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11.2.2 Phenolic Compounds
Phenols and phenolic acids are best considered together since they are usually identified together during plant analysis. Free phenols are quite rare in plants. Phenolic
compounds not only possess anti-infective properties but also have anti-oxidative
properties. They are a diverse group of aromatic compounds consisting of simple
phenols and phenolic acids, flavones, flavanols and flavonoids with one carbonyl
group; quinones with two carbonyl groups; tannins and coumarins.
Phenolics in plants are mainly synthesized from the phenylpropanoid pathway.
In vitro antimicrobial activities of the phenylpropanoid pathway intermediates,
including p-coumaric acid, caffeic acid, ferulic acid and sinapic acid, and pathway
derivatives, including flavonoid aglycones and glycosides, have been demonstrated
experimentally (Barber et al. 2000). Phenolic compounds with less complex structures, such as catechol and coumarin, have also shown to exhibit bactericidal and
fungicidal activities (Cowan 1999). Syringic acid, caffeic acid and 4- hydroxybenzoic
acid were reported to have inhibitory effects on Ganoderma boninense (Chong et al.
2009). Pyrogallol and catechol are hydroxylated phenols which also show toxicity
to microorganisms.
Phenolic compounds from plants are principally modifiers of membrane protein
function. Five widely consumed phenols – curcumin (from turmeric), capsaicin
(from chilli peppers), epigallocatechin gallate (from green tea), resveratrol (from
grapes) and genistein (from soya beans) – modify lipid bilayer properties and alter
the function of diverse membrane proteins. These phytochemicals modify bilayer
properties by localizing at the bilayer/solution interface (Ingólfsson et al. 2014),
which results in their antimicrobial activity.
Curcumin, a polyphenolic compound, possesses potent antibacterial activity
against several pathogenic bacteria, including Enterococcus, Staphylococcus aureus
and S. epidermidis. It was found that curcumin induced filamentation in Bacillus
subtilis 168, suggesting that it inhibits bacterial cytokinesis. The assembly and stability of FtsZ protofilaments have been shown to play a critical role in bacterial
cytokinesis. Further, curcumin strongly inhibited the assembly of FtsZ protofilaments and also increased the GTPase activity of FtsZ. Recent developments in the
topic suggest that FtsZ may be considered as an important antibacterial drug target
where the phenolics can give better results (Dipti Rai et al. 2008a, b).
Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a type of natural phenolic compound and a phytoalexin produced by many plants in response to injury or attack by
pathogens like bacteria (Frémont 2000). It possesses antimicrobial properties
against bacteria, fungi and yeasts (Paulo et al. 2011). Resveratrol is reported to
inhibit the virulence factor expression in bacteria like Proteus mirabilis, which is an
important pathogen infecting the urinary tract, and inhibits urease activity in the
carcinogenic strain of Helicobacter pylori (Paulo et al. 2011). Due to the action of
resveratrol, FtsZ expression and Z-ring formation are suppressed, which in turn
inhibits bacterial cell growth (Hwang and Lim 2015). The major source of resveratrol is grapes and grape-derived products, including aged wine.
R. Reghu et al.
11.2.2 Phenolic Compounds
Phenols and phenolic acids are best considered together since they are usually identified together during plant analysis. Free phenols are quite rare in plants. Phenolic
compounds not only possess anti-infective properties but also have anti-oxidative
properties. They are a diverse group of aromatic compounds consisting of simple
phenols and phenolic acids, flavones, flavanols and flavonoids with one carbonyl
group; quinones with two carbonyl groups; tannins and coumarins.
Phenolics in plants are mainly synthesized from the phenylpropanoid pathway.
In vitro antimicrobial activities of the phenylpropanoid pathway intermediates,
including p-coumaric acid, caffeic acid, ferulic acid and sinapic acid, and pathway
derivatives, including flavonoid aglycones and glycosides, have been demonstrated
experimentally (Barber et al. 2000). Phenolic compounds with less complex structures, such as catechol and coumarin, have also shown to exhibit bactericidal and
fungicidal activities (Cowan 1999). Syringic acid, caffeic acid and 4- hydroxybenzoic
acid were reported to have inhibitory effects on Ganoderma boninense (Chong et al.
2009). Pyrogallol and catechol are hydroxylated phenols which also show toxicity
to microorganisms.
Phenolic compounds from plants are principally modifiers of membrane protein
function. Five widely consumed phenols – curcumin (from turmeric), capsaicin
(from chilli peppers), epigallocatechin gallate (from green tea), resveratrol (from
grapes) and genistein (from soya beans) – modify lipid bilayer properties and alter
the function of diverse membrane proteins. These phytochemicals modify bilayer
properties by localizing at the bilayer/solution interface (Ingólfsson et al. 2014),
which results in their antimicrobial activity.
Curcumin, a polyphenolic compound, possesses potent antibacterial activity
against several pathogenic bacteria, including Enterococcus, Staphylococcus aureus
and S. epidermidis. It was found that curcumin induced filamentation in Bacillus
subtilis 168, suggesting that it inhibits bacterial cytokinesis. The assembly and stability of FtsZ protofilaments have been shown to play a critical role in bacterial
cytokinesis. Further, curcumin strongly inhibited the assembly of FtsZ protofilaments and also increased the GTPase activity of FtsZ. Recent developments in the
topic suggest that FtsZ may be considered as an important antibacterial drug target
where the phenolics can give better results (Dipti Rai et al. 2008a, b).
Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a type of natural phenolic compound and a phytoalexin produced by many plants in response to injury or attack by
pathogens like bacteria (Frémont 2000). It possesses antimicrobial properties
against bacteria, fungi and yeasts (Paulo et al. 2011). Resveratrol is reported to
inhibit the virulence factor expression in bacteria like Proteus mirabilis, which is an
important pathogen infecting the urinary tract, and inhibits urease activity in the
carcinogenic strain of Helicobacter pylori (Paulo et al. 2011). Due to the action of
resveratrol, FtsZ expression and Z-ring formation are suppressed, which in turn
inhibits bacterial cell growth (Hwang and Lim 2015). The major source of resveratrol is grapes and grape-derived products, including aged wine.
R. Reghu et al.