UMALI, KIRBY KEGS J.WEEK 12- TERPENES AND LIPIDS

TERPENES

Plant terpenoids are used extensively for their aromatic qualities. The chief constituents of essential oils It is colorless and fragrant liquid, lighter than water and evaporates with steam. Soluble in

organic solvents and few in water. Camphor is an exemption because it is a solid They are open chain or cyclic unsaturated compounds having one or more double bonds.

Some with antiseptic activity undergo polymerization and dehydrogenation undergo oxidation by most oxidizing agents They play a role in traditional herbal remedies and are under investigation for

antibacterial, antineoplastics, and other pharmaceutical functions. Plants do not only accumulate terpenes for herbivore defense, but also emit volatile

blends in response to herbivory and many other biotic and abiotic stresses. These terpene containing volatiles attract natural enemies of the attacking herbivores but

due to the complexity of these volatile blends, it is difficult to attribute a specific function to a particular terpene

Terpenoids are volatile substances which give plants and flowers their fragrance. They occur widely in the leaves and fruits of higher plants, conifers, citrus and eucalyptus ‘terpene’ was given to the compounds isolated from terpentine, a volatile liquid isolated

from pine trees terpene’ was originally employed to describe a mixture of isomeric hydrocarbons of the

molecular formula C10H16 occurring in the essential oils obtained from sap and tissue of plants, and trees.

general term ‘terpenoids’ which include hydrocarbons and their oxygenated derivatives Terpenoids are the hydrocarbons of plant origin of the general formula (C5H8)n as well

as their oxygenated, hydrogenated and dehydrogenated derivatives ISOPRENE is the basic unit of terpenes. Isoprene units are joined in the terpenoid via

‘head to tail’ fashion- Isopentyl diphosphate (IPP) and dimethyl allyl diphosphate (DMAPP) to be the actual building blocks

But this rule is not fixed, it just a guideline, some are connected via tail to tail fashion like those of the carotenoids.

Alkyl group destabilizes the terpenoids They can be classified on the basis of value of n or number of carbon atoms present in the

structure.o Acyclic Terpenoids: They contain open structure.o Monocyclic Terpenoids: They contain one ring in the structure.o Bicyclic Terpenoids: They contain two rings in the structure.o Tricyclic Terpenoids: They contain three rings in the structure.o Tetracyclic Terpenoids: They contain four rings in the structure

Biosynthesis of terpeneso All terpenes are formed by the reaction between IPP and DMAPPo There are 2 biosynthetic pathways for the production of IPP and DMAPP, the

mevalonate pathway and the more recently discovered deoxyxylulose pathwayo Two known pathway: (1) IPP is continuously added to DMAPP in a heat to tail

manner via phenyltransferases that serves as catalyst (2) thru consecutive condensation of IPP with an allylic diphospate.

o Variation in isoprene repetition, cyclization , and rear arrangement is responsible for terpene structural diversity

Terpenes as pharmaceutical agent are use as antibiotics, antioxidants, anticancer and anti-

inflammatory

TYPES OF TERPENES

Monoterpenes Are essential constituents of volatile oils, scents, and defensive resins of aromatic plants Nonnutritive components of plants especially the citrus family Has antitumor activity and can help in regression of malignants Limonene is the most abundant monocyclic monoterpene in nature and the major

constituents of peel oil found in citrus plants namely oranges, lemon and calamansi

Limonene has an establish chemotherapeutic activity Carvone can prevent chemically induced stomach and lung cancer

Perillyl alcohol an analog of limonene exhibit chemotherapeutic activity against liver cancer

Antitumor activity of monoterpenes acts by apoptosis and interference in key regulatory proteins

Pyrethrin and permethrin (analog of the former) are pediculicides or treatment for lice

Sesquiterpenes Less volatile than monoterpenes Sesquiterpene lactones are responsible for its anti inflammatory activity and other

medicinal functions Artemisinin is an example of the compound with antimalarial activity Some have antituberculosis activity

