Alkynes: Occurence and Importance
Small amounts of alkynes are found in crude oil and natural gas. However, alkynes found in nature in plants and in some animals possess physiological functions.
As an example, ichthyotherol is the active component in poisoned arrowheads used by Amazon Indians. Isolated from the secretions of skin glands of a poison dart frog, it causes convulsions in mammals.
Frequently, drugs are purposely designed to contain triple bonds because they are more active, less toxic and more easily absorbed by organisms than the corresponding alkanes or alkenes. For example, 3-methyl-pent-1-yn-3-ol is sold in the USA as an over-the-counter sleeping medicine. Numerous other alkynols show a similar mode of action.
The contraceptive 17-ethinylestradiol represents another example where the alkinyl-substituted derivative shows higher activity than the natural hormone.