Phenolic acids is a group of organic compound with carboxyl group attached to a phenol ring. It is a heterogeneous group of substances that act and are like both vital plants and human bodies. They are strong antioxidants that are used in skin treatments. They are found in various plant derived foods such as apple, kale, berries etc. In this article, we will discuss the common features, incidence, properties, uses, and prospects of these compounds.

What is Phenolic Acid?

Phenolic acids are a class of organic compounds that contain a phenolic ring (an aromatic ring with one or more hydroxyl groups) and a carboxylic acid functional group. They are also called phenol carboxylic acids. These compounds are derivatives of benzoic acid or cinnamic acid and are commonly found in plants, where they serve various biological functions.

Phenolic Acid Formula

The chemical formula of phenolic acids is C₆H₅OHCOOH

Phenolic Acid Structure

Phenolic Acid contains the two groups of phenolic ring (C6H5OH) and the carboxylic acid (COOH) group. The structure of phenolic acid is given below:

Occurrence of Phenolic Acids

Phenyl acid is a generalized name that occurs throughout the plant kingdom, and it can be found in leaves, stems, roots, fruits, and seeds. It is formed from the shikimic acid pathway, a unique metabolic pathway from plants, bacteria, and fungi.

Plant derived foods such as fruits, vegetables, grains and their derived products are significant sources of phenolic acids thus they are important constituents of our diet.

Fruits: A variety of berries (e.g. strawberries, blueberries, raspberries, and blackberries.) plus citrus fruits (lemons, oranges, and grapefruits) and apples, grapes, cherries and pomegranates are good sources of vitamin C.

Vegetables: Spinach, kale, broccoli, onions, garlic, artichokes, and tomatoes. Sunlight is the basic condition for their growth.

Whole Grains: Wheat, oats, barley, rye, and whole grain sources.

Nuts and Seeds: Almonds, walnuts, flaxseeds and chia seeds, and sesame seeds.

Beverages: Tooth enamel wears out because of constant acid exposure from coffee, tea (green tea and black tea), red wine and fruit juices.

Herbs and Spices: Sticks of cinnamon, cloves, oregano, thyme, and rosemary.

The concentration of phenolic acids in plants can vary due to the same may affect the plant species, cultivar, ripeness, and growing conditions, as well as the way after harvesting are processed. Another example would be the phenolic acid concentration in fruits, which increases as they mature but then gets reduced during fruit ripening.

Types of Phenolic Acids

Phenolic Acids can be classified into two main groups based on their chemical structure:

Hydroxybenzoic Acids:

Hydroxybenzoic acids are ether portion of benzoic acids and mostly have one hydroxyl group (-OH) located on the benzene ring. Some of the common hydroxybenzoic acids include:

Gallic Acid: It is well known by another name of 3,4,5-trihydroxybenzoic acid that exists in not only in plants but also in some fruits, such as grapes, strawberries, and blueberries.

Protocatechuic Acid: 3,4-dihydroxybenzoic acid, known as protocatechuic acid, is in the natural occurring products for example, vegetables, fruits and the green tea.

Vanillic Acid: Vanillic acid is the methyl ester of gallic acid with additional methoxyl group that is commonly found dietary supplements, including, for example, vanilla beans, fruits and coffee.

Hydroxycinnamic Acids

Hydroxycinnamic acids are the types in cinnamic acid which contains a hydroxyl group (-OH) attached to the benzene ring. Some of the examples of hydroxycinnamic acids are:

Caffeic Acid: Widely found in plants, like legumes, caffeic acid is the most abundantly available source of such food items as coffee, fruits, vegetables, and grains.

Ferulic Acid: Ferulic acid is a common component of fruits, vegetables, whole grains, and seeds. These are especially abundant in wheat bran and rice bran owing to their higher concentration.

P-Coumaric Acid: In the human diet, P-Coumaric acid is mostly present in those plants; fruits, vegetables, grains and spices are the best examples.

Properties of Phenolic Acids

Phenolic compounds have diverse physiochemical characteristics which not only help in their biological functions but also play crucial role in their common applications.

Physical Properties of Phenolic Acids

The physical properties of phenolic acids are mentioned below:

Solid State: Phenolic acids are known to be present as solid compounds at room temperature and this crystallinity may be very low to very high depending on their chemical structure and purity.

Solubility: Water and organic solvent solubility in some phenolic acids may be variable, based on underlying chemical structure and associated functional groups. Polyphenolics can be broadly categorised into hydrophobic and hydrophilic based on the number of hydroxyl groups its name bears. These phenolic compounds with fewer hydroxyl groups are more soluble in non-polar solvents while those with more hydroxyl groups tend to be more soluble in polar solvents like water.

