No abstract

Isoguanosine (oxyadenosine or crotonoside), previously known to occur in nature only in the croton bean, was isolated from an animal, the marine nudibranch mollusk Diaulula sandiegensis.

A new N-methylpurine riboside (doridosine), probably N1-Methylisoguanosine, was isolated from the digestive glands of a nudibranch. Doridosine produces prolonged hypotension and bradycardia in anesthetized rats, decreases the rate and the amplitude of contraction of guinea pig atria in vitro, and causes the heart rate in anesthetized mice to be reduced by 50 percent for many hours after which the animals recover completely.

A potent, dialyzable toxin (atelopidtoxin) occurs in the skin of frogs of the genus Atelopus. A concentrate of atelopidtoxin from Atelopus zeteki has an LD(50) in mice of 16 micrograms per kilogram. It differs from batrachotoxin, tetrodotoxin, and saxitoxin, the only known nonprotein substances of greater toxicity, as well as from all toxins previously isolated from amphibia.