Alkaloid

Alkaloids are a class of nitrogen-containing physiologically active natural compounds, most of which have more complex nitrogen heterocyclic structures and a few are non-nitrogen heterocyclic organic amines. Generally, it has a similar nature to alkali. It was translated as "muscarine" in the early years. Certain vitamins, amino acids, peptides, etc. from natural sources are also nitrogen-containing compounds, but are not routinely included in the alkaloid category. In fact, the term alkaloid has not yet been strictly and precisely defined. Alkaloids are widely distributed in nature, especially in the plant kingdom. There are also animal kingdoms, such as bufotenine in the glutinous rice, and hypoxanthine in the earthworm. According to statistics, at least 140 alkaloids have been found in plants, especially Papaveraceae, Anti-family, Solanaceae, Leguminosae, Oleaceae, Ranunculaceae, and Polygonaceae. In general, alkaloids are mostly distributed in dicotyledons, few in monocots, and few in gymnosperms and ferns or lower plants. Alkaloid-containing plants often contain a variety of alkaloids with similar chemical structures. Plants of similar genus have similar structures and some of the same alkaloids. There are several classification methods for alkaloids, which can be classified according to plant source, physiological effect or chemical structure, while the latter is more reasonable. Common types include azoles, pyridines, quinolines, isoquinolines, anthracenes, imidazoles, anthraquinones, decanes, anthracenes, steroids, and organic amines. The classification of alkaloids into 59 types is sufficient to illustrate the complexity of their structure. Alkaloids are mostly crystalline solids except for a few which are liquid at room temperature. Generally colorless, bitter, optically active, and mostly left-handed. It is alkaline, and its basic strength is significantly related to the molecular structure, especially the binding state of nitrogen atoms. The quaternary ammonium alkaloids are strongly alkaline, and the tertiary amines and secondary amine alkaloids are medium or strong bases or weakly alkaline. Some alkaloid molecules have a phenolic or carboxyl group and thus have an acid-base amphoteric reaction. Most of the alkaloids in plants are combined with organic acids to form salts, or saccharides are condensed into hydrazines, and a few alkaline alkaloids are present in a free state. The alkaloid salt is alkalized, and the alkaloid hydrazine is hydrolyzed to obtain a free base. Most alkaloids are insoluble or poorly soluble in water, soluble in organic solvents such as benzene, chloroform, ether, acetone, ethanol, and soluble in dilute acid to form salts. Alkaloid salts are mostly soluble in water and alcohol, insoluble or poorly soluble in organic solvents. Alkaloids can react with some reagents such as potassium cesium iodide, potassium iodide, potassium iodide or potassium iodide to form precipitates of different colors, which are commonly used to detect alkaloids. There are many methods for extracting alkaloids. Generally, the pulverized sample is first extracted with water, dilute acid water or ethanol, and the extract is concentrated. After alkalization, the total alkaloid is extracted with an organic solvent. Alternatively, the pulverized sample is first alkalized, and the total alkaloid is proposed using an organic solvent. The total base is isolated by various methods such as chromatography, preparation of derivatives, and the like. A small number of volatile or sublimable alkaloids can be purified by steam distillation or sublimation. Although the alkaloid content in plants is small, it is closely related to humans. It has long been recognized by humans that some alkaloid-containing plants or crude extracts can treat diseases or act as poisons. Since 1806, Serturner has isolated morphine from opium poppy. More than 6,000 alkaloids have been isolated from plants and animals, and nearly one hundred have been used or tested in clinical practice. Many alkaloids are good medicines for treatment. For example, berberine in the rhizome of Ranunculaceae is the main component of berberine, which has antibacterial and anti-inflammatory effects; reserpine in Rauvolfia can lower blood pressure; Garlander in Lycoris Sensitive effect on sequelae of poliomyelitis, morphine base contained in poppy peel is a famous analgesic; quinine is a valuable antipyretic; cephalosporin and vinblastine are good drugs for cancer; colchicine ( Alkali) can be artificially mutagenized to produce polyploids. Some alkaloids can be used to make pesticides for agriculture. Alkaloids have also been isolated in vertebrates and invertebrates, some of which are associated with the plants they consume, and the alkaloids found in cockroaches, mites and certain fish are true animal metabolites. .