alkaloid

noun

al·​ka·​loid ˈal-kə-ˌlȯid 

: any of numerous usually colorless, complex, and bitter organic bases (such as morphine or caffeine) containing nitrogen and usually oxygen that occur especially in seed plants and are typically physiologically active

alkaloidal

ˌal-kə-ˈlȯi-dᵊl 

adjective

Examples of alkaloid in a Sentence

Recent Examples on the Web

Mitragynine is a naturally occurring alkaloid that can be isolated from the leaves of Mitragyna speciosa, a medicinal plant also known as kratom, according to the National Center for Biotechnology Information’s National Library of Medicine. — Althea Legaspi, Rolling Stone, 17 Sep. 2026

Mitragynine is an alkaloid that occurs in trace amounts in the leaves of the kratom tree, Mitragyna speciosa, prevalent in Southeast Asia. — Theresa Braine, New York Daily News, 16 Sep. 2026

Many scientists believe the drug’s primary neuroactive alkaloid, called arecoline, is only noticeable after chewing betel nuts processed with slaked lime. — Andrew Paul, Popular Science, 10 Sep. 2026

No self-respecting living thing would deliberately sniff, let alone eat, any part of the plant, which also contains highly toxic steroidal alkaloids. — ABC News, 8 Sep. 2026

Word History

First Known Use

1820, in the meaning defined above

Rhymes for alkaloid

• adenoid
• amoeboid
• amyloid
• aneroid
• arachnoid
• asteroid
• benzenoid
• carcinoid
• celluloid
• coronoid
• humanoid
• mongoloid

Medical Definition

alkaloid

noun

al·​ka·​loid ˈal-kə-ˌlȯid 

: any of numerous usually colorless, complex, and bitter organic bases (as morphine or caffeine) containing nitrogen and usually oxygen that occur especially in seed plants and are typically physiologically active

alkaloidal

ˌal-kə-ˈlȯid-ᵊl 

adjective