Vinblastine from catharanthine

Fig. (2). Biosynthesis of vinblastine from the monomeric precursors catharanthine and vindoline. Anhydrovinblastine is the direct product of the dimerization reaction and the precursor of the anticancer drugs. Shaded areas indicate the structural differences between the precursor catharanthine and the deavamine part of...

In literature very little is published on the extraction of alkaloids on an industrial scale. The few papers available were published between 1950 and 1970 and concern the isolation of alkaloids from whole plants or plant parts 168,169). The extraction of catharanthine and vinblastine from C. roseus leaves on a pilot plant scale is described by Atta-ur-Rahman et al. (170). Svoboda developed a method for the extraction of ajmalicine, vinblastine, and vincristine which has been used by Eli Lilly Co. (169,171-173). Supercritical fluid extraction is a method which is used for the extraction of caffeine from coffee beans. This method also seems of interest for further studies of other alkaloids. 

A highly efficient and commercially important synthesis of vinblastine from catharanthine and vindoline has recently been described (48). 

As shown in Scheme 13.57, consummation of the synthesis of (+)-vinblastine required activation of the catharanthine fragment (from Scheme 13.56) and reaction of that activated piece with the (-)-vindoline fragment from Scheme 13.53. Then, once the two fragments had been cojoined, the final protecting groups were removed, and the last ring was put in place. 

Ionic liquid-based ultrasound-assisted extraction (ILUAE) was successfully applied to the extraction of three alkaloids, vindoline, catharanthine, and vinblastine from Catharanthus roseus. Twelve ionic liquids, with different cations and anions were investigated in this work. In addition, ultrasound extraction parameters, including soak time, solid-liquid ratio, ultrasound power and time, and the number of extraction cycles, were optimized. ILUAE offered short extraction times (from 0.5 to 4 h) and remarkable efficiency. Therefore, the use of ionic hquids in the ultrasound-assisted extraction of key chemicals from medicinal plants shows great potential [12]. 

Yang L, Wang H, Zu Y, Zhao C, Zhang L, Chen X, Zhang Z (2011) Ultrasound-assisted extraction of the three terpenoid indole alkaloids vindoline, catharanthine and vinblastine from Catharanthus roseus using ionic liquid aqueous solutions. Chem Eng J 172 705-712... 

Extensive biotransformation studies have been conducted with the As-pidosperma alkaloid vindoline, but much less work has been done with monomeric Iboga and dimeric alkaloids from this plant. The long-standing interest in this group of compounds stems from the clinical importance of the dimeric alkaloids vincristine and vinblastine, both of which have been used for more than 2 decades in the treatment of cancer. Few mammalian metabolites of dimeric Catharanthus alkaloids have been characterized. Thus the potential role of alkaloid metabolism in mechanism of action or dose-limiting toxicities remains unknown. The fact that little information existed about the metabolic fate of representative Aspidosperma and Iboga alkaloids and Vinca dimers prompted detailed microbial, mammalian enzymatic, and chemical studies with such compounds as vindoline, cleavamine, catharanthine, and their derivatives. Patterns of metabolism observed with the monomeric alkaloids would be expected to occur with the dimeric compounds. 

Goodbody and co-workers (7/9) have examined the production of alkaloids in root and shoot cultures induced from seedlings of C. roseus. The pattern of alkaloids in the root cultures was similar to that of the roots from intact plants. Thus ajmalicine (39) and catharanthine (4) were produced, but no vindoline (3), a major leaf alkaloid, and no bisindole alkaloids. Similarly, the pattern of the alkaloid content of the shoot cultures was like that of the leaves of the intact plant, showing the presence of vindoline (3), catharanthine (4), and ajmalicine (39), with 3 predominating. A search for the bisindole alkaloids in the cultures indicated the presence of anhydrovinblastine (8) and leurosine (11) in the shoot cultures (2.6 and 0.3 xg/g fresh weight, respectively), but no vinblastine (1) or vincristine (2). 

