Brief discussion about brain

The brain is one of the most complex and magnificent organs in the human body. Our brain gives us awareness of ourselves and of our environment, processing a constant stream of sensory data. It controls our muscle movements, the secretions of our glands, and even our breathing and internal temperature. Every creative thought, feeling, and plan is developed by our brain. The brain’s neurons record the memory of every event in our lives.

Anatomy of the Brain

There are different ways of dividing the brain anatomically into regions. The most common method and divide the brain into three main regions based on embryonic development: the forebrain, midbrain and hindbrain. Under these divisions:

• The forebrain (or prosencephalon) is made up of our incredible cerebrum, thalamus, hypothalamus and pineal gland among other features. Neuroanatomists call the cerebral area the telencephalon and use the term diencephalon (or interbrain) to refer to the area where our thalamus, hypothalamus and pineal gland reside.
• The midbrain (or mesencephalon), located near the very center of the brain between the interbrain and the hindbrain, is composed of a portion of the brainstem.
• The hindbrain (or rhombencephalon) consists of the remaining brainstem as well as our cerebellum and pons. Neuroanatomists have a word to describe the brainstem sub-region of our hindbrain, calling it the myelencephalon, while they use the word metencephalon in reference to our cerebellum and pons collectively.

Before exploring these different regions of the brain, first let’s define the important types of cells and tissues that are the building blocks of them all (Singh, 2006).

Histology

Brain cells can be broken into two groups: neurons and neuroglia. Neurons, or nerve cells, are the cells that perform all of the communication and processing within the brain. Sensory neurons entering the brain from the peripheral nervous system deliver information about the condition of the body and its surroundings. Most of the neurons in the brain’s gray matter are interneurons, which are responsible for integrating and processing information delivered to the brain by sensory neurons. Interneurons send signals to motor neurons, which carry signals to muscles and glands.

Neuroglia, or glial cells, act as the helper cells of the brain; they support and protect the neurons. In the brain there are four types of glial cells: astrocytes, oligodendrocytes, microglia, and ependymal cells.

• Astrocytes protect neurons by filtering nutrients out of the blood and preventing chemicals and pathogens from leaving the capillaries of the brain.
• Oligodendrocytes wrap the axons of neurons in the brain to produce the insulation known as myelin. Myelinated axons transmit nerve signals much faster than unmyelinated axons, so oligodendrocytes accelerate the communication speed of the brain.
• Microglia act much like white blood cells by attacking and destroying pathogens that invade the brain.
• Ependymal cells line the capillaries of the choroid plexuses and filter blood plasma to produce cerebrospinal fluid.

The tissue of the brain can be broken down into two major classes: gray matter and white matter.

• Gray matter is made of mostly unmyelinated neurons, most of which are interneurons. The gray matter regions are the areas of nerve connections and processing.
• White matter is made of mostly myelinated neurons that connect the regions of gray matter to each other and to the rest of the body. Myelinated neurons transmit nerve signals much faster than unmyelinated axons do. The white matter acts as the information highway of the brain to speed the connections between distant parts of the brain and body.

Other important parts of the brain

Cerebrospinal fluid (CSF)

The cerebrospinal fluid (CSF) is a clear, watery liquid that surrounds cushions and protects the brain and spinal cord. The CSF also carries nutrients from the blood to, and removes waste products from, the brain. It circulates through chambers called ventricles and over the surface of the brain and spinal cord. The brain controls the level of CSF in the body.

Meninges

The brain and spinal cord are covered and protected by 3 thin layers of tissue (membranes) called the meninges:

• dura mater – thickest outer layer
• arachnoid layer – middle, thin membrane
• pia mater – inner, thin membrane

CSF flows in the space between the arachnoid layer and the pia mater. This space is called the subarachnoid space.

The tentorium is a flap made of a fold in the meninges. It separates the cerebrum from the cerebellum.

• The supratentorial area of the brain is the area above the tentorium. It contains the cerebrum, the first and second (lateral) ventricles, the third ventricle, and glands and structures in the centre of the brain.
• The infratentorial area is located at the back of the brain below the tentorium. It contains the cerebellum and brain stem. This area is also called the posterior fossa.

