Natural products

Natural products are specific chemical compounds which are produced and secreted by living creatures. There is no mean of any human intervention in the production processes of these products. Some people may get confused purification or extraction with production. Simply because purification or extraction are processes done by humans to obtain these natural products from their sources in a concentrated form. Some natural products may undergo certain modifications to obtain specific function so that these products are called semi-synthesized. However, synthesized products are those completely designed in laboratories and research institutes. There are many types of natural products; such as Carbohydrates, Glycosides, Lipids, Proteins, Alkaloids, Volatile oils, Prostaglandins, Plants exudate and Herbal medicines. 

These small molecules provide the source or inspiration for the majority of FDA-approved agents and continue to be one of the major sources of inspiration for drug discovery. In particular, these compounds are important in the treatment of life-threatening conditions. Many of these products are either official in the USP,  listed in the Food Chemical Codex (FCC) or generally used in pharmacy. 

CARBOHYDRATES:

It is one of the important groups of organic natural products. Carbohydrates embrace A) Aliphatic polyhydric  alcohols whether primary alcohols, which are oxidized into Aldehydes [R-CHO], or secondary alcohols, which are oxidized into Ketones [R-CO-R]. Those types of Carbohydrates produce monosaccharides (simple sugars); Aldoses and Ketoses and B) condensation products which are saccharides anhydride; disaccharides trisacchardes.. and so on. Polysaccharides, on the other hand, contain many monosaccharide units joined in long linear or branched chains. Polysacchrides have 2 major biological functions: as storage form for fuel and as structural elements. The di-, tri- and up to about the  decasacchrides sometimes are grouped together under the term Oligosacchrides. 
The total scheme for the Aldoses and the Ketoses is shown in the following table:

Ref: Remington 1-The Science and Practice of Pharmacy (20th Ed)

For more details on Carbohydrates structures, cyclic structures and Nomenclature check the following link:

http://www.chem.qmul.ac.uk/iupac/2carb/

Official Carbohydrates:

1.Monosaccharides: Dextrose [D-glucose] and Fructose are the only monosaccharides that occur in the free state to any important extent as well as they are present in the juices of many ripe fruits. 

2.Disaccharides: Lactose [milk sugar] and Sucrose [cane or beet sugar].

3.Polysaccharides: Dextrin, Collagen, Inulin, Starch, Cellulose and Rice starch. 

Inulins are a group of naturally occurring polysacchrides produced by many types of plants.They belong to a class of dietary fibers. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes. Most plants that synthesize and store inulin do not store other forms of carbohydrate such as startch.

Inulin and its analog Sinistrin are used to help measure kindney function by determining the glomerular filtration rate  (GFR). GFR is the volume of fluid filtered from the renal (kidney) glomerular capillaries into the Bowman's capsule per unit time. Inulin is not secreted or reabsorbed in any appreciable amount at the nephron allowing GFR to be calculated. However, due to clinical limitations, Inulin and Sinistrin although characterised by better handling features are rarely used for this purpose and Creatinine values are the standard for determining an approximate GFR. It is also used for rehydration and remineralization following important loss of water, like diarrhea and diaphoresis. Inulin can also be used as a vaccine adjuvant.

Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen. Dextrins are mixtures of polymers of D-glucose units linked by α-(1→4) or α-(1→6) glycosidic linkage. Cyclodextrins are produced from starch by means of enzymatic conversion. They are used in food, pharmaceutical, drug delivery, and chemical industries. Cyclodextrins are able to form host-guest complexes with hydrophobic molecules given the unique nature imparted by their structure. As a result, these molecules have found a number of applications in a wide range of fields. One example is Sugammadex, a modified γ-cyclodextrin which reverses neuromuscular blockade by binding the drug Rocuronium. Other than the above mentioned pharmaceutical applications, cyclodextrins can be employed in environmental protection: these molecules can effectively immobilise inside their rings toxic compounds, like Trichloroethane or heavy metals, or can form complexes with stable substances, like Trichlorfon (an organophosphorus insecticides) or sewage sludge, enhancing their decomposition.