Diterpenes

The most important compound for this class the phytol- used as a biomarker and a sidechain of chlorophyll

Paclitaxel is one of the most important classes of diterpenes used as anticancer agents by inhibiting microtubule polymerization

Sesterterpenes least common type of terpenes and commonly found in fungi and microorganisms

Tetraterpenes The basic example is carotenoids- These are lipid soluble pigments widely distributed

in all plants including bacteria. Carotenoids are present either in simple unsaturated hydrocarbon form or their oxygenated derivatives known as xanthophylls

Hydrocarbons: e.g. Carotenes and Lycopene Xanthophylls: e.g. Zeaxanthin, Capsanthin, Violaxanthin, Fucoxanthin, Lutein etc.

LIPIDS

Are classes of biological molecules that are insoluble in water and soluble in nonpolar solvents. There are many different categories of lipids and each category has different components present in its structure.

These are a large and diverse group of naturally occurring organic compounds, esters of fatty acids and alcohols and polyols. These are soluble in nonpolar organic solvents (e.g. ether, chloroform, acetone & benzene) and generally insoluble in water.

Basic structure or backbone upon hydrolysis is fatty acid

These can be classified as: 1. Simple lipids (esters of fatty acids with alcohols) e.g. triglycerides like fats and oils, waxes.

2. Compound lipids They contain (in addition to fatty acids and alcohols) additional groups as phosphate (e.g. phospholipids), carbohydrates (e.g. glycolipids) and proteins (e.g. lipoproteins).

Biological functions of lipids: They provide energy storage and metabolic fuels. Cholesterol is a precursor of steroid hormones, bile acids (which help in digestion of

dietary fats) and vitamin D.

They act as functional and structural components of the cell membrane. Lipoproteins (e.g. LDL & HDL) are a mean for transporting lipids in blood. Imbalance in lipid metabolism can lead to major clinical problems such as obesity

and atherosclerosis.

They show great structural variety and can be studied in following sections: a. Fatty Acids b. Fats and Oils c. Waxes d. Soaps and Detergents e. Phospholipids

Fatty acids are present in fats and oils as glycerides or esters of glycerol except in sperm oil, where

some of the fatty acids are esterified with fatty alcohols, mainly cetyl alcohol. The fatty acids are released by hydrolyzing ester linkage. This is done by chemically

adding water, a process commonly referred to as fat splitting. The natural fatty acids are generally aliphatic compounds with a carboxyl group at the

end of a straight carbon chain. Nearly all of them have an even number of carbon atoms. The acids differ from one another in the number of carbon atoms and the number and

position of the double or unsaturated bonds. Two types: saturated fatty acid and unsaturated fatty acid SATURATED FATTY ACID

o The saturated acids contain no double bonds. They vary in chain length from butyric, which contains four carbon atoms, to lignoceric, which has 24C

o At room temperature the shorter chain length acids are liquid. Lauric and all longer chain acids are solids at room temperature.

o The most widely distributed and the most commercially important are palmitic and stearic acids. NO DOUBLE BOND or C=C etc.

o Commercial stearic acid in its different grades consists of roughly equal parts of these two acids

o E.g. Common cooking oil

UNSATURATED FATTY ACID

o The unsaturated acids differ from one another in the number of carbon atoms, the number of double bonds, the position of the double bonds, and the geometry of the double bonds.

o All of the unsaturated acids, with the exception of elaidic, are liquid at room temperature

o Also called essential fatty acids since the body cannot produce these compounds by the human body and must acquire it thru our diet and these are linoleic and linolenic acid

o contain one or more cis double bonds- The presence of cis double bonds has an important effect on the melting point of the fatty acid. Cis double bonds form rigid kinks in the fatty acid chains (remember that there is no rotation around a double bond), and the result is that unsaturated fatty acids cannot line up very well to give a regularly arranged crystal structure.

