Biochem/calSystematicsandEcology, Vol. 9, No. 4, pp. 267-273, 1981. 0305-1978/81/040267-07 $02.00/0 Printed in Great Britain. © 1981 Pergamon Press Ltd.

Quinolizidine Alkaloids as Systematic Markers of the Genisteae*

ANTONIO SALATINO and OTTO R. GOTTLIEB Institute de Biociencias and Instituto de Quimica, Universidade de S~o Paulo, Brazil

Key Word Index - Papilionoideae; Genisteae; quinolizidine alkaloids; biochemical evolution; biochemical systematics.

Abstract - A previously reported postulate concerning the evolution of quinolizidine alkaloids and the detailed consideration of the chemical composition led to a revised dendrogram showing proposed phylogenetic relations within the subfamily Papilionoideae in general and the tribe Genisteae in particular.

IntreduelJon According to Bernasconi et aL [2] two lines of descent for sections of the genus Genista (Leguminosae-Papilionoideae), one based on Genistoides and one on Spartioides, both endowed with incipient adaptation to drought and with high proportions of pyridone bases (cytisine, anagyrine), develop into other sections, such as Ephedrospartum and Astero- spartum as well as into the genus Retama, which are highly xerophytic and possess high propor- tions of sparteine bases (sparteine, retamine). In a recent paper [3] we expressed the view that specialization in pyridones is an advanced character, and conseouently considered Retama to be more primitive than Genista.

Another problem concerns the location of the genus Cydsus. Both Bernasconi et al. [2] and ourselves [3] placed Cytisus close to Genista. While the former authors distinguish these genera by the alleged absence of retamine in Cyt/sus, we juxtapose the genera on account of the reported presence of this alkaloid also in Cydsus [4, 5]. In opposition, morphological classifications hold Cydsus far from Genista near Sarothamnus [6], which is sometimes even sunk into synonymy with Cytisus [7, 8].

Based on the distribution of alkaloids reported up to the end of 1979, and on the ecogeography of the Genisteae genera, we aim, by the clarifi- cation of these problems, to improve our proposed phylogenetic relations of quinolizidine-bearing Papilionoideae [3].

*Part XIX in the series "Chemosystematics and Phylogeny". For Part XV(II, see ref. [1].

Results and discussion An affinity diagram for genera of the Papilionoideae [3] was based inclusively on a unified biogenetic scheme for the formation of quinolizidine skeletons, presented in a modified form (see below) in Fig. 1, and on an updated version of Mears and Mabry's [9] review of quino- lizidine data. These authors mention sparteine as the alkaloid of Genista ephedroides, G. falcata, G. flor/da, G. hirsuta, G. sylvestris and G. tejedensis while the article by Bernasconi eta/. [10] quoted as reference demonstrates the additional presence of anagyrine, cytisine, lupanine, N- methylcytisine and retamine in these species. In their review, furthermore, Mears and Mabry follow Hutchinson [7] in sinking Retama into synonymy with Genista. From the point of view of micromolecular systematics, however, it is advisable to maintain the genera as separate entities, since all matrine alkaloids so far reported in Genista s./. were isolated from Retama (R. monosperma, R. raetam, R. rhodorhizoides).

In an accordingly revised version of the affinity diagram (Fig. 2) Retama, with more highly oxidized and more widely distributed-alkaloid types, is registered at a less advanced position than Genista. The Cadia group of the Sophoreae contains still more highly oxidized and more widely distributed quinolizidine types (see Fig. 2) and, indeed, morphological evidence also testifies for its primitiveness [8]. Quinolizidine-containing Cad/a species occur in tropical Africa, as do Retama species which reach from the Sahara to the Iberian peninsula [3, 10]. This genus producing tetrahydroanabasine, matrine,

(Received 14 November 1980; received forpublicatlon 9 April 1981 )

"267

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sparteine and cytisine alkaloids, albeit in simple forms, displays a chemical versatility well suited for a taxon destined to give rise to several more specialized lines. Significantly, cytisine is not a reliable marker for Retarna. Although cytisine, N- methylcytisine or both were reported to exist in three species [11-13], Bernasconi et al. were not able to reproduce the results [10]. In contrast to

Retama, Genista species cover a much more northern area, extending from the north of Africa to Siberia (with G. tinctoria and G. sib/rica).