Continued work by the same group 123) has led to the first isolation of vinblastine (1) from a multiple shoot culture of C. roseus. The most productive line, MSC-B-1, consisted of two distinctly different tissues, multiple shoots and unorganized tissue, and was maintained growing and productive for 30 months. Vinblastine (1) was isolated by HPLC, and the content was estimated to be 15 jjig/g dry weight. Production of this alkaloid was greater than that in the callus culture but less than that observed for the parent plant, even though the levels of catharanthine (4) and vindoline (3) were about the same. 

The enzyme-catalyzed formation of anhydrovinblastine (8) from catharanthine (4) and vindoline (3) was first examined by Kutney and co-workers (170,219) using a cell-free preparation. [ao f- H]Catharanthine (4) and [acety/- C]vindoline (3) were incubated for 3-8 hr, both separately and jointly with a preparation from C. roseus, which led to the isolation of labeled anhydrovinblastine (8) and leurosine (11) incorporations were of the order of 0.54 and 0.36%, respectively. On this basis, anhydrovinblastine (8) was proposed as the key biosynthetic intermediate en route to vinblastine (1) and vincristine (2). 

The conversion of anhydrovinblastine (8) to vinblastine (1) has been examined by several different groups, using intact plants, cell suspension systems, and cell-free preparations. From the studies discussed above it was clear that 3, 4 -anhydrovinblastine (8) was probably the initially formed intermediate in the condensation of vindoline (3) and catharanthine (4) prior to vinblastine (1). Kutney and co-workers have reported (225,226) on the biotransformation of 3, 4 -anhydrovinblastine (8) using cell suspension cultures of the 916 cell line from C. roseus a line which did not produce the normal spectrum of indole alkaloids. After 24 hr the major alkaloid products were leurosine (11) and Catharine (10) in 31 and 9% yields, respectively, with about 40% of the starting alkaloid consumed. 

The extremely low yield of vincristine (2) from intact plants has made pursuit of its biosynthesis a very challenging problem, which at this point in time remains unsolved. Kutney et al. have used both anhydrovinblastine (8) (227) and catharanthine N-oxide (107) (233) as precursors to vincristine (2) in a cell-free preparation, but incorporation levels were extremely low. Therefore, the question of whether vinblastine (1) is an in vivo, as well as an in vitro, precursor remains to be answered. Several possibilities exist for the overall oxidation of vinblastine (1) to vincristine (2), including a direct oxidation of the A-methyl group or oxidative loss of the N-methyl group followed by N-formylation. 

Vinblastine is a highly effective anticancer agent currently used clinically against leukemia, Hodgkin s lymphoma, and other cancers. (113, 114). Vinblastine is derived from dimerization of vindoline and another terpenoid indole alkaloid, catharanthine. 

If the C-15, C-16 bond is oxidatively cleaved, the secodine skeleton results (the proposed progenitor of the Aspidosperma and the iboga systems) through alternative Diels-Alder type cyclizations to afford tabersonine and catharanthine. The bisindole alkaloids of Catharanthus roseus reflect the union of vindoline and catharanthine to afford anhydrovinblastine modification affords the clinically significant alkaloids, vinblastine (VLB) and vincristine (VCR Fig. 39). The alkaloids, particularly VCR, are important as anticancer agents and have led to the development of the semisynthetic derivatives vindesine and vinorelbine (Fig. 40). Synthetic approaches are available to join the monomeric precursors. The enzymatically controlled sequence of reactions from tabersonine to vindoline has been elucidated. 

This reaction has been extensively studied in the case of the chlopromazine radical (R -mediated aminopyrine (S) oxidation [41], a typical reaction for xenobiotics, as well as in the case of the vindoline radical (R -mediated catharanthine (S) oxidation [42], a key reaction in the biosynthesis of the anticancer drugs, vinblastine and vincristine, which are obtained from Catharanthus roseus. 