Corpus callosum

The corpus callosum is a bundle of nerve fibres between the 2 cerebral hemispheres. It connects and allows communication between both hemispheres.

Thalamus

The thalamus is a structure in the middle of the brain that has 2 lobes or sections. It acts as a relay station for almost all information that comes and goes between the brain and the rest of the nervous system in the body.

Hypothalamus

The hypothalamus is a small structure in the middle of the brain below the thalamus. It plays a part in controlling body temperature, hormone secretion, blood pressure, emotions, appetite, and sleep patterns.

Pituitary gland

The pituitary gland is a small, pea-sized organ in the centre of the brain. It is attached to the hypothalamus and makes a number of different hormones that affect other glands of the body’s endocrine system. It receives messages from the hypothalamus and releases hormones that control the thyroid and adrenal gland, as well as growth and physical and sexual development.

Ventricles

The ventricles are fluid-filled spaces (cavities) within the brain. There are 4 ventricles:

• The first and second ventricles are in the cerebral hemispheres. They are called lateral ventricles.
• The third ventricle is in the centre of the brain, surrounded by the thalamus and hypothalamus.
• The fourth ventricle is at the back of the brain between the brain stem and the cerebellum.

The ventricles are connected to each other by a series of tubes. The fluid in the ventricles is cerebrospinal fluid (CSF). The CSF flows through the ventricles, around the brain in the space between the layers of the meninges (subarachnoid space) and down the spinal cord.

Pineal gland

The pineal gland is a very small gland in the third ventricle of the brain. It produces the hormone melatonin, which influences sleeping and waking patterns and sexual development.

Choroid plexus

The choroid plexus is a small organ in the ventricles that makes CSF.

Cranial nerves

There are 12 pairs of cranial nerves that perform specific functions in the head and neck area. The first pair starts in the cerebrum, while the other 11 pairs start in the brain stem. Cranial nerves are indicated by number (Roman numeral) or name (Chatterjee, 1977).

The Physiology of the Blood-Brain Barrier

The BBB is not one single structure or membrane in the brain, but it is created by the way the blood vessels in the brain are organized. Thus, understanding the BBB requires an understanding of the anatomy and physiology of the blood vessels in the brain. Both large and small capillaries form a richly branched and complex network throughout the entire brain tissue. Like a chimney made of individual bricks, the brain blood vessels consist of a monolayer of endothelial cells that are connected with each other by tight junctions (zonulae occludentes) (Crone and Olsen, 1982). The part of the cell's membrane facing the bloodstream is called the "luminal" membrane (Dehouck, 1990; Arthur, 1987; Tao-Cheng, 1987), and the side which is exposed to the actual brain tissue is called the "abluminal" membrane. This part faces the extracellular liquid of the brain parenchyma where pericytes and end feet of astrocytes surround the blood vessels. The most important site of the BBB lies at the cerebral microvessels, that is, the very fine vessels that have extremely small diameters. Because endothelial cells are very polarized, that is, essentially similar to the epithelium, they exhibit very low pinorytic activity and possess a high number of mitochondria that are needed for the multiple energy-dependenat ctive transport mechanisms found in endothelial cells (Stevard and Wiley, 1981). Peripheral vessels in the rest of the body can much more easily transport molecules across their membrane because they are fenestrated and have many active transcellular transport mechanisms. In contrast, in central blood vessels of the brain, even small molecules like antibiotics have great difficulty crossing the barrier and only a limited number of molecules can actively cross the endothelial cells. Here, the endothelial cells use specific transport systems to allow the influx of glucose, iron, amino acids, peptides, small organic acids, and others. This is necessary so that substances which are critical for brain metabolism and function can gain fast and efficient access to the brain via specific energy-dependent carrier mechanisms at the endothelium (D'Amore, 1990).

