Leurocristine from Catharanthus roseus

Until separation techniques such as chromatography (28,29) and counter-current extraction had advanced sufficientiy to be of widespread use, the principal alkaloids were isolated from plant extracts and the minor constituents were either discarded or remained uninvestigated. With the advent of, first, column, then preparative thin layer, and now high pressure Hquid chromatography, even very low concentrations of materials of physiological significance can be obtained in commercial quantities. The alkaloid leurocristine (vincristine, 22, R = CHO), one of the more than 90 alkaloids found in Catharanthus roseus G. Don, from which it is isolated and then used in chemotherapy, occurs in concentrations of about 2 mg/100 kg of plant material. 

A number of alkaloids with the aspidospermine skeleton occur in the genus Vinca and are dealt with in detail in Chapter 12. They include the very important base vindoline (CIII) which not only occurs as the free base in Vinca rosea (= Lochnera rosea = Catharanthus roseus) but also as part of the dimeric alkaloids vinblastine (vincaleucoblastine) and leurosine, whereas the Aa-formyl analog, CIV, forms part of the dimeric alkaloid leurocristine (5, 72a). These dimeric alkaloids have been used successfully for the treatment of certain forms of cancer in man (5). Vindolinine (CVI) has also been isolated from V. rosea and its dihydro-decarbomethoxy derivative, tuboxenin (CVI-A), which is the parent member of the series, occurs in a Pleiocarpa species (53). ( + )-Vincadif-formine (XCIII, 6, 74) has already been mentioned as the racemic form of (— )-6,7-dihydrotabersonine (Section II, O). It has been found in V. difformis and in Rhazya stricta (51b) where the (+) form also occurs. 

In 1959 a series of bisindole alkaloids were isolated from Vinca rosea L. Catharanthus roseus G. Don). Of signal importance have been vinblastine (169) (= vincaleukoblastine) and vincristine (170) (= leurocristine), both of which show anti-tumour activity (see Section 18, p. 333). Structurally clarified also are leurosidine (= vinrosidine), leurosine, pleurosine, and isoleurosine , while only one half of Catharine is known. 

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