Alkaloids and Their Extraction

Organic nitrogen-containing compounds found in plants, often possessing potent physiological effects. They are typically bitter, crystalline, and soluble in organic solvents.

The process involves extracting the alkaloids from plant sources using appropriate solvents, separating them into individual compounds through techniques like chromatography, and often liberating the free base.

Alkaloids are usually colorless, crystalline solids, soluble in organic solvents like ether and chloroform, but typically insoluble in water. Some are liquids and a few have color, like berberine, which is yellow. Most alkaloids have a bitter taste and are optically active.

The nitrogen in alkaloids is often found in a tertiary amine, sometimes within a ring system. They also commonly contain oxygen.

Methods used to determine the structure of alkaloids include: 1) Qualitative and quantitative analysis for the molecular formula. 2) Examining the functional groups of oxygen and nitrogen. 3) Examining the presence of unsaturation and other functional groups by chemical reactions. 4) Using physical methods like IR, UV, NMR, and mass spectrometry.

This method involves treating the alkaloid with methyl iodide, followed by silver hydroxide and heat. This process breaks open heterocyclic rings, eliminating nitrogen and revealing the structure of the carbon skeleton.

The major groups include: Phenylethylamine, Pyrrolidine, Pyridine-piperidine, Pyrrolidine-pyridine, Quinoline, Isoquinoline, Phenanthrene, and Indole.

A colorless solid that melts at 38°C and is found in Ephedra plants. Its physiological action is similar to adrenaline, and it can be taken orally.

Ephedrine is oxidized to benzoic acid, indicating the presence of a benzene ring with one side chain. It forms a nitroso compound, indicating an imino group (secondary amine). It forms a dibenzoyl derivative, indicating a hydroxyl group. It undergoes hydramine fission, forming methyl amine and propiophenone. These reactions help determine the structure of ephedrine.

Adrenaline, also known as epinephrine, is a hormone produced by the adrenal medulla. It is a colorless crystalline solid that raises blood pressure and is used to stop bleeding.

Adrenaline's solubility in sodium hydroxide and reprecipitation by carbon dioxide suggests phenolic properties. The green color with ferric chloride confirms a catechol derivative. Upon boiling with potassium hydroxide, it releases methyl amine, indicating a methyl amino group. Fusion with potassium hydroxide yields protocatechuic acid. These reactions provide clues about the structure of adrenaline.

A liquid alkaloid boiling at 193°C. It is found in coca plants.

Hygrine's reactivity indicates the presence of a ketone group and a tertiary nitrogen. Oxidation with chromic acid yields hygrinic acid. Dry distillation of hygrinic acid results in N-methyl pyrrolidine, suggesting a pyrrolidine ring. The detailed structure is confirmed by synthesis.

A liquid alkaloid boiling at 166°C, found in hemlock.

Distillation of coniine with zinc dust yields conyrine. Oxidation of conyrine with potassium permanganate gives pyridine-2-carboxylic acid, indicating a pyridine nucleus. Heating with hydroiodic acid forms n-octane, suggesting a propyl side chain. These reactions provide clues about the structure of coniine.

A solid alkaloid melting at 128°C, found in pepper.

Piperine is hydrolyzed by alkali into piperic acid and piperidine, indicating an amide structure. Piperic acid contains one carboxylic group and two double bonds. Oxidation of piperic acid produces piperonal and piperonylic acid, suggesting a benzene derivative. These reactions provide information about the structure of piperine.

A liquid alkaloid, the main active ingredient in tobacco. It is the best known and most widely distributed tobacco alkaloid.

Oxidation of nicotine with potassium permanganate forms nicotinic acid, indicating a pyridine nucleus. Distillation with zinc chloride yields pyridine, pyrrole, and methyl amine, suggesting a pyrrolidine side chain. Heating with hydroiodic acid produces methyl iodide, confirming a methyl group attached to the side chain. These reactions provide clues about the structure of nicotine.

A solid alkaloid melting at 90°C, isolated from angostura bark.

Cusparine is found to contain one methoxy group. Fusion with potassium hydroxide produces protocatechuic acid. Controlled oxidation yields piperonylic acid and 4-methoxyquinoline-2-carboxylic acid, suggesting a quinoline derivative. These reactions provide clues about the structure of cusparine.

A group of alkaloids found in opium, which are classified into two main categories based on their structure: Isoquinoline group (e.g., papaverine) and Phenanthrene group (e.g., morphine).

A solid alkaloid melting at 147°C, and optically inactive. It belongs to the isoquinoline group of opium alkaloids.

Papaverine forms a quaternary iodide, indicating a tertiary nitrogen atom. The Zeisel method indicates four methoxy groups. Oxidation with permanganate yields papaverinol and papaveraldine, suggesting a methylene group. Further oxidation breaks it down into fragments like veratric acid and 6,7-dimethoxyisoquinoline-1-carboxylic acid, confirming the presence of an isoquinoline ring. These reactions provide clues about the structure of papaverine.

The chief alkaloid found in opium, a solid that melts at 254°C.

Morphine forms a diacetate (heroin) and dibenzoate, indicating two hydroxyl groups, one of which is phenolic. It can be converted to a monohalogeno derivative, suggesting a secondary alcoholic hydroxyl group. These characteristics provide clues about the structure of morphine.

A solid alkaloid melting at 146°C, found in barley mutants. It has a stimulatory effect on blood pressure.

A solid coca alkaloid melting at 98°C, found in coca leaves. It is used as a local anesthetic.

Cocaine undergoes hydrolysis to methanol and benzoylecgonine, suggesting a carbomethoxy group. Further hydrolysis of benzoylecgonine yields benzoic acid and ecgonine. The structure of ecgonine is confirmed by synthesis. These reactions provide clues about the structure of cocaine.

The alkaloids A, B, and C are representative of the general classes of alkaloids and their structural complexity. Identifying the specific structures of these alkaloids requires understanding the reactions involved in their determination. The synthesis of the alkaloids is the key process to confirming their structure.