Color: The polyphenolic acids shows different colors, varying from colorless, yellow, brown, or red, due to some molecular structural features such as the substance, concentration, and pH levels.

Chemical Properties of Phenolic Acids

The chemical properties of phenolic acids are mentioned below:

Antioxidant Activity: Phenolic acids are known to donate hydrogen atoms or electrons in order to stop free radicals and thus prevent the consequences of oxidative process. This reduces free radical activity which in turn aids their ability to protect cells and tissues against oxidative damage, and ultimately contributes to their health benefits.

Reactivity: Phenolic acids can use different chemical routes that include oxidation, reduction, esterification, glycosylation or polymerization. These responses can influence their structure, availability, and the level of activity biologically, while also affecting their sensory properties noted, such as taste, fragrance and color.

pKa Values: Phenolic acids consist of one or more carboxylate ions, difference from them comes from their acidity. These anions may depend on pH conditions and form negatively charged carboxylate ions in water solutions. The phenolic acids are characterized by their acidity, which is typically assessed by pKa value that determines sensitiveness, involution potential, and reactivity as well as interactions with other molecules.

Chelating Ability: Chelation of modifiers metals is also one of the capabilities shown by phenolic acids. In this reaction coordination bonds are formed between metal ions and modifiers. They have significant bearing for their part in metallic ions homeostasis as well as for experimental use in metal chelation therapy and environmental cleansing.

Uses of Phenolic Acids

The modes of applications for both the phenolics and the phenolic acids are widely due to their beneficial properties. Some common uses include:

Antioxidants: Phenolic acids are popular natural antioxidants utilized in the food and beverage industry to minimize oxidative deterioration that affects taste and color causing early spoilage and shortest shelf life. They play a key role in preserving qualities and freshness of ingredients through blocking of lipid oxidation and the formation of undesirable taste.

Food Preservation: Polyphenols incorporated into food packaging improve the overall antimicrobial properties and it extend the freshness life of the foods that are perishable. They can inhibit the expansion of the microorganisms which are responsible for the spoilage of food and the passage of foodborne pathogens leading to improved food safety.

Nutraceuticals: These chemicals are added to supplements as well as in nutraceuticals because of their potential to improve or preserve health status. They are promoted as friendly and safe herbal medicine solutions to many health issues including but not limited to inflammation, heart diseases and oxidative stress caused ailments.

Cosmetics: Phenolic acids are being added to skincare and cosmetics products so to support the antioxidant feature which helps protect from oxidative stress and is connected with aging signs appearance. They can be utilized both for anti-inflammatory functions as well as to hydrate and maintain skin texture elasticity.

Pharmaceuticals: The study into therapeutic prospects of phenolic acids is primarily aimed at application in pharmaceuticals. They have a anti-inflammatory and antimicrobial activities that makes them perfect for research in drug development for a variety of health problems.

Agriculture: Polyphenolic compounds act as natural pesticides and herbicides: they are also employed to regulate plant growth. They are able to, different species of weeds, and, diseases of plants, and further help to the growth of plants.

Conclusion

In addition to promoting health and well-being, phenolic acids is are beneficial in food products manufacture and others such as cosmetics, medicine, and agriculture Antioxidants, antimicrobials, and anti-inflammatory attributes of these plants make them seek after worthy constituents for numerous health products meant to help. Nowadays, the studies are persistently advanced to get insights in the physics, bioactivity, and innovation uses of phenolic acids which delivers wide applications in the industry.

Also, Check

• Preparation of Phenols
• Chemical reactions of Alcohols, Phenols and Ethers
• Uses of Phenol

Frequently Asked Questions on Phenolic Acid

What are phenolic acids?

Phenolic acid is actually a group of compounds found in plants that possess a phenolic group and carboxyl group.

What types of foods have high in phenolic acids?

Sources of phenolic acids are food products which include berries, lemons, apples, grapes, spinach, kale, and onion in the category of fruits and vegetables; while nuts, seeds, whole grains, coffee, tea, and red wine are in the other category.

Are there any health benefits of phenolic acids?

Yes, there are health benefits of phenolic acid as polyphenolics’ components are known to provide with protection against the oxidative damage, anti-inflammatory properties and have been attributed to the reduced risk of developing chronic diseases, e.g. cardiovascular and cancer.

Are phenolic acids safe for consumption?

Phenolics are usually considered mild as long as they are consumed in moderate amounts in relation to the balanced diet. In spite of this, the overindulge of the intake of extracts with high level of polyphenols may cause adverse effects and thus are better taken in moderate amounts.

Can they be use for skin care products production?

Yes, phenolic acids are the botanical ingredients used in some skincare products and cosmetics because of their antioxidant properties, which act as a shield to the skin and slow down signs of aging. They may also have the ability to block free radicals, reduce exudation and swelling (inflammation) and promote well-being of the skin.