[On the history of vitamin K, dicoumarol and warfarin]. / Pionerer bag vitamin K, dikumarol og warfarin.

The history of the discovery and development of vitamin K and its antagonists, the oral anticoagulants dicoumarol and warfarin, are fascinating, triumphant landmarks in the annals of medicine. Vitamin K was found by Carl Peter Henrik Dam and Fritz Schønheyder from the University of Copenhagen. The discovery was initiated by Dam, by a lucky choice of chicks in the dissertation of sterol metabolism, since the vitamin is not formed by intestinal bacteria in these animals. In these experiments the lack of an unknown factor in the synthetic diet caused internal bleeding similar to that found in scurvy, but the bleeding was not reversed by vitamin C and it could not be explained by the lack of classical vitamins. In 1935 the unknown antihaemorrhagic factor was named vitamin K and a few months later the phenomenon was also observed by H.J. Almquist and E.L.R. Stokstad in Berkeley. The activity of the factor was determined by bioassay in different extracts of green vegetables and alfalfa by Dam and Schønheyder. Vitamin K was isolated in 1939 by Dam and Paul Karrer in Zurich and the structure was determined by Edward Adelbert Doisy. Dam and Doisy were awarded the Nobel Prize in 1943. A dramatic story starts the discovery of dicoumarol. In the 1920s cattle in Canada began dying of internal bleeding with no obvious precipitating cause. Frank W. Schofield, a veterinary pathologist in Alberta, found that the mysterious disease was connected to the consumption of spoiled sweet clover hay and noted a prolonged clotting time. Ten years after a farmer traveled in a blizzard with his dead cow and a milk can of the unclotted blood to the University of Wisconsin. Only the door to the biochemical department of Karl Paul Link was open. This event started the isolation of the anticoagulant agent dicou- marol which was formed by microbial induced oxidation of coumarin in the mouldy sweet clover hay. More than hundred dicoumarol-like anticoagulants were synthesized by Link and his co-workers. A potent hemorrhagic agent named warfarin was first used as an effective rat poison. However, warfarin became the drug of choice and the break- through in the treatment of thromboembolic diseases. Today new oral anticoagulants are competing with warfarin.

A new dicoumarin and anticoagulant activity from Viola yedoensis Makino.

A new dicoumarin, named as dimeresculetin (1), together with another dicoumarin, euphorbetin (2) and esculetin (3) were isolated from the ethyl acetate extract of the dried whole plants of Viola yedoensis Makino. The structure of 1 was elucidated as 7-hydroxy-6-[(6,7-dihydroxy-2-oxo-2H-1-benzopyran-5-yl)oxy]-2H-1-benzopyran-2-one on the basis of extensive NMR, as well as the other spectral analysis. Compounds 1-3 exhibited anticoagulant activities with respect to activated partial thromboplastin time (APTT), prothrombin time (PT) and thrombin time (TT).

Two novel dicoumaro-p-menthanes from Gerbera piloselloides (L.) CASS.

Two new type dicoumarins (dicoumaro-p-menthanes), named dibothrioclinins I (1) and II (2) were isolated from the roots and rhizomes of Gerbera piloselloides (L.) CASS., collected in Yunnan Province, China. Their structures were elucidated on the basis of MS, 1D ((1)H-NMR, (13)C-NMR, DEPT and NOE) and 2D ((1)H-(1)H COSY, HMQC, HMBC) NMR spectral analyses. The relative structures of the two compounds were established by NOE difference spectroscopy and further confirmed by single-crystal X-ray diffraction studies.

The oral anticoagulant saga: past, present, and future.

Oral anticoagulation originated with the discovery of the harmful agent causing "sweet clover disease" in cattle in North America in the 1920s. The causative agent dicoumarol was isolated in Link's laboratory in 1940. A range of related compounds was then synthesized, the most popular of which proved to be warfarin. Oral anticoagulant administration posed problems of individual variation in response to these drugs and the need for regular laboratory monitoring by prothrombin time (PT). Monitoring problems arose from the introduction in the 1950s of some poorly responsive commercial tissue extracts for use as tissue extract thromboplastin reagent in the PT. More oral anticoagulant drug was then needed to prolong the test to the required therapeutic targets, with a resultant increase in bleeding. It was not until 1983 that the problem was resolved and it was shown that the less intense UK-type regimen was just as effective as the higher North American type dosage in the prevention of venous thrombosis but caused much less bleeding. This study led to the widespread adoption of the "low-dose warfarin" regimen that, combined with the World Health Organization PT standardization scheme using the international normalized ratio (INR), has led to improved effectiveness and safety of oral anticoagulation. This has permitted increased administration of warfarin in a widening spectrum of clinical disorders. The last remaining problem is the limited success of doctors in achieving the therapeutic INR targets, which may be improved by computer-assisted dosage.