The Role of Pericytes

Perirytes, which are located on the abluminal side of the endothelial cells, are also part of the BBB. Pericytes are a physiological heterogeneousc ell population and are found on all micro vessels in nearly every organ (D'Amore, 1990), but they never cover the entire blood vessel. The pericytes, which are located on the "brain side," are encapsulated by the basal membrane of the endothelial cells, and they are responsible for the synthesis and release of different components of the basal membrane and the extracellular matrix such as collagen and glycosaminoglycocan (Stramm et al., 1987). The basal membrane of the endothelial cells and that of the pericytes are closely attached to each other so that both cells have a common basal membrane (Shepro and Morel, 1993). Electron microscopy studies have revealed fenestrations between pericytes and endothelial cells (Frank et al., 1980), and perirytes have contractile properties that may play a role in the regulation of the blood flow. Several molecules are involved in these contractile functions such as actin, myosin, tropomyosin, vimentin, and desmin (Frey et al., 1991; Risau et al., 1992). Pericytes have an important role in the function of the BBB. They are responsible for the maintenance of the barrier function and the stability of the vessel (Kimelberg and Norenberg, 1989).

The Role of Astrocytes

Astrocytes (which are brain glia cells) also contribute to the BBB, and they are attached with their endfeet to the pericytes and the endothelial cells. Astrocytes are glial cells responsible for the homeostasis and the ion regulation in the brain (Kimelberg and Norenberg, 1989), but their end feet cover the blood vessels only partially. In contrast to endothelial cells and pericytes, astrocytes are not connected to other cells by tight junctions, and they do not have a common basal membrane. Therefore, polar molecules (such as proteins) can enter the interstitial liquid and be directly transported to the pericytes and the endothelial cells (Goldstein, 1988). That astrocytes are important for the induction and maintenance of the BBB properties can be deduced from the following observations in cell cultures: in the presence of astrocytes or medium conditioned by astrocytes endothelial cells express markers important for BBB characteristics and develop tight junctions (Dehouck, 1990; Arthur, 1987; Tao-Cheng, 1987). On the other hand, endothelial cells promote the development and differentiation of astrocytes. This interaction between both cell types actually occurs even when there is no contact between the two cell types, indicating that some soluble, extracellular factors are mediators of BBB development.

Ciprofloxacin - Best antibiotic

        INTRODUCTION:

        Ciprofloxacin Hydrochloride is a second-generation fluoroquinolone antibiotic used to treat infections caused by bacteria      such as pneumonia; bronchitis; prostatitis, anthrax, chancroid; gonorrhea; endocarditis, gastroenteritis and ear, lung, throat, and urinary tract infections. Antibiotics will not work for colds, flu, or other viral infections. Chemically, Ciprofloxacin Hydrochloride is, 1-Cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinolinecarboxylic acid, monohydrochloride, monohydrate. Its molecular formula is C₁₇H₁₈FN₃O₃·HCl·H₂O, and it has a molecular weight of 385.82.After oral administration, Ciprofloxacin given as an oral tablet is rapidly and well absorbed from the gastrointestinal tract after oral administration. 

The absolute bioavailability is approximately 70% with no substantial loss by first pass metabolism. Ciprofloxacin maximum serum concentrations and area under the curve are shown in the chart for the 250 mg to 1000 mg dose range. 

The pharmacokinetics of Ciprofloxacin in the urine of pediatric patients has not been studied at this time. Until further data are available, the renal pharmacokinetic properties of Ciprofloxacin Hydrochloride established in adults should not be extrapolated to pediatric patients. Because Ciprofloxacin Hydrochloride is renaly excreted, the serum half-life is prolonged in patients with reduced renal function. 

INDICATION:

Ciprofloxacin is used to treat a number of infections, including infections of bones and joints, endocarditis, gastroenteritis, malignant otitis externa, respiratory tract infections, cellulitis, urinary tract infections, prostatitis, anthrax, and chancroid, as well as:

·         Urinary tract infections (recommended as a first-line antibiotic)

·         Chronic bacterial prostatitis (recommended as a first-line antibiotic choice)

·         Lower respiratory tract infections (not recommended as a first-line antibiotic choice)

·         Acute sinusitis (not recommended as a first-line antibiotic choice)

·         Skin and skin structure infections

·         Bone and joint infections

·         Infectious diarrhea

SIDE EFFECTS:

Diarrhea, fever, sore throat and headache, pale or yellowed skin, dark colored urine, fever, weakness, seizure (convulsions), nausea, vomiting, stomach, pain, dizziness, insomnia, numbness, tingling, or unusual pain anywhere in your body

CONSTITUENTS:

Active Substance:

Active ingredient of Xylobox Powder for Suspension 60 ml is Ciprofloxacin Hydrochloride.

