Plant Phytochemicals Compounds: Health Benefits

Phytochemicals, occurring naturally in plants, are bioactive nutrients found in fruits, vegetables, grains, and other plant-based foods. These compounds, responsible for the colors, fragrances, and flavors of plants, also contribute to protection against infections and predators by acting as antioxidants and neutralizing free radicals to prevent potential harm.

These naturally derived compounds are believed to make a substantial contribution to the health benefits associated with plant-based foods and beverages, surpassing the effects of vitamins and minerals. Examples of phytochemicals with potential health benefits include polyphenols, flavonoids, isoflavonoids, anthocyanidins, phytoestrogens, terpenoids, carotenoids, limonoids, phytosterols, glucosinolates, and fibers.

Phytochemicals are typically categorized into three groups:Polyphenols, further divided into flavonoids, 

*Phenolic acids, and other non-flavonoid polyphenols.
*Terpenoids, further subdivided into carotenoids and non-carotenoid terpenoids.
*Thiols, encompassing glucosinolates, allylic sulfides, and non-sulfur containing indoles.

Certain phytochemicals have been recognized for their potential health benefits, including inhibiting the formation of cancer-causing substances (carcinogens), preventing carcinogens from attacking cells, and aiding cells in halting and eliminating cancer-like changes.
Plant Phytochemicals Compounds: Health Benefits

Phenolic compounds

Phenolic compounds are secondary metabolites that are quite widespread in nature. Phenolics are widely distributed in plants, spices, vegetables, fruits, whole grains, green and black teas, coffee, fruit juices, olive oil, red and white wines and chocolates.

They play several physiological roles in plants were they occur, but many of them are also favorable to human health because of their antioxidant activity.

They are compounds that have one or more hydroxyl groups attached directly to an aromatic ring. Phenol is the structure upon which the entire group is based.

Phenolics can exhibit simple structures such as arbutin or complex ones such as those characteristics of the tannin class.

Ribereau-Gayon in 1972 grouped the phenols into three families as follows:
*Widely distributed phenols – ubiquitous to all plants, or of importance in a specific plant
*Phenols that are less widely distributed – limited number of compounds known
*Phenolic constituents present as polymers

Phenolics compounds have been reported to have multiple biological effects, including antioxidant activity, to prevent heart disease, reduce inflammation, lower the incidence of cancers and diabetes, as well as to reduce rates of mutagenesis in human cells.
Phenolic compounds

Phenolic compound in olive oils

Phenolic compounds are often described as effective antioxidants. These compounds have a great importance for several characteristics of the olive oil, such as flavor, shelf-life and resistance against oxidation.

The class of phenols present in olive oils encompasses a large number of different substances such as vanillic acid, caffeic acid, hydroxytyrosol, tyrosol, oleuropein, ligstroside, gallic acid, coumaric acid and flavonoids. In olive oils the bitter taste is due to phenolic compounds and cinnamic acid, while the pungency is due to oleuropein.

The amount of phenolic compounds in olive oils cultivars varies from 150 to 700 ppm and is affected by various factors such as cultivar, degree of maturation, climatic conditions and pest damage to fruit. Green olives oil in phenolic content and with a more aromatic and fruity flavor.

Oleuropein is the major phenolic in olive fruits. Oleuropein underwent significant changes in its concentration during fruit development.

Oleuropein has been shown to be responsible for the high resistance, robustness and good immune function of the olive tree. In it original, unaltered form, this substance lowers, blood pressure, dilates blood vessels, and protects against heart rhythm disturbances.
Phenolic compound in olive oils

Coffee constituents of chlorogenic acid

The chlorogenic acids are ubiquitous in the plant kingdom. Although chlorogenic acids are common in vegetables foodstuffs, the relatively large quantity present in coffee make it an important dietary sources.

Chlorogenic acid and its isomers represent major coffee constituents of phenolic acid. They are family esters of quinic acid with several hydroxycinnamic acids, particularly caffeic, ferulic, p-coumaric acids.