In Genista s.s. synthesis of matrine alkaloids is suppressed possibly in view of an enhanced productivity of cytisine derivitives, an evidence which distinguishes the genus from Sophoreae. The highest efficiency of cytisine production

QUINOLIZIDINE ALKALOIDS AS SYSTEMATIC MARKERS OF THE GENISTEAE 269

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characterizes Gen/stoides, precisely the section whose species occur at the greatest distance from tropical Africa. While, as thus suggested, evolution from a chemically Retama-like ancestor led to a group of Genisteae (group 2) even richer in cytisine, it was already suggested in our previous paper [3] that evolution from a chemically Virgi/ia- like ancestor led to group 1 of Genisteae (Argyro- Iobium, Lupinus, Sarothamnus) fundamentally only through diversification of oxygenation patterns.

The postulate that evolution was accompanied by the gradual substitution of retamine by cytisine suggests the evolutionary relationships among sections of species as expressed in Fig. 3. In this dendrogram the line (sections Scorpioides, Echino- spartum, Erinacoides, Spartoides) characterized

by ( + )- or ( - )-sparteine, as well as by a relatively feeble proportion of retamine as opposed to a high proportion of pre-cytisine-type alkaloids, is associated with two other lines. One of these lines is formed by a group of sections (Astero- spartum, Ephedrospartum, Voglera, Phyl/o- spartum, Genistella, Chamaespartum) charac- terized by (-)-sparteine as well as by a rela- tively high proportion of retamine as opposed to a low proportion of pre-cytisine-type alkaloids. The other line is formed by Genistoides and the Thermopsideae relatively rich in cytisine-type alkaloids. Cytisine production attains its maximum in the genera Petteria, Spartium, U/ex and Laburnum. In consistence with this point of view, species of Genistoides are ecogeographi- cally associated with Thermops/s of north Asia

270 ANTONIO SALATINO AND OTTO R GOTTLIEB

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(through e.g. Genista sibirica with a high cytisine content) as well as with Petteria of the Balkans (through e.g. Gen/sta/ydia).

As a climactic development, pyrrolizidine alka- loids appear, in addition to quinolizidine alkaloids, in Laburnum and Adenocarpus and in exclusion to other alkaloid types in Crotalaria.

Let us return at this point to Retarna or a chemically similar north African ancestor possessing all four quinolizidine characters expressed in biosynthetically simple forms. Should now alternatively production of matrine

alkaloids be enhanced at the expense of sparteine alkaloids, genera endowed with the composition of the sophoreous group comprising Amrnothamnus, Keyser/ingia, Goebelia and Sophora would be expected to arise. Indeed Arnrnothamnus, the most specialized genus in matrine chemistry, is also the most advanced from the distributional point of view (Fig. 4). The alternate derivation from Ormosia-like ancestors is not likely either on chemical grounds: Orrnosia alkaloids are derived sparteine types (cf. also Fig. 1), or on geographical grounds: Orrnosia is

QUINOLIZIDINE ALKALOIDS AS SYSTEMATIC MARKERS OF THE GENISTEAE 271

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FIG. 4. GEOGRAPHIC DISTRIBUTION OF GENISTA AND PAFffLIONOIDEAE G E ~ A BEARING MATRINE-TYPE QUINOLIZI- DINE ALKALOIDS.[~7~ ] Retama, [~-~] Genista, [ r"-~t Goebelia, ~ Keysorlingla, ~ ] Ammotharnnus. Another genus (not indicated) is Sophora.

concentrated towards the far south-east Asian end of the line of dispersal of quinolizidine- bearing Papilionoideae.

The observed alternation of sparteine and matrine chemistries seems to indicate their close biosynthetic relationship. Both alkaloid types may either stem from an identical precursor [14] or from alternative precursors [15], unless one acknowledges the possibility that alkaloids of the sparteine group can rearrange into alkaloids of the matrine group [16]. With respect to this last hypothesis it is attractive to consider that the sparteine-type alkaloid retamine is functionalized at C-7, precisely the position which contributes to the crucial C-7/C-11 bond formation in the matrine type. Either of these alternatives would require the insertion of the matrine sequence at or near the sparteine sequence as shown in Fig. 1, placing the fundamental structure of lamprolobine (11.3) (to which it was connected previously [3, 14]) at the end of a biosynthetic pathway. Indeed, compounds of this type have never been observed to co-occur with matrine

alkaloids, and the sole reported representative does not even occur in Sophoreae but only in Lupinus (Genisteae) [17] and in Lamprolobium, a chemically little-known genus but which is certainly derived, belonging to the Australian tribe Bossiaeeae.