Catharanthine (LIV) and vindoline (Lin) are regarded as the monomeric precursors of the dimeric alkaloids vinblastine and vincristine, via a-3 ,4 -anhydrovinblastine. C. roseus peroxidase catalyzes the coupling reaction of catharanthine and vindoline (Scheme XXVI) to lead to a-3 ,4 -anhydrovinblastine (XLVH) or, more properly, to an iminium intermediate (LVI) from which a-3 ,4 -anhydrovinblastine is directly derivated [52,74,166]. a-3 ,4 -Anhydrovinblastine is then converted to vinblastine (XLIX, R = CH3) and vincristine (XLIX, R = CHO) in C. roseus plants [167-169], a-3 ,4 -Anhydrovinblastine (XLVn), or the unstable iminium intermediate (LVI) formed during the coupling reaction, is then assumed to be the precursor of all dimeric alkaloids in C. roseus. 

VInorelbine Tartrate. Vinorcibine tartrate. Navelbinc. is a new scmisynthctic vinca alkaloid derived from vinblastine by loss of one carbon from ring C and dehydration in ring D. both in the catharanthine moiety. It is named 3. 4 -didehydro-4 -dcoxy-C -norvincalcukoblastinc. Navcibine is supplied in vials containing 10 mg/mL of solution in a volume of I mL of Water for Injection or 10 mg/mL of solution in a volume of 5 mL of Water for Injection. Unopened vials are stable at room temperature fur up to 72 hours. It is diluted to a concentration of 0.5 In 2 mg/mL with 0.9% Sodium Chloride Injection or 5% Dextrose Injection for intravenous infusion or slow intravenous push administration. 

The partial synthesis of vinblastine itself makes use of 20-acetoxycatharanthine (223), prepared from catharanthine as described earlier. The modified Polonovski reaction in the presence of vindoline gave an intermediate immonium ion, which was reduced to 20 -acetylvinblastine (Scheme 37). Mild alkaline hydrolysis afforded deacetylvinblastine, the secondary hydroxy-group of which could be re-acetylated preferentially, with formation of vinblastine (271). ... 

The monomers catharanthine and vindoline, which form the dimer, occur in much higher concentration, and it has been possible to synthesise the dimeric vinblastine (sterically correct) from the two monomers. 

In 1975, Potier and collaborators proposed that, in planta, the dimeric vinblastine type alkaloids resulted from the coupling of catharanthine and vindoline and, in light of this hypothesis, they reported for the first time the chemical synthesis of a dimer with the natural configuration through a modified Polonovski reaction [18, 19]. This reaction resulted in the formation of an iminium dimer which, after reduction with NaBH4, yielded a-3 ,4 -anhydrovinblastine, Fig. (2), later proved to be the first dimeric biosynthetic precursor of vinblastine in the plant. The group of Potier investigated possible modifications of anhydrovinblastine and produced vinorelbine, Fig. (1), which was the first active derivative with an altered cleavamine (catharanthine) moiety [20, 21]. 

In face of the structural similarities unraveled during the 1960s of vindoline and catharanthine with the dimeric alkaloids, and due to their great abundance in the plant, these two compounds were immediately considered the most likely monomeric precursors of the Vinca alkaloids, although the cleavamine moiety of vinblastine presented some differences from catharanthine, namely a fragmentation of the C5-C18 bond, Fig. (2). 

The chemical coupling of catharanthine and vindoline to yield anhydrovinblastine led to the obvious hypothesis that this compound might also be the first product of dimerization in the plant, and the dimeric precursor of vinblastine and vincristine. For three years it was not possible to find anhydrovinblastine in the plant, until Scott et al. in 1978 [115], by modifying the established methods for extraction and purification of alkaloids, isolated anhydrovinblastine from C. roseus plants, with incorporation of radiolabelled catharanthine and vindoline, thus proving that anhydrovinblastine was actually a natural product. 

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