In coffee they are essentially mono- and diesters and by far the prevailing acids. Other esters may occur but generally only in small amounts.

The quality of coffee depends in part on the relative proportion of mono and dichlorogenic acids, The ratio between these two acids is slightly less in robusta than in arabica. An excess of dichlorogenic acids might result in a metallic after-taste in the beverage.

Oral ingestion by man of 200 mg of chlorogenic acid was found to stimulate stomach secretion with enhancement of hydrochloric acid production. Caffeic acid had the same effect, and quinic acid, XII was inactive.
Coffee constituents of chlorogenic acid

Rice flavor compounds

There are many distinct yet subtle flavors and textures that influence rice eating quality. In addition to aroma, flavor is another factor contributing to consumer acceptance and repeat purchase of rice. Rice consumers are aware of these flavors and often demand what they perceived to be the best quality rice.

There are many chemicals that contribute to the aroma and flavor of rice. 1-butanal, 1-hexanal, 1-heptanal, methyl ethyl ketone, 1-pentanal and propanal are responsible for what is known as the ‘old’ or ‘stale’ aroma of stored rice, while 1-butanal and 1-heptanan are involved in the aroma of ‘refresh’ rice.

The stale flavors associated with old rice that had been stored at warm temperatures for some time before cooking has been attributed to the formation of free fatty acids by lipase activity and to lipid oxidation, not to these aroma compounds.

The lipid oxidation products, pentanal, and hexanal, have been implicated in stale rice flavor. These aldehydes can be formed by lipoxygenase activity on linoleic and linolenic acids.

There is no single compound found in cooked rice that can described as ‘cooked rice’ and the aroma probably arises from a mixture of several compounds. The majority of compounds in the headspace cooked rice are lipid oxidation products.
Rice flavor compounds

Food flavoring: Vanilla

Vanilla is one of the world’s most important flavoring materials. It is the fruit of an orchid. Scientific name for vanilla orchid: Vanilla planifolia Jacks. Family name: Orchidaceae.

Vanilla isolated from the bean of the vanilla orchid is a complex mixture of many compounds some of which are synergistically most responsible for vanilla’s organoleptic value.

Cured vanilla beans contain vanilla secondary aromatic compounds, small amounts of heliotropin, volatile oil, resins, tannin, wax, cellulose and water.

Although vanilla extract contains more than 300 compounds, the most studied and commonly associated with vanilla extract quality are vanillin, vanillic acid, p-hydroxybenzaldehyde and p-hydroxybenzoic acid.

However, their value is not determined by the vanillin content but more by their fragrance.

Vanilla extract has been sold commercially in the United States for over a century. Many companies have been producing vanilla extract since the introduction of vanilla to the United States.

It is the most popular flavor in the baking and chocolate industries in North America. Vanilla is also used as a flavoring of beverages, ice cream, confections, cakes, custards, yoghurt, compotes, puddings and candy.
Food flavoring: Vanilla

Flavor compounds of Allium

Allium is a large and diverse genus of about 500 species. Unlike other crop species, the Alliums, which include onion, garlic, leek, shallot, chives, rely on sulfur for their unique flavor. The major flavor of Alliums results from the activity of the enzyme, alliinase, acting on certain sulfur-containing compounds when tissues are broken or crushed.

Sulfur is the primary element in many compounds that produce a specific flavor profile to a specific species of Allium.

The volatile flavor compounds in onions are mainly propyl disulfide and methyl propyl disulfide. Allicine and its analogue are not stable in air. They gradually decompose to produce disulfide or trisulfide compounds, which are the major flavor compounds found in Allium plants.

Each spice belonging to an Allium plant can be characterized by the kind of major sulfide compound contained in it. Sulfur and carbonyl compounds are two major categories of the volatiles observed in Allium plants.