SIMPLE LIPIDS

Waxes Waxes are esters of fatty acids with long chain monohydric alcohols and may also

contain hydrocarbons. These are widely distributed in nature like leaves and fruits of many plants have waxy coatings, which protect them from dehydration.

Most of the waxes are mixtures of esters.E.g. of some common waxes are: Spermaceti wax- CH3(CH2)14COO-(CH2)15CH3,

Beeswax-CH3(CH2)24COO-(CH2)29CH3 and

Carnuaba wax- CH3(CH2)30CO2-(CH2)33CH

Fats and Oils

These are phospholipids of fatty acids with glycerol commonly known as triglycerides, found in both plants and animals, and compose one of the major food groups of our diet.

Triglycerides that are solid or semisolid at room temperature are classified as fats, and found predominantly in animals.

The liquid triglycerides are called as oils and originate mainly from plants; triglycerides obtained from fish are also oils.

Triglycerides are triesters of glycerol and three fatty acid molecules. The fatty acids in the triglyceride can be the same or different.

Naturally occurring fats and oils are typically mixtures of different triglycerides.- the R group or fatty acid attached to it may be of single type or multiple kind

Triglycerides are much better adapted than glycogen to serve as storage form of energy. They are not only stored in large amounts but also yield over twice as much energy as

carbohydrates. Since fats tend to remain in the stomach longer than carbohydrates and are digested more slowly, they also have greater satiety value than carbohydrates

COMPOUND LIPIDS

Phospholipids These are main constituents of cell membranes; resemble the triglycerides in being ester

or amide derivatives of glycerol or sphingosine with fatty acids and phosphoric acid. The phosphate moiety of the resulting phosphatidic acid is further esterified with

ethanolamine, choline or serine in the phospholipids itself. The fatty acid components may be saturated or unsaturated.

also called phosphatids They serve primarily as structural components of membranes and are never stored in

large quantities. As their name implies, phospholipids contain phosphorus in the form of phosphoric acid

groups. They differ from triglycerides in possessing usually one hydrophilic polar “head” group

and usually two hydrophobic nonpolar “tails”. For this reason, they are often called polar lipids. Thus, phospholipids are amphipathic

In phospholipids, two of the OH groups in glycerol are linked to fatty acids while the third OH group is linked to phosphoric acid.

The phosphate is further linked to one of a variety of small polar head groups (alcohols). Folch and Sperry (1955) have classified phospholipids into phosphoglycerides, phosphoinositides and phosphosphingosides

A. Phosphoglycerides

These are the major phospholipids found in membranes and contain two fatty acid molecules or “tails” esterified to the first and second hydroxyl groups of glycerol. The third hydroxyl group of glycerol forms an ester linkage with phosphoric acid.

phosphoglycerides contain a second alcohol, which is also esterified to the phosporic acid. This is referred to as ‘head alcohol group’ as it is present at one end (‘head’) of the long phosphoglyceride molecule.

phosphoglycerides differ in their head alcohol groups All of them contain two nonpolar tails, each consisting of a long chain (usually C16 or

C18) fatty acid. Usually one of the fatty acids is saturated and the other unsaturated; the latter is always esterified to the middle or Beta-hydroxy group of glycerol.

A noteworthy feature of the phosphoglycerides is that they contain an asymmetric carbon atom at position 2 in the glycerol part of their molecule. It has the L-configuration since it is related to L-glyceraldehyde. All phosphoglycerides have a negative charge on phosphoric group at pH 7.

Lecithins – also called PHOSPHATIDYL CHOLINEo The lecithins are required for the normal transport and utilization of as

other lipids esp., in the liver of animals. In their absence, accumulation of lipids occurs in the liver to as much as 30% against a normal value of 3-4%, giving rise to a condition called “fatty liver”.

Cephalins -The cephalins (kephalusG = head) are closely associated with lecithins in animal tissues.

o These have also been identified from soybean oil. o These are similar in structure to the lecithins except that the choline is

replaced by either ethanolamine or serine. Serine is the biochemical precursor of ethanolamine.

o Two types of cephalins are recognized, phosphatidyl ethanolamine and phosphatidyl serine. Like lecithins, the cephalins it also exist in 2 forms,

and b, depending upon the relative positions of the two substituent fatty acids.

