and Tassou, 2000; Tassou et al., 2004). They possess a wide spectrum
of activity against bacteria, fungi and mycobacteria with Gram (+) being more sensitive
than Gram (–). This chapter will focus on the antimicrobial activity of herbs and
spices against pathogenic bacteria related to the gastrointestinal system such as
Helicobacter pylori, Clostridium perfringens, Escherichia coli O157:H7, Salmonella
enterica, Yersinia enterocolitica, Vibrio parahaemolyticus (Table 10.2). Consumption
of living organisms from virulent strains usually causes food-borne gastrointestinal
infections. The symptoms of gastroenteritis vary depending on the virulence of the
strain and the number of infective bacteria or the production of toxin. Bacteria adhere
to and commonly penetrate through the epithelium of intestines. Essential oils from
plants have been used traditionally for the prevention and therapy of enteric tract
infections, especially common diarrhoea.
Helicobacter pylori infection has been associated with upper gastrointestinal diseases,
such as chronic gastritis, peptic ulcer and gastric cancer (Warren, 1983; Marshall and
Warren, 1984; Parsonnet et al., 1991). The antimicrobial activity of certain herbs and
spices against H. pylori has been well investigated (Table 10.2). Indeed, the antibacterial
effect of crude garlic extracts against H. pylori has been demonstrated (Sivam et al.,
1997; Ohta et al., 1999). Other essential oils bactericidal to H. pylori in in vitro and
in vivo studies were the oils of cypress, juniper, tea tree, lemongrass, lemon verbena,
basil, peppermint, marjoram sweet, eucalyptus, ravensara, lavender, lemon, rosemary
(Ohno et al., 2003). The essential oil of the Japanese herb wasabi (Wasabia japonica,
used as a spice in traditional Japanese foods such as sashimi and sushi) has strong
antimicrobial effects against H. pylori (Shin et al., 2004). Thyme and cinnamon
extract also inhibited Helicobacter pylori at the concentration range of common
antibiotics (Tabak et al., 1996, 1999). Hydrolyzable tannins from various medicinal
plants showed promising antibacterial activity against it (Funatogawa et al., 2004) as
well as polymeric phenolics of soybean extracts (McCue et al., 2004). Katsuhiro et
al. (1999) reported that the minimum inhibitory concentration (MIC) of epigallocatechin
gallate of green tea against H. pylori was 32 mg/ml and MBC was 128 mg/ml. This
catechin showed the strongest activity of the six tea catechins tested in vitro and in
animal studies that was pH dependent (Mabe et al., 1999).