CAS Registry Number: [86393-32-0]

               

 Physical Characteristics of Active Substance:

Ciprofloxacin Hydrochloride is a faintly yellowish to light yellow crystal. Sparingly soluble in water, slightly soluble in acetic acid and methanol, very slightly soluble in dehydrate alcohol, practically insoluble in acetone, in acetonitrile, in ethyl acetate, in hexane, and in methylene chloride.

Compatibility:

As the product is designed for single active substance the incompatibility with other active substances does not arise in this preparation. The active material, Ciprofloxacin Hydrochloride is not incompatible with other excipients used in the formulation. 

Cefpodoxime proxetil - Best Powder for suspension --- For Child

INTRODUCTION:

Cefpodoxime proxetil is a cephalosporin antibiotic used to treat infections caused by bacteria such as pneumonia; bronchitis; gonorrhea; and ear, lung, throat, and urinary tract infections. Antibiotics will not work for colds, flu, or other viral infections. Chemically, Cefpodoxime proxetil is, (6R,7R)-7-[(2Z)-2-(2-amino-1,3-thiazol-4-yl)-2-(methoxyimino)acetamido]-3-(methoxymethyl)-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid. Cefpodoxime proxetil is an orally absorbed broad spectrum third generation cephalosporin antibacterial. It is a prodrug that is de-esterified in vivo to its active metabolite, cefpodoxime. After single- and multiple-dose (12-hourly) administration of cefpodoxime proxetil in the therapeutic dose range of 100 to 400mg of cefpodoxime equivalents, average peak plasma concentrations of cefpodoxime range from 1.0 to 4.5 mg/L and occur between 1.9 and 3.1 hours after administration. The half-life of cefpodoxime ranges from 1.9 to 2.8 hours. The absolute bio-availability of cefpodoxime proxetil tablets is 50%, and absorption is enhanced by concomitant administration of food. Drug not absorbed is degraded in the gastrointestinal tract and excreted in the faeces. As expected for a drug eliminated primarily by renal excretion, the disposition of cefpodoxime is altered in patients with impaired renal function; the half-life increases, while apparent plasma clearance and renal clearance decrease. The pharmacokinetics of cefpodoxime after oral administration of cefpodoxime proxetil are not affected by age.

INDICATION:

Respiratory tract infections, for example, acute and chronic bronchitis, infected bronchiectasis, Acute bacterial pneumonia, lung abscess.

Ear, nose and throat infections, for example, sinusitis, tonsillitis and pharyngitis.

Urinary tract infections, for example, acute and chronic pyelonephritis, cystitis.

Cotitis media, Pharyngitis, and sinusitis.

Uncomplicated Skin and Skin Structure Infections

Uncomplicated Urinary Tract Infections.

SIDE EFFECTS:

Renal dysfunction, toxic nephropathy, hepatic dysfunction including cholestasis, aplastic anemia, hemolytic anemia, serum sickness-like reaction, hemorrhage, agranulocytosis, and pancytopenia.

Physical Characteristics of Active Substance:

Cefpodoxime proxetil is a white to light brownish-white powder, odorless or having faint odor, and has bitter test. very slightly soluble in water, soluble in acetonitrile and in methanol, freely soluble in dehydrated alcohol, slightly soluble in ether.

Mixing substances and its mechanism of Pharmaceutical Science

Mixing

Definition: Process that results in randomization of dissimilar particles within a system.

