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Anthocyanins of the genus Erythrina (Fabaceae)
BiochemicalSystematicsand Ecology,Vol. 19, No. 4, pp. 329-332, 1991. Printed in GreatBritain.
0305-1978/91 $3.00+0.00 © 1991 PergamonPressplc.
Anthocyanins of the Genus Erythrina (Fabaceae) RON SCOGIN Rancho Santa Ana Botanic Garden, Claremont, CA 91711, U.S.A.
Key Word Index--Ery~dTrina; Fabaceae; anthocyanins; pollination ecology; chemotaxonomy. Abstract--Floral anthocyanins of 21 species of Erythrina consist of glucosides of pelargonidin and cyanidin. No correlation between floral pigments and either taxonomy or class of avian pollinator could be detected.
Introduction The genus Erythrina comprises 108 currently recognized species [1 ], representatives of which occur on all continents except Europe and Antarctica. Selected aspects of the genus Erythr/na have been intensively studied and the results of these studies have been presented in several recent symposia on the biology of this genus [2-5]. Phytochemical aspects of Erythrina which have been examined include seed amino acids [6], alkaloids [7], and nectar constituents [8]. Comparative studies of the phenolic chemistry of Erythrina species have been notably lacking. The phenolic constituents of selected species have been examined, usually species of pharmacological interest by virtue of their use in folk medicine. Woody tissues (roots and bark) have been most commonly examined. The most frequently reported flavonoids have been isoflavonoids [e.g. 9] and their derivatives, pterocarpans [e.g. 10]. Reports of flavanones and chalcones have also been published [e.g. 10]. Materials and Methods Plantrnaterials. Fresh floral material was collected from plants in cultivation at the Huntington Botanic Garden and the Los Angeles State and County Arboretum. Anthocyanin identification. Extraction, purification and identification by paper chromatography in four solvents (BAW, Bu-HCI, 15% HOAc, 1% HCI) were performed according to the standard procedures of Harborne
[11]. Results and Discussion
Floral anthocyanin pigments identified from 21 Erythrina species and two cultivated, interspecific hybrids are presented in Table 1. Also included in Table 1 are reports from the literature of floral pigments in five additional species.
Aglycones Pelargonidin and cyanidin glucosides co-occur as floral pigments in 16 of the 21 Erythrina species examined. Two species exhibit only cyanidin glucosides (E. pudica, E. herbacea) and three species produce only pelargonidin glucosides (E. guatemalensis, E. humeana, E. acanthocarpa). In addition, E. subumbrans was reported by Lowry [12] to produce only cyanidin 3-sophoroside and E. poeppigiana was reported by Forsyth and Simmonds [13] to produce only pelargonidin glucosides. No delphinidin glycosides were detected in the present study, although Verma et al. [14] reported delphinidin 3,5-diglucoside from E. suberosa. Both the occurrence of delphinidin and the reported glucosylation pattern are unique among studies of Erythrina species reported to date. A confirmation of the pigments of E. suberosa and a study of the three additional species of section Suberosae would be of great interest. (Received 10 January 1991) 329
330
R. SCOGIN
TABLE 1. FLORAL ANTHOCYANINS OF THE GENUS ERYTHRINA. PIGMENTS ARE PRESENTED iN ORDER OF DECREASING AMOUNT AND MINOR CONSTITUENTS ARE INDICATED BY PARENTHESES Section
Species
Pigments*
E. cn~ta-gal/i¢~ L. E. crista-galli E. crista-galli§ E. falcata¢- Bentham E. falcata§ E.poeppigiana (Walpers) O. F. Cook E. domingueziit Hassler
Cs, Cg, Pg Cs, Cg, Pg [20] Pg, Cs [21] Ps, Cs, Pg Ps, Pg, Cg [21] Pg, Ps [13] Ps, Cs, Pg, Cg [21 ]
Humeanae (1/2) Acanthocarpae (1/1 )
E. suberosa$ Roxburgh E. subumbrans$ (Hasskarl) Merrill E. speciosa Andrews E. atitlanensis Kruckoff & Barneby E. berteroana Urban E. chiapasana Krukoff E. coralloides D.C. E. flabelliformis Kearney E. folkersiiKrukoff & Moldenke E. guatemalenst~ Krukoff E. herbacea L. E. macrophylla D.C. E. mexicana Krukoff E. pudica Krukoff & Barneby E. tajumulcensis Krukoff & Barneby E. corallodendrum L. E. cora/Iodendrum§ E. pal/ida Britton & Rose E. caffra$ Thunberg E. lysistemon$ Hutchinson E. humeana$ Sprengel E. acanthocarpa'~ E. Meyer
P35g, C35g, D35g, [14] Cs, [12] Ps, Cs, (Pg) Ps, Pg, Cs Ps, Pg, (Cs) Cs, Ps, Pg Pg, Cg, (Ps) Ps, Cs, Pg Ps, Pg, (Cs) Ps, (Pg) Cs, Cg Ps, Pg, (Cs) Ps, Cs, Pg Cg, Cs Ps, Pg, (Cs) Ps, Cs, Pg Cs, Cg [20] Pg, Cs [13] Ps, Pg, (Cs) Ps, Cs, Pg Ps, (Pg) Ps, Pg
Subgenus Chirocalyx Chiroca/yx (1/14)
E. abyssl#~#a$ Lamarck
Ps, Cs, Pg
Subgenus Erythraster Erythraster (1/2)
E. van~gata$ L.
Ps, Cs [12]
E. x bidw~7/i E. x sykesii
Cs, Ps, (Cg) Ps, Pg, Cs
Subgenus Micropteryx Cn~tae-ga/fi (2/2)t
Micropteryx (2/4)
Subgenus Erythrina Suberosae (1/4) Hypaphorus (1/1 ) Stenotropfs (1/1 ) Erythrina (12/35)
Corallodendra (2/10)
Caffrae (2/2)
Named interspecific hybrids
*Cs=cyanidin 3-sophoroside, Cg=cyanidin 3-glucoside, Ps = pelargonidin 3-sophoroside, Pg= pelargonidin 3-glucoