Protoberberine alkaloids producers

Three syntheses of 6,7-secoberbines have been carried out. Two of them involved degradation of the protoberberine alkaloids (63,65), and the third was a total synthesis (69). Takao and Iwasa (63) applied the von Braun reaction to tetrahydrocoptisine (39) to obtain the 6,7-seco bromide 63, which on treatment with dimethylamine, followed by hydrolysis, gave tetrahydro-corydamine (64). This tetrahydrobase 64, which was also produced from 56 by zinc in hydrochloric acid (63), was dehydrogenated to corydamine (56) (Scheme 15). 

Administration of triply, 3C-labelled (5)-reticuline to a stable variant non-alkaloid producing cell culture line of Thalictrum tuberosum in cell culture demonstrated a very high incorporation of label into protoberberine alkaloids that were subsequently produced. Since this cell line does not produce reticuline, because the cell line lacks or has insufficient quantities of three methyltransferases that lead to the formation of reticuline, cell cultures that contain this cell line are appropriate for the study of biosynthetic studies., 3C NMR spectroscopy and CIMS were utilized to follow the time course of the metabolism, and demonstrated the rapid formation of scoulerine as a primary reaction product, followed by further tetrahydroprotoberberines and dehydroprotoberberines. The apparently reversible formation of dehydroscoulerine in significant amounts was interpreted as evidence for the role of this compound as an alkaloidal storage product from which scoulerine may be regenerated via enzymic reduction. Scoulerine, dehydroscoulerine, columbamine, and (S)-reticuline were detected by l3C NMR in the crude extracts, while berberine was detected by HPLC. The biosynthetic pathway of these protoberberines in this variant cell culture were summarized as follows [151] (S)-reticuline > scoulerine -> tetrahydrocolumbamine (hypothetical) -> columbamine -> dehydroscoulerine -> candadine -> berberine. 

Berberis cell cultures were also reported to produce bisbenzylisoquino-line alkaloids. Cassels et al. 412) screened 34 callus cell lines (33 species). In all cases the protoberberine alkaloid Jatrorrhizine was the major component in aU but 12 cell lines bisbenzylisoquinoline alkaloids were found. High levels of berbamine were found in B. angulosa (0.8% of dry weight) and B. henryana (0.48%). Berbamunine (16) and the new alkaloid 2-norberbamunine (17) were the major alkaloids in B. stolonifera cell lines... 

Figure 2. Families reported as producers of protoberberine alkaloids.

Only one plant in this family was cited as producing protoberberine alkaloids, Alstonia macrophylla (12), 5delding the alkaloid berberine. 

Surprisingly, from a family known for producing many different kinds of alkaloids, only one species was reported in the literature as producing protoberberine alkaloids. From Aniba canelilla seven different protoberberines were isolated (5). 

This is by far the richest family in terms of protoberberine alkaloids. 123 species from 18 different genera were studied and produced 54 different alkaloids in 332 citations (45% of the total number of citations of this type of alkaloid in the period covered by this review). The genus Corydalis has the largest number of citations, with a total of 121 from 38 species, followed by Papaver with 95 from 29 species, and Fumaria with 35 citations from 17 species. Corydalis is the second richest single genus in terms of citations regarding protoberberine alkaloids. 

Following the previous reviews published by Manske (1954), Jeffs (1967), and Bhakuni (1986), it is easy to see that the research on these alkaloids has grown substantially. This review covers the period from 1986 to 2001, and it shows that there were 589 citations describing studies on the phytochemistry and/or biological activities of 138 protoberberine alkaloids isolated from 310 plants from 13 families. Among the families cited as producers of protoberberine alkaloids, a simple analysis of Fig. 1, calls attention to the vast majority of citations from plants of the family Papaveraceae with 332 citations (45% of the total), followed by the family Berberidaceae with 144 citations (19%), and the family Ranunculaceae with 90 citations (12%). In terms of the number of different protoberberine alkaloids isolated from the families, again the family Papaveraceae comes in first place with 54 different alkaloids (39%), followed by the family Menispermaceae with 42 (30%), and the family Annonaceae with 36 (26%) different alkaloids. Chart 1 also shows that the families Apocynaceae, Fabaceae, Polygalaceae, and Rubiaceae each had only one alkaloid of this type described in the period. 

The selection procedure for these cultures producing protoberberine alkaloids is easy due to their yellow colour and their fluorescence in UV light. In the case of other benzylisoquinoline alkaloids, like the morphinans for example, immunological methods, especially the radioimmunoassay (Hodges and Rapoport 1982, Hsu et al. 1983, Wieczorek et al. unpublished) are useful for testing large numbers of small colonies (clones) to find possible ceU lines with increased production of these alkaloids. 

Three of the alkaloids (55-57) were isolated from Corydalis incisa (63-65) and two (57, 58) from Hypecoum procumbens (66), where they coexist with the parent protoberberines. They are formed in plants by an oxidative C-6—N bond cleavage, possibly through an aldehyde intermediate 61. This assumption was supported by in vivo experiments in which ( )-tetrahydrocorysamine-8,/4-/2 (59) and (+ )-tetrahydrocoptisine-8,74-/2 (60) were fed to Corydalis incisa (67) to produce corydalic acid methyl ester-8-/ (55) along with corydamine-8-f (58) and corydalic acid methyl ester-8-/ (55) with corynoline-8-/ (62), a benzophenantridine alkaloid, respectively (Scheme 14). 

A number of plants produce laticifers filled with latex. For example, isoquinoline alkaloids in the family Papaveraceae are abundant in the latex (59), where they are sequestered in many small latex vesicles. In latex vesicles of Chelidonium majus the concentration of protoberberine and... 

Besides yielding a wealth of alkaloids belonging to the benzyliso-quinoline, bisbenzylisoquinoline, and protoberberine series, Thalictrum fendleri C. L. Anders also produces the new alkaloid thaliporphine (XXIV), C20H23O4N (mp 170°-172°) (43). 

The enamide photocyclization reaction has been widely exploited for the synthesis of protoberberine and other alkaloids (see Vol. 4 of these Reports and ref. 7). It has now been found that enamides of the type (160 X = OMe) undergo photochemical elimination of methanol to produce in good yield protoberberine precursorsofthetype(161). Forexample,compounds(161 R = R = H, = OMe),2 2 (151. r4 H r2 1 3 OCHjO), and (161 ... 

Meconopsis comprises some 40 species which are mainly indigenous to China and the Himalayas. Protopine (3), protoberberine (5), benzophenanthridine (6), isopavine (13) and aporphine alkaloids (Fig. 2) have been isolated from a small number of species. Rhoeadine alkaloids, which are present in Papaver species, also occur in Meconopsis and their distribution appears to be limited to these two genera (Slavik and Slavikova 1977). The sole European representative, M. cambrica growing in England produces magnoflorine (4) as the major alkaloid, together with protoberberine (5), proaporphine (14) and promorphinan alkaloids (15) (Hemingway et al. 1981). 

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