There are three main R-group to be considered for the flavor compounds of Allium plant:
*Methyl group (CH3-)
*Propyl group (CH3CH2CH2-)
*Allyl group (CH2=CH.CH2-)

Compounds with a propenyl group (CH3CH=CH-) are also found in onion. Differences in smell or flavor among garlic, onion, leek, and others are due to the ratio of these groups.
Flavor compounds of Allium

Anthoxanthins in food

Anthoxanthin pigment is a flavonoid and is similar to anthocyanin, but it exists in less oxidized state as the oxygen on the central group is uncharged.

It is actually a composite of compounds known as flavones, flavonols, and flavonones. The anthoxanthins are glycosides when on boiling with dilute acid yield one or two molecules of monosaccharides and a flavone or flavone derivatives.

Anthoxanthins are white or pale yellowish, water-soluble pigments found in a plant’s cell sap. They contribute the cream or white color of cauliflower, onions, white potatoes and turnips.

turnips

Short cooking is desired. With prolonged heat, the pigment turns into a brownish gray color. For example, white, anthocyanin potatoes with their low organic acid content may become dark colored after prolonged cooking due to formation of an iron-chlorogenic acid complex.

Vegetable containing anthoxanthins, such as turnips and cauliflower can also change color if they are cooked in a covered pan for long periods of time.

The sulfur containing compounds in the vegetables will be released in the form of hydrogen sulfide which will convert the colorless anthoxanthin to anthocyanins as will be noted in the pink pigment in overcooked turnips and cauliflower.
Anthoxanthins in food

What is anthocyanidin?

When the sugar moiety of an anthocyanin is hydrolyzed, the aglycone (non-sugar hydrolysis product) is referred to as an anthocyanidin.

The color of anthocyanins and anthocyanidins results from excitation of molecule by visible light. At pH values lower than 3, the anthocyanidin appears as the red flavylium cation, and at pH values higher than 6 it is preset as the blue quinonoidal base form.

The richest sources of anthocyanidins to the diet are red wine and fruit, particularly berries. Foods can have one or a variety of anthocyanidins and the concentration is influenced by environmental conditions, ripeness, cultivar, cultivation site, processing and storage.

Only three types of anthocyanidins have been identified in plant tissues. Pelargonidin, cyanidin and delphinidin are wide spread in nature with cyanidin the most common.

Cyanidin is the anthocyanidin found in red cabbage, pelargonidin occurs in radishes and red-seeded varieties of bean and delphinidin occurs in aubergines.

Anthocyanidins are less water soluble than their corresponding glycosides (anthocyanins) and they are not found free in nature.

Freezing may be the best method of preserving anthocyanidins in foods so as the consumption can continue throughout the year even when particular foods such as berries are not in season.
What is anthocyanidin?

Phytosterols in foods

Phytosterols are present in all plants and in foods containing plant-based raw materials. Phytosterols also known as plant sterols and stanols are in many everyday foods.

Chemically, phytosterols are triterpenes, composed of a steroid skeleton and alkyl side chain. They are closely related to cholesterol, but there also structurally distinct with the presence of a side chain substitution of methyl or an ethyl group carbon 24.

In normal diets vegetable oils and products based on them are generally acknowledged to be richest sources of phytosterols.

Beta- sitosterol

Vegetables oils such as corn, sunflower, soybean and rapeseed oils which containing between 0.1% and 0.5% are the main sources of plant sterols in typical Western diets.

Legumes (up to 0.2%) and some seeds (e.g. sunflower and sesame around 0.6%) are also good sources while other vegetables and fruits contain slightly lower amounts of plant sterols.

One of the biggest advantages of phytosterols is that they block LDL without disrupting HDL.

The three primary phytosterols are Beta-Sitosterol, Campesterol, and Stigmasterol. These three main phytosterols occur naturally in varying rations in foods that contain phytosterols.

Minor phytosterols are avenasterol, oryzanol, fucosterol and ergosterol. Sitosterol, Campesterol, and Stigmasterol are predominant in sterol fractions of the soy and corn oils.
Phytosterols in foods

What is proanthocyanidins?

Proanthocyanidins also called condensed tannins, are oligomers, and polymers of monomeric flavonoids. It represents a major group of phenolic compounds that occurs ubiquitously in woody and some herbaceous plants.