Plasmalogens (Phosphoglyceracetals)- constitute about 10% of the phospholipids of the brain and muscle.

o These are apparently not found in significant quantities in plant tissues.

o Structurally, these resemble lecithins and cephalins but have one of the fatty acids replaced by an unsaturated ether.

o Since the nitrogen base can be choline, ethanolamine or serine,three types of plasmalogens are accordingly distinguished : phosphatidal choline, phosphatidal ethanolamine and phosphatidal serine.

B. Phosphoinositides (Phosphatidyl inositols) Found to occur in phospholipids of brain tissue and of soybeans and are of considerable

importance because of their role in transport processes in cells. These are phospholipids where a cyclic hexahydroxy alcohol called inositol replaces base are also classified as glycolipids, in as much as they contain carbohydrate residue.

C. Phosphosphingosides (Sphingomyelins) These compounds are commonly found in nerve tissue esp., in the myelin sheath of the

nerve (hence their name, sphingomyelins) and apparently lack in plants and the microorganism

These differ from other phospholipids in their lack of glycerol and the presence of another nitrogenous base sphingosine or a closely related dihydrosphingosine, besides choline, in place of glycerol.

Sphingomyelins are electrically charged molecules and contain phosphocholine as their polar head groups.

DERIVED LIPIDS

Steroids are one of the most studied classes of biological compounds and are often found in

association with fat. Since they contain no fatty acids, they are nonsaponifiable. All steroids may be considered as derivatives of a fused and fully saturated ring system

called cyclopentanoperhydrophenanthrene or sterane. This system consists of 3 cyclohexane

rings (A, B and C) fused in nonlinear or phenanthrene manner and a terminal cyclopentane ring (D).

be emphasized that in steroids the hexagonal rings are not the benzene rings as in them

the valences of C atoms are fully satisfied by hydrogen bonds, unless shown otherwise. All naturally occurring steroids are in chair configuration Steroids containing hydroxyl groups (hydroxy steroids) are often referred to as sterols.

Broadly speaking, the various sterols fall under 2 groups based on their source : the animal sterols or zoosterols (cholesterol, cholestanol, coprostanol) and the plant sterols or phytosterols (ergosterol, stigmasterol, spinastero

Includes cholesterol, bile acids and hormone and vitamins

Cholesterol It is not only an important component of some cell membranes and of plasma lipoproteins

but also the precursor of many other biologically important steroids, such as bile acids and various steroid hormones. It is the principal sterol of higher animals and is especially abundant in nerve tissues and in gallstones. In occurs either free or as fatty esters in all animal cells

has a molecular formula, C27H45OH. In addition to an OH group at C3, there is a double bond at C5. The hydroxyl group constitutes its polar head, the rest of the molecule is hydrophobic

It is a white crystalline solid and is optically active Saturated fats of animals origin (such as butter, ghee and lard) do contain cholesterol but

vanaspati, which is derived from vegetable oils, does not contain cholesterol. Only a little portion of the body cholesterol is derived from diet. The bulk of it is synthesized in the body. Unsaturated fatty acids lower blood cholesterol levels by controlling cholesterol’s synthesis as well as its elimination from the body.

Bile acids

The bile acids are the important end products of cholesterol metabolism in higher plants. About 20 natural bile acids have been characterized

these are derived from a C 24 parent steroid, cholanic acid and resemble coprostanol in having rings A and B in cis form

Various bile acids differ from each other in the number and position of OH groups which are all in a configuration. In the bile acids, the number of OH group(s) may be 1, 2, or 3 and the position of OH group(s) may be any of the following: 3, 6, 7, 11, 12 and 23.

The side chain is usually made up of 5 carbon atoms and bears the carboxyl group