The dendrogram (Fig. 5) expressing chemo- geographical affinities of quinolizidine-bearing Papilionoideae [18], and which induced these comments on the biological replacement of retamine by matrine, contains an additional modi- fication with repect to the original version [3]. Cytisus is now included in group 1 of Genisteae. Its previous placement in group 2 was based on reports concerning the presence of retamine in C. purgans [4] and C. fontanesii Spach [5]. The latter species, however, has also been designated Genista biflora DC., a binomial preferred by Steinegger and Herdt [5], in view of the chemical composition. Thus, among the analysed Cytisus species only one yielded retamine and more than 50% are devoid of pyridone alkaloids. As seen above this is an atypical situation for Genista, where retamine and cytisine are both very common. Pointing in the same direction, 13- hydroxylupanine-derived alkaloids are widespread in Cytisus and occur but rarely in Genista. They are, however, common also in Sarothamnus and Lupinus. The latter genus is also noted for the development of the singular oxygenation patterns of aphylline and 7-hydroxysparteine as well as monspessulanine which, albeit sporadically, also appear in constituents from Cytisus; as well as for oxygenation at C-17 of the sparteine skeleton which occurs in addition only in Cytisus. Considering chemical affinities Cytisus is thus better accommodated near Argyrolobium, Lupinus and Sarothamnus.

References 1. Ferreira, Z. S. and Gottleib, O. R. Biochem. Syst. Ecol.

(in press). 2. Bernasconi, V., Gill, St. and Steinegger, E. (1965) Pharm.

Acta Helv. #8, 275. 3. Salatino, A. and Gottlieb, O. R. (1980) Biochem. Syst.

Ecol. 8, 133. 4. Adzet, T., Battlori, L. and San Martin, R. (1970) Plant

Med. Phytother. 4, 21. 5. Steinegger, E. and Herdt, E. (1968) Pharm. Acta Helv.

5°443. 6. Schulze-Menz, G. K. (1964) in Engler's Syllabus der

Pflanzenfamilien (Melchior, H., ed.) 12th edn, Vol. 2, p. 230. Gebrueder Borntraeger, Berlin.

7. Hutchinson, J. (1964) The Genera of Flowering Plants, Vol. 1, p. 297. Clarendon Press, Oxford.

272 A N I - O N t O S A L A ] I N O A N D O T f O R GOTTLIEB

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QUINOLIZIDINE ALKALOIDS AS SYSTEMATIC MARKERS OF THE GENISTEAE 273

8. PoHI, R. (1981) in Advances in Legume Systematics (Polhill, R. M. and Raven, P. H., eds.), p. 191. Royal Botanic Gardens, Kew.

9. Mears, J. A. and Mabry, T. J. (1971)in Chemotaxonomy of the Leguminosae (Harborne, J. B., Boulter, D. and Turner, B. L., eds.) p. 73. Academic Press, New York. Bernasconi, R., Gill, St. and Steinegger, E. (1965) Pharm. Acta Helv. 40, 246. Ahmed, Z. F. and Rizk, A. (1963) J. Chem. U. A. R. 6, 227; (1965)Chem. Abstr. 6,3, 3312. Ahmed, Z. F., Rizk, A. M. and Hammouda, F. M. (1972) Postep Dziedzinine Leku Ros/., Pr. ReL Dosw. Wygloszone Symp. 1970; (1973) Chem. Abstr. 78,94856.

10.

11.

12.

13. Rodrigues, F., Gonzalez, A. and Mendez, A. (1966). An. Rep. Soc. Esp. Fis. Qufm. B. 62, 853; (1967) Chem. Abstr. 68, 73210.

14. Geissman, T. A. and Crout, D. H. G. (1969) Organic Chemistry of Secondary Plant Metabolism, p. 451. Freeman, Cooper, San Francisco.

15. Golebiewski, W. M. and Spenser, I. D. (1976) J. Am. Chem. Soc. 98, 6726.

16. Kushmuradov, Yu. K., Aslanov, Kh. A., Schuette, H. R. and Kuchkarov, S. (1977) Khim. Pn7. Soedin. 244; (1977) Chem. Abstr. 87, 98901.

17. Keller, W. J. (1980) Phytochemistry19, 2233. 18. Salatino, A. and Gottleib, O. R. (1981) Rev. Bras. Bot.

(in press).