Page 19 - Petelin, Ana. 2020. Ed. Zdravje delovno aktivne populacije / Health of the Working-Age Population. Proceedings. Koper: University of Primorska Press.
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dy, the influence of hydroxycinnamic acids such as caffeic acid, chlorogen- dietary polyphenols and their effect on the gut microbiota and human health 17
ic acid, o-coumaric acid, p-coumaric acid on the growth of a probiotic mi-
crobe (L. rhamnosus), a commensal (E. coli) and two pathogenic bacteria (S.
aureus, S. Typhimurium) was investigated. They compared the MIC values of
all polyphenols tested and observed that flavonols, isoflavones and glycosides
have low antibacterial activity, while phenolic acids were found to be at an in-
termediate level. On the other hand, the flavanone and flavanol had high anti-
bacterial activity (Parkar et al., 2008).
The effect of hydrolysable tannins (ellagitannins) on the growth of intes-
tinal bacteria is inadequately characterized, and generally their antimicrobial
potential has been assessed in vitro. It was observed that pomegranate by-prod-
ucts and punicalagins inhibited the growth of pathogenic Clostridia and S. au-
reus. Interestingly, probiotic lactobacilli and bifidobacteria were generally not
affected by ellagitannins (Bialonska et al., 2009). In this experiment, pome-
granate extract was able to increase the total bacterial number, enhancing the
growth of Bifidobacterium spp., Lactobacillus and Enterococcus groups, while
no effect was observed for the C. histolyticum group (Bialonska et al., 2010).
Resveratrol, the representative of stilbenes, increased lactobacilli and bi-
fidobacteria as well as diminished the increase of enterobacteria in in vivo stud-
ies (Larrosa et al., 2009) not representative from a dietary point of view. Our
aim was to ascertain whether resveratrol can exert anti-inflammatory activi-
ty in vivo at an attainable dietary dose. Rats were fed with 1 mg of resveratrol/
kg/day (a human equivalent dose). The results of another study showed that
resveratrol ameliorates the dysbiosis in the gut microbiota induced by the high-
fat diet, specific effects include an increase in the Bacteroidete:Firmicutes ra-
tio, significant inhibition of the growth of Enterococcus faecalis, and increased
growth of Lactobacillus and Bifidobacterium (Qiao et al., 2014).
The main limitation of the presented studies is that the information ob-
tained from in vitro studies about the role of individual phenolic compounds
on gut microbiota cannot be directly extrapolated to what occurs in the phys-
iological context of the gut ecosystem. Of those performed, most were focused
on a single polyphenol molecule and selected bacterial populations. Most phe-
nolic fractions and pure phenolic compounds have been analysed without con-
sidering the bioavailability and the chemistry of phenolic compounds in the
colon. Human and animal intervention studies involved very high doses of in-
dividual phenolic compound, or high amounts of foods rich in phenolic con-
tent, neither of which represents the regular diet (Ozdal et al., 2016). Therefore,
there is a lack of adequate in vivo studies which are needed to understand the
effect of phenolic compounds on gut microbiota. Human intervention studies
will provide the best models for studying the effect of phenolic compounds on
gut microbiota modulation. There may be a highly variable response to phenol-
ic compounds according to the differences in gut microbiota composition. Fu-
ture studies should provide answers about the inter-individual differences in
ic acid, o-coumaric acid, p-coumaric acid on the growth of a probiotic mi-
crobe (L. rhamnosus), a commensal (E. coli) and two pathogenic bacteria (S.
aureus, S. Typhimurium) was investigated. They compared the MIC values of
all polyphenols tested and observed that flavonols, isoflavones and glycosides
have low antibacterial activity, while phenolic acids were found to be at an in-
termediate level. On the other hand, the flavanone and flavanol had high anti-
bacterial activity (Parkar et al., 2008).
The effect of hydrolysable tannins (ellagitannins) on the growth of intes-
tinal bacteria is inadequately characterized, and generally their antimicrobial
potential has been assessed in vitro. It was observed that pomegranate by-prod-
ucts and punicalagins inhibited the growth of pathogenic Clostridia and S. au-
reus. Interestingly, probiotic lactobacilli and bifidobacteria were generally not
affected by ellagitannins (Bialonska et al., 2009). In this experiment, pome-
granate extract was able to increase the total bacterial number, enhancing the
growth of Bifidobacterium spp., Lactobacillus and Enterococcus groups, while
no effect was observed for the C. histolyticum group (Bialonska et al., 2010).
Resveratrol, the representative of stilbenes, increased lactobacilli and bi-
fidobacteria as well as diminished the increase of enterobacteria in in vivo stud-
ies (Larrosa et al., 2009) not representative from a dietary point of view. Our
aim was to ascertain whether resveratrol can exert anti-inflammatory activi-
ty in vivo at an attainable dietary dose. Rats were fed with 1 mg of resveratrol/
kg/day (a human equivalent dose). The results of another study showed that
resveratrol ameliorates the dysbiosis in the gut microbiota induced by the high-
fat diet, specific effects include an increase in the Bacteroidete:Firmicutes ra-
tio, significant inhibition of the growth of Enterococcus faecalis, and increased
growth of Lactobacillus and Bifidobacterium (Qiao et al., 2014).
The main limitation of the presented studies is that the information ob-
tained from in vitro studies about the role of individual phenolic compounds
on gut microbiota cannot be directly extrapolated to what occurs in the phys-
iological context of the gut ecosystem. Of those performed, most were focused
on a single polyphenol molecule and selected bacterial populations. Most phe-
nolic fractions and pure phenolic compounds have been analysed without con-
sidering the bioavailability and the chemistry of phenolic compounds in the
colon. Human and animal intervention studies involved very high doses of in-
dividual phenolic compound, or high amounts of foods rich in phenolic con-
tent, neither of which represents the regular diet (Ozdal et al., 2016). Therefore,
there is a lack of adequate in vivo studies which are needed to understand the
effect of phenolic compounds on gut microbiota. Human intervention studies
will provide the best models for studying the effect of phenolic compounds on
gut microbiota modulation. There may be a highly variable response to phenol-
ic compounds according to the differences in gut microbiota composition. Fu-
ture studies should provide answers about the inter-individual differences in