Mechanisms of mixing:
The most common classification of mixers however is based on the type of dosage form they are used to handle. A brief summary of mixing process in relation to the type of dosage form is presented below

1. Mixing for solids
Physical properties that effect the ease of mixing are:
(a) Material density
(b) Particle size and distribution
(c) Wettability
(d) Stickiness
(e) Particle shape / roughness

The most preferred types of mixers for solid mixing are Tumble mixers and Fixed shell mixers. Tumble mixers operate on the principle of bulk transport and shear. The mixing efficiency has a direct co-relation with the speed of rotation of tumble blender. Three types of most commonly used blenders are illustrated below:

A – Double cone blender, B – V blender and C – Bin blender

Fixed shell mixers are equipments in which the material is held in a stationary container and mixing is brought about by means of moving screws, paddles or blades. The ribbon blender consists of a relatively long trough like shell with a semicircular bottom, usually opening at the top and fitted with helical blades. The blades produce a continuous cutting and shuffling of charge by circulating the charged powder from end to end of the trough as well as rotationally.

2. Mixing of liquids
Mixing occurs in two stages:
(a) Localized mixing which applies sufficient shear to the particles of the fluid
(b) A general movement sufficient to take all parts of the material through the shearing zone and to ensure a uniform final product.

Mixing mechanisms fall essentially into four categories:

1. Bulk Transport – movement of a relatively large portion of material being mixed from one location in the system to another.

2. Turbulent flow – Characterized by the fluid having different instantaneous velocities at the same instant of time. The temporal and spatial velocity differences resulting from turbulence produce randomization of fluid particles.

3. Laminar Flow – Streamline flow that is encountered most commonly in highly viscous liquids.

4. Molecular diffusion – Primary mechanism responsible for mixing at the molecular level which results from the thermal motion of molecules.

Governed by Fick's fist law of diffusion,

dm/dt = - DA dc/dx
Where,
dm/dt – rate of transport of mass across a surface area
D – Diffusion Co-efficient
A – Area across which diffusion is occurring
dc/dx – Concentration gradient

Mixing as a process can either be carried batch to batch or can be continuous. Impellers, Air-jets, Fluid-jets and Baffle mixers are the major types of equipment used for batch mixing. Impellers operate using a combination of radial, axial and tangential flow. These might be classified into two further types, Propellers and Turbines, the former being used for low viscosity liquids while the latter for high viscosity ones.

3. Mixing of semi-solids
The mechanisms involved in mixing semi solids depend on the character of the material which may show considerable variation. Many semi solids form neutral mixtures having no tendency to segregate although sedimentation may occur.

Three most commonly used semi solid mixers are

(a)      Sigma blade mixer – Contains two blades which operate in a mixing vessel which has a double trough shape, the blades moving at different speeds towards each other. Used for products like granulation masses and ointments.

(b)      Triple-roller mill – The differential speed and narrow clearance between the roller develop high shear over small volumes of material. The roller mills are generally used to grind and complete the homogeneity of ointments.

(c)       Planetary mixers – it utilizes a mixing arm rotating about its own axis and also about a common axis usually the centre of the mixing wheel. The blades provide the kneading action, while the narrow passage between the blades and the wall of the can provides shear.

Mixer Selection

Factors to be taken into consideration while selecting a mixing equipment include,
(a) Physical properties of materials to be mixed such as density, viscosity and miscibility
(b) Economic considerations – operating efficiency, cost and maintenance

One of the first things to determine is if the process is intended to be a batch or a continuous process, each of which can have its advantages and drawbacks depending on the load to be used. Size is considered keeping in mind the optimal working volume, fill level and residence time. The optimal working volume would depend on the construction of the mixer. It generally lies between 50 to 70 percent of the maximum. Similarly, too much of fill would lead to low mixing and hence fill level becomes important. Residence time which is defined as the amount of time ingredients are in the mixer and is a particularly important determinant of the size of a continuous mixer. Choice of agitators determines the efficiency in breaking up lumps/agglomerates and serves to add shear aiding the final dispersion.

A brief table showing various agitator types and their respective uses in shown below.

1.      Ribbon - For Powders, granules, some slurries, mainly free flowing

2.      Paddle - For Powders, granules, some slurries, free flowing, light pastes

3.      Sigma - For Sticky materials, thick pastes and slurries

Important features of the gastrointestinal tract

Important features of the gastrointestinal tract

The following are some of the important features of the human gastrointestinal tract.

