alkaloides

Alkaloids are a diverse group of naturally occurring nitrogen-containing organic compounds, most of which are basic and contain heterocyclic ring structures. They are produced mainly by plants as secondary metabolites, though some occur in fungi, bacteria, and animals. Alkaloids often have pronounced physiological effects in humans and other animals, which has led to widespread medical, pharmaceutical, and recreational use. They are typically bitter-tasting and biologically active even at low concentrations.

Chemical and biosynthetic features vary across alkaloids. Most contain one or more nitrogen atoms within a ring system and are derived from amino acids such as tryptophan, tyrosine, phenylalanine, ornithine, or lysine. Structural classes include indole, isoquinoline, tropane, piperidine, pyridine, and xanthine alkaloids. Representative examples encompass morphine and codeine (phenanthrene-type), quinine (quinoline-type), atropine (tropane-type), nicotine (pyridine/tropane-type), caffeine (xanthine), and cocaine (tropane-type).

Occurrence, sources, and uses vary widely. The most famous sources are plants, notably Papaver somniferum (poppies), Cinchona species, and Solanaceae members such as Atropa belladonna and Nicotiana species. Due to their potent effects, alkaloids have long been used as medicines (analgesics, stimulants, anticholinergics, antimalarials) and, in some cases, as poisons. Many alkaloids are tightly regulated because of toxicity or potential for abuse.

Classification in this context is chemical rather than taxonomic; alkaloids form a broad category defined by structure and nitrogen-containing features. Ongoing research surrounds biosynthesis, ecological roles, medicinal chemistry, and production methods in plants and engineered systems.