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Antimicrobial Natural phenolic compounds

 

 

Phenolic compounds are one of the most diverse groups of secondary metabolites found in edible plants.Major groups of compounds that are responsible for antimicrobial activity from plants include phenolics,phenolic acids, quinones, saponins, flavonoids, tannins, coumarins,terpenoids, and alkaloids. Phenolic compounds possess great structural variations and are one of the most diverse groups of secondary metabolites. The hydroxyl (eOH) groups in phenolic compounds are thought to cause inhibitory action as these groups can interact with the cell membrane of bacteria to disrupt membrane structures and cause the leakage of cellular components Active group such as eOH promotes the delocalization of electrons which then act as proton exchangers and reduce the gradient across the cytoplasmic membrane of bacterial cells. This will cause the collapse of the proton motive force and depletion of the ATP pool and ultimately leading to cell death. Phenolic compounds also act as antioxidants. The presence of a free eOH group in phenolic compounds results in the antioxidant properties. This property has been reported to inhibit the generation of reactive oxygen species, as well as the scavenging of free radicals thereby reducing the redox potential of the growth medium. 1

 

It was reported that an antimicrobial action of phenolic compounds was related to inactivation of cellular enzymes, which depended on the rate of penetration of the substance into the cell or caused by membrane permeability changes. Increased membrane permeability is a major factor in the mechanism of antimicrobial action, where compounds may disrupt membranes and cause a loss of cellular integrity and eventual cell death.

 

Table-1 Some phenolic compounds and their natural sources2

Compound

Structure

Source

Caffeic acid

Coffee beans, white grapes, olive,   spinach

Capsaicin

Chili peppers (septa)

Chlorogenic acid

Coffee beans, cumin, bamboo,   honeysuckle flower

Coumarin

Tonka beans, vanilla, sweet grass,   strawberries, cherries, woodruff, apricots

Curcumin

Turmeric, mustard

Decanol

Strawberries,

Ellagic acid

Berries, pomegranate, grape, walnut,   pecan

(-) Epicatechin

Tea leaves, cacao beans, cinnamon stick

Eugenol

Cinnamon, clove, nutmeg, bay leaf,   basil

Gallic acid

Grapes, gallnuts, sumac, tea leaves,   hops, oak bark

Myricetin

Berries, grapes, walnuts

Naringenin

Grapefruits, oranges

p-Coumaric   acid

Peanuts, tomatoes, carrots, garlic

Quercetin

Onions, skins of apples, citrus   fruits,cherries, fennel

Rosmarinic acid

Rosemary leaves and flowers, thyme

Rutin

Asparagus, brake fern, citrus fruits,   buckwheat

Syringic acid

Acai palm trees, swiss chard, corn

Tannic acid

Berries, nettle, tea leaves, sumac leaves,   oak wood, chestnut, gallnuts

Thymol

Thyme, nigella seeds (black cumin)

Thymoquinine

Nigella seeds (black cumin)

Xanthohumol

Female hops flowers, dandelion,   marigold

 

During food processing, oftentimes large amount of by-products are generated including fruit pomace, seeds, peels, pulps, unused flesh, and husks. Although these by-products typically have been considered waste, some studies have shown that the peels, seeds, husks and kernels are promising sources of valuable components such as phenolic compounds (polyphenols, tannins, and flavonoids) and many other bioactive components that have several functionalities including antimicrobial activity

 

Table-2 Plant by-products as antimicrobials 1

 

 

 

Reference:

1. Rabin Gyawali a, b, Salam A. Ibrahim , Natural products as antimicrobial agents, Food Control 46 (2014)  

2. Hayriye Cetin-Karaca, University of Kentucky , Master's Theses,Evaluation of natural antimicrobial phenolic compounds against foodborne pathogens