1. There is a copious blood supply.

2. The entire tract is lined with mucous membrane through which drugs may be readily transferred into the general circulation.

3. The interior surface of the stomach is relatively smooth.

4. The small intestine presents numerous folds and projections.

5. Approximately 8–10 L per day of fluids are produced or secreted into the gastrointestinal tract and an additional 1–2 L of fluid is obtained via food and fluid intake.

6. The gastrointestinal tract is highly perfused by a capillary network, which allows absorption and distribution of drugs to occur. This immediate circulation drains drug molecules into the portal circulation, where absorbed drugs are carried to the liver and may undergo first pass effect.

Omega-3 fatty acids

Omega-3 fatty acids

Omega-3 fatty acids (also called ω−3 fatty acids or n−3 fatty acids) are fats commonly found in marine and plant oils. They are polyunsaturated fatty acids with a double bond (C=C) starting after the third carbon atom from the end of the carbon chain. The fatty acids have two ends—the acid (-COOH) end and the methyl (-CH3) end. The location of the first double bond is counted from the methyl end, which is also known as the omega (ω) end or the n end.

Common sources of omega–3 fatty acids include fish oils, algal oil, squid oils, and some plant oils such as Sacha Inchi oil, echium oil, flaxseed oil and hemp oil.

Cancer

The evidence linking the consumption of fish to the risk of cancer is poor Supplementation with omega-3 fatty acids does not appear to affect this risk either.

A 2006 report in the Journal of the American Medical Association, in their review of literature covering cohorts from many countries with a wide variety of demographics, concluded that there was no link between omega−3 fatty acids and cancer.

Cardiovascular disease

Omega-3 fatty acids also have mild antihypertensive effects. When subjects consumed omega-3 fatty acids from oily fish on a regular basis, their systolic blood pressure was lowered by about 3.5–5.5 mmHg. The 18 carbon α-linolenic acid (ALA) has not been shown to have the same cardiovascular benefits that DHA or EPA may have. 

Omega-3 fatty acids in algal oil, fish oil, fish and seafood have been shown to lower the risk of heart attacks.

Inflammation

Although not confirmed as an approved health claim, current research suggests that the anti-inflammatory activity of long-chain omega−3 fatty acids may translate into clinical effects. For example, there is evidence that rheumatoid arthritis sufferers taking long-chain omega−3 fatty acids from sources such as fish have reduced pain compared to those receiving standard NSAIDs. Some potential benefits have been reported in conditions such as rheumatoid arthritis.

Developmental disorders

Although not supported by current scientific evidence as a primary treatment for ADHD, autism spectrum disorders, and other developmental differences, omega-3 fatty acids have gained popularity for children with these conditions. 

Omega-3 fatty acids offer a promising complementary approach to standard treatments for ADHD and developmental coordination disorder. Fish oils appear to reduce ADHD-related symptoms in some children. Double blind studies have shown "medium to strong treatment effects of omega 3 fatty acids on symptoms of ADHD".

Psychiatric disorders

Though there is some evidence that omega-3 fatty acids are related to a variety of mental disorders. They may tentatively be useful as an add-on for the treatment of depression associated with bipolar disorder and there is preliminary evidence that EPA supplementation are helpful in cases of depression. There however is a significant risk of bias in the literature.

 

Cognitive aging

Epidemiological studies suggest that consumption of omega-3 fatty acids can reduce the risk of dementia, but evidence of a treatment effect in dementia patients is inconclusive. However, clinical evidence suggests benefits of treatment specifically in patients who show signs of cognitive decline but who are not sufficiently impaired to meet criteria for dementia.

 

List of omega−3 fatty acids

This table lists several different names for the most common omega−3 fatty acids found in nature.