4.Natural products: Other than mentioned above are Acacia, Agar, Pectin, Plantago seed and Tragancanth. 

Dietary fiber: 

Dietary fiber  is the indigestible portion of plant foods having two main components:

• soluble (prebiotic or viscous) fiber that is readily fermented in the colon into gases and physiologically active byproducts.
• insoluble fiber that is metabolically inert, absorbing water as it moves through the digestive system, easing defecation.

Plant sources of fiber

Soluble fiber is found in varying quantities in all plant foods, including:

• Legumes (peas, soybeans, lupins and other beans)
• Oats, Rye, Chia, and Barely
• Some fruits and fruit juices (including prune juice, plums, berries, bananas, and the insides of apples and pears)
• Certain Vegetables such as Broccoli, Carrots, and Jerusalem artichokes.
• Root tubules and root vegetables such as sweet potatoes and Onions (skins of these are sources of insoluble fiber also)
• Psyllium seed husk (a mucilage soluble fiber) and flax seeds
• Nuts, with Almonds being the highest in dietary fiber

Sources of insoluble fiber include:

• Whole grain foods
• Wheat and Corn bran
• nuts and seeds
• Potato skins
• Hemp seed
• Lignans
• vegetables such as green beans, cauliflower, zucchini (courgette), celery, and nopal.
• some fruits including avocado, and unripe bananas.
• the skins of some fruits, including Kiwifruit and tomatoes.

Ref: http://en.wikipedia.org/wiki/Dietary_fiber

GLYCOSIDES:

Glycosides may be defined broadly as condensation products of sugars with various kinds of organic hydroxy compounds. The nonsugar portion is termed aglycone,or aglycon, or agenin. Glycosides undergo hydrolysis yielding  sugar and nonsugar moieties. In general , the hydrolysis is  catalysed energetically by protons ( in lab we may use dilute acids). Acid hydrolysis occurs whether the Glycosidic linkage is alpha or beta. In addition to acid hydrolysis, nature produces many enzyme to catalyse the hydrolysis. That enzymatic catalyses is quite specific. It should be noted that there are 2 enzymes , namely Emulsin of Almond kernels and Myrosin of black mustard seeds, each of which has the ability to hydrolyse a considerable number of Glycosides. The enzymes frequently occur in the same plant along with Glycosides, but usually in different cells. Glycosides that are derivatives of Rhamnose require a special enzyme known as Rhamnase for their hydrolysis.

List of common Glycosides:

Ref: Remington 1-The Science and Practice of Pharmacy (20th Ed)

Many naturally occurring compounds not usually classed among the Glycosides actually contain glycosidic linkage in their structure. For instance, Gentamycin, Amikacine, Netilmicin, Tobramycin, Novobiocin, and Streptomycin among the antibiotics, Solanine and various other alkaloids (Glucoalkaloids), and nucleosides (consist of purine or pyrimidine base linked with D-ribose or D-2-deoxyribose).

LIPIDS:


The lipids are the fat and fat-like substances that occur in plants and animals. Like the carbohydrates and proteins, the lipids constitute a very important group of organic substances from the standpoint of physiological use. The lipids may be divided into 5 classes according to their chemical structure:

1. Fixed oils and fat [ester of Glycerol and fatty acids] - Olive oil and Lard
2. Waxes [esters of high-molecular-weight, monohydric alcohols and high-molecular-weight fatty acids] - Spermaceti 
3. Sterols [ alcohols containing  the CYCLOPENTANOPHENANTHEREN, steroids, nucleus] - Cholesterol and Ergosterol 
4. Phospholipids (phosphatides) [esters consisting of Glycerol in combination with fatty acids, phosphoric acid and certain nitrogenous compounds] - Lecithins 
5. Glycolipids (Cerebrosides) These substances are isolated from the brain and from various other sources that, on hydrolysis, yield fatty acids, Galactose, and the nitrogenous compound Sphingosine.

Fixed oils and fats

Fixed oils and fats are mixtures of Glyceryl esters of the so-called high fatty acids  [higher molecular weight aliphatic acids], especially Palmitic, Stearic, and Oleic acids.