Definition of alkaloid in English:



  • Any of a class of nitrogenous organic compounds of plant origin which have pronounced physiological actions on humans. They include many drugs (morphine, quinine) and poisons (atropine, strychnine).

    • ‘Other important alkaloids are caffeine, ricinine, and quinine.’
    • ‘Morphine is an alkaloid, meaning that it is an organic compound that contains carbon, hydrogen and nitrogen, and forms a water-soluble salt.’
    • ‘This material is a complex mixture of about 20 different alkaloids or nitrogen containing organic bases.’
    • ‘The cinchona tree contains more than 20 alkaloids of which quinine and quinidine are the most important.’
    • ‘Barbiturates are derived from barbituric acid, an alkaloid with nitrogen-containing rings.’
    • ‘Caffeine is a naturally occurring drug belonging to a group of compounds called alkaloids.’
    • ‘The isolation of morphine from opium takes advantage of the amphoteric nature of the alkaloid, since morphine is a phenolic amine.’
    • ‘Key alkaloids present in goldenseal include berberine, hydrastine, and canadine.’
    • ‘The alkaloids in poppy include morphine, narcotine and codeine - the reasons why opium is used most frequently as a sedative.’
    • ‘Many multicellular trichomes are glandular, developing a terminal gland which may secrete a variety of compounds, such as alkaloids to deter or poison predators.’
    • ‘Caffeine is a bitter alkaloid found especially in coffee, tea, and kola nuts and used medicinally as a stimulant and diuretic.’
    • ‘CE analysis of plant secondary metabolites such as flavonoids, alkaloids, and phenolic acids is now common.’
    • ‘Plant or vinca alkaloids are derived from plants and block cell division during mitosis.’
    • ‘Second, the alkaloid is refluxed with acetic anhydride for about five hours.’
    • ‘They are precursors of benzoic phenanthridine alkaloids, active ingredients of many medicinal plant extracts.’
    • ‘At present, the chemical components of this water extract are thought to include only alkaloids, terpenes and pigments.’
    • ‘Berberine is an alkaloid occurring in the plant genera Berberis and Coptis.’
    • ‘Prominent examples are quinolizidine alkaloids, gossypol, glucosinolates, nonproteinogenic amino acids and furanocoumarins.’
    • ‘Terpenoid indole alkaloids absorb UV radiation and are implicated as having a UV-protective role in plants.’
    • ‘Diuretics can be found in terpenes, phenolics and alkaloids.’


Early 19th century coined in German from alkali.