4. Ergot alkaloids
Ergot alkaloids contain:
Ergot is the product of the fungus (Claviceps purpurea)that grows up on rye and other grains.
5. Opium alkaloids
Opium is obtained from the milky juice derived from the unripe seed capsule of the poppy plant (Papaver somniferum). This includes at least 20 alkaloids of which the ones having clinical importance are:
6. Rauwolfia alkaloids:
The examples of rauwolfia alkaloids are:
7. Xanthine alkaloids
Xanthine alkaloids include:
That's all about alkaloids for now. Now let's move on to Glycosides!
What is glycoside? Glycosides are non-nitrogenous, colorless, crystalline solids that splits up into sugar (one to four molecules) and non-sugar parts. They do not form salts. Some are poisonous.
The non-sugar part of glycosides is termed aglycone or genin. Aglycone is made of cyclopentanoperhydrophenanthrene nucleus (steroid nucleus) to which is attached an unsaturated lactone ring at C17 (17th number carbon atom). It is chemically related to bile acid, sterol and steroid hormones.
The pharmacological activity of glycoside resides in the aglycone part. However, the combination of sugar to the aglycone modifies the lipid/water partition coefficient, potency, and pharmacokinetic properties.
Aglycone can be separated from the sugar part of glycosides by adding an acid or enzyme.
Classification of glycosides
Glycoside is classified as glucoside, glalactoside, fructoside according to the presence of glucose, galactose and fructose respectively as sugar.
Glycoside is widely distributed in the bark, seed and leaf of the plant.
Some important glycosides are:
Digoxin and digitoxin (isolated from the leaves of purple foxgloves Digitalis purpurea) are called digitalis cardiac glycosides. They have powerful action on the myocardium.
Salicylic acid (orthohydrobenzoic acid) was obtained first from salicin, a glycoside bitter in taste found in the willow bark in 1838. On hydrolysis, salicin yields glucose and salicylic alcohol. Salicylic alcohol is then converted into salicylic acid.
The aminoglycosides contains glycosidic bond (-O-) in its structure but it is NOT considered as glycoside.
Oils used as drug are of two kinds: fixed and volatile.
Fixed oil is a mixture of glycerol esters of high molecular weight aliphatic acid especially palmitic, stearic, and oleic acid. It is non-volatile and lighter than water as well as insoluble in water. But it is soluble in chloroform and ether. It is not dissipated by heat.
Examples of fixed oils are olive oil, castor oil, and chaulmoogra oil. Metabolites of castor oil irritate the mucosa of gastrointestinal tract producing peristalsis leading to evacuation and are used as cathartic.
Olive oil is usually edible and can be used as emollient.
Volatile oil is the odorous principle found in various parts of plant. Since it evaporates when exposed to air at room temperature, it is called volatile or essential oil. The term essential is used because volatile oil represent the essence or odoriferous constituent of the plant.
Volatile oil is colorless when fresh, but on standing it may be oxidized and resinified, thus its color is converted to dark. So, it should be stored in cool, dry place in tightly stoppered, preferably amber glass container. Chemically, it usually contains the hydrocarbon tarpene or some polymer of it. The terpene fraction serves as diluent for the more active compound present.
Examples of volatile oils are Peppermint oil, spearmint oil, clove oil, wintergreen oil, and lemon oil.
The active portion of peppermint oil is menthol. In case of clove oil, the active component is eugenol. Clove oil relieves pain when applied locally (in case of toothache). Wintergreen oil is used locally in the relief of joint pain. Peppermint and spearmint oils are used as solvent and flavor in the compounding of prescription.
D. Gums and mucilage
Gum is a secretory hydrocarbon product of plant origin. Chemically, it is anionic or nonionic polysaccharide or slat of polysaccharide which on hydrolysis produces sugar.
An effort has been made to distinguish between the gum and mucilage on the basis that gum readily dissolves in water, whereas mucilage forms slimy mass.
Examples of natural gums include Agar and psyllium seed. When they are swallowed, they absorb water to from bulk, and exert a laxative effect.
An example of mucilage isTragacanth, which is used as:
A suspending agent for insoluble powder in mixture
An emulsifying agent for oil and resin
E. Carbohydrate and related compounds
Carbohydrate constituents a major class of naturally occurring organic compound.
The carbohydrate sucrose and other sugars like dextrose and fructose are used in many circumstances. For example:
Sucrose is used as a demulcent and nutrient
Sucrose in sufficient concentration (65%) in aqueous solution, is bacteriostatic and preservative
Dextrose is a nutrient and may be given by mouth or by intravenous injection as required.
Dextrose is used as an ingredient in many preparation such as dextrose in aqua and dextrose in saline.
Dextrose is used as an ingredient of anticoagulant such as dextrose citrate sodium, citrate phosphate dextrose solution, etc. These solutions are used for the storage of whole blood.
Fructose is used for food for diabetic patients and may be of particular benefit in diabetic acidosis.
A carbohydrate related compound, Alcohol (70%) is used as an antiseptic.
So there you go, I have discussed the whole of plant sources of drugs for you! Now, it's time to move on to the animal sources!