Common name	Lipid name	Chemical name
Hexadecatrienoic acid (HTA)	16:3 (n−3)	all-cis-7,10,13-hexadecatrienoic acid
α-Linolenic acid (ALA)	18:3 (n−3)	all-cis-9,12,15-octadecatrienoic acid
Stearidonic acid (SDA)	18:4 (n−3)	all-cis-6,9,12,15-octadecatetraenoic acid
Eicosatrienoic acid (ETE)	20:3 (n−3)	all-cis-11,14,17-eicosatrienoic acid
Eicosatetraenoic acid (ETA)	20:4 (n−3)	all-cis-8,11,14,17-eicosatetraenoic acid
Eicosapentaenoic acid (EPA)	20:5 (n−3)	all-cis-5,8,11,14,17-eicosapentaenoic acid
Heneicosapentaenoic acid (HPA)	21:5 (n−3)	all-cis-6,9,12,15,18-heneicosapentaenoic acid
Docosapentaenoic acid (DPA), Clupanodonic acid	22:5 (n−3)	all-cis-7,10,13,16,19-docosapentaenoic acid
Docosahexaenoic acid (DHA)	22:6 (n−3)	all-cis-4,7,10,13,16,19-docosahexaenoic acid
Tetracosapentaenoic acid	24:5 (n−3)	all-cis-9,12,15,18,21-tetracosapentaenoic acid
Tetracosahexaenoic acid (Nisinic acid)	24:6 (n−3)	all-cis-6,9,12,15,18,21-tetracosahexaenoic acid

The omega−6 to omega−3 ratio (Most Important)

Some clinical studies indicate that the ingested ratio of omega−6 to omega−3 (especially linoleic vs alpha-linolenic) fatty acids is important to maintaining cardiovascular health. However, two studies published in 2005 and 2007 found that while omega−3 polyunsaturated fatty acids are extremely beneficial in preventing heart disease in humans, the levels of omega−6 polyunsaturated fatty acids (and therefore the ratios) were insignificant. 

Both omega−6 and omega−3 fatty acids are essential; i.e., humans must consume them in the diets. Omega−6 and omega−3 eighteen-carbon polyunsaturated fatty acids compete for the same metabolic enzymes, thus the omega−6:omega−3 ratio of ingested fatty acids has significant influence on the ratio and rate of production of eicosanoids, a group of hormones intimately involved in the body's inflammatory and homeostatic processes which includes the prostaglandins, leukotrienes, and thromboxanes, among others.

This necessitates that omega−6 and omega−3 be consumed in a balanced proportion; healthy ratios of omega−6:omega−3, according to some authors, range from 1:1 to 1:4 (an individual needs more omega−3 than omega−6). Other authors believe that ratio 4:1 (when the amount of omega-6 is only 4 times greater than that of omega-3) is already healthy. Studies suggest the evolutionary human diet, rich in game animals, seafood, and other sources of omega−3, may have provided such a ratio.

Daily values

As macronutrients, fats are not assigned Dietary Reference Intakes. Macronutrients have acceptable intake (AI) levels and acceptable macronutrient distribution ranges (AMDRs) instead of RDAs. The AI for omega−3 is 1.6 grams/day for men and 1.1 grams/day for women, while the AMDR is 0.6% to 1.2% of total energy.

Grams of omega−3 per 3oz (85g) serving
Common name	grams omega−3
Herring, sardines	1.3–2
Mackerel: Spanish/Atlantic/Pacific	1.1–1.7
Salmon	1.1–1.9
Halibut	0.60–1.12
Tuna	0.21–1.1
Swordfish	0.97
Greenshell/lipped mussels	0.95
Tilefish	0.9
Tuna (canned, light)	0.17–0.24
Pollock	0.45
Cod	0.15–0.24
Catfish	0.22–0.3
Flounder	0.48
Grouper	0.23
Mahi mahi	0.13
Orange roughy	0.028
Red snapper	0.29
Shark	0.83
King mackerel	0.36
Hoki (blue grenadier)	0.41
Gemfish	0.40
Blue eye cod	0.31
Sydney rock oysters	0.30
Tuna, canned	0.23
Snapper	0.22
Eggs, large regular	0.109
Barramundi, saltwater	0.100
Giant tiger prawn	0.100
Lean red meat	0.031
Turkey	0.030
Cereals, rice, pasta, etc.	0.00
Fruit	0.00
Milk regular	0.00
Regular bread	0.00
Vegetables	0.00