More specifically, they are polyflavans, condensed molecules of those flavonoids with a saturated ‘C’ ring. Linkage of the flavan-3-ol units occurs mainly through the C4  C8 bond, although a C4  C6 bond may also exits (B-type linkages).

Proanthocyanidins are considered secondary metabolites of plants, i.e. they are not required for the structural or metabolic integrity of the organism. The proanthocyanidins are classified according to the type of flavan-3-ols present, which vary in their OH patterns at C3 on the B ring.

The two major classes of proanthocyanidins found in berry fruit include procyanidins, composed exclusively of epi (catechin) units, and propelargonidins, composed exclusively of (epi)afzelechin units.

When tannins are consumed by man, they often have astringent properties. This properties cause by the cross-linkage of protein and glycoproteins and a corresponding loss of lubrication in the mouth and throat.

Proanthocyanidins are common in fruits, fruit pods, sees and shell, either as preracetates or in free phenolic forms.
What is proanthocyanidins?

Classification of lipids: Compound lipids

Compound lipids differ from simple lipids in having an additional nonlipid portion.

Compound lipids usually consist of fatty acid, an alcohol and one or more other groups such as phosphorus or nitrogen. These can be formed in the brain and central nervous system.

Compound lipids are not fats, and their amount remains constant in the organisms.

The compound lipids are amphipathic molecules. They can be subclassified into the following categories.
*Phospholipids: contain an additional phosphate group
*Glycolipids: contain carbohydrate groups. This lipid is present in combination with a carbohydrate (galactose).

Lecithin, the best known among phospholipids in plant cells, is an essential structural material for living cell membrane, whether to maintain continuity between the water and lipid phases inside and outside the cells. 

The functions of certain enzymes depend upon their attachments to lipids such as lecithin.
Classification of lipids: Compound lipids

What is quercetin?

Several hundred flavones and flavonol aglycones are known, but only three are common: kaempferol, quercetin, and myricetin.

Quercetin has the widest distribution in nature of phenolic compounds, and 135 different glycosides of quercetin.

It is the potent flavonoid and antioxidant found naturally in the pulp of many citrus fruits and in apple skins, buckwheat, red onions, red grapes, wine, and tea. Quercetin also found in onions, cayenne pepper, and garlic.

It is estimated that the average adult diet provides up to 50 mg of quercetin each day.

Evidence indicates that quercetin has antiviral activity, both in vivo and in vitro, most markedly against herpes simplex type I, para-influenza types 3, polio virus type I, and respiratory syncytial virus.

In cardiovascular system, it prevents free radicals from oxidizing low-density lipoproteins (LDL). If LDL becomes oxidized, it will be precursor to arterial damage and atherosclerosis.

However, hypersensitive individuals may experience headaches or tingling. While rare, other reported side effects include gastrointestinal discomfort, hematoma, and kidney toxicity.
What is quercetin?

Polyphenols in tea

Tea is the most widely consumed beverage in the world after water. The daily consumption is around 3 billion cups per day.

Regular intake of tea is associated with improved antioxidant status in vivo, which may contribute to lowering the risk of coronary heart disease, stroke, and certain type of cancers.

The polyphenols in tea mainly include the following six groups of compounds: flavonols, hydroxy-4-flavonols, anthocyanins, flavones, flavonols, and phenolic acids.

Among these, the flavonols mainly catechins are most important and occupy 60-80% of the total amount of polyphenols in tea.

The tea plant is known to contain seven kinds of major catechins and traces of various other catechin derivatives.

These catechins are present in all part of the tea plant; 15-30% are present in the tea shoots, and there is also a high content in the second and third leaves.

About 90-95% of the flavonols undergo enzymatic oxidation to products which are closely responsible for the characteristics color of tea infusion and its taste.

During the manufacturing of tea, the content of polyphenols increases slightly at the beginning of withering but decreases right after.

Although the trend for the changes of polyphenols appears similar in different varieties the absolute content of polyphenols are different among them.
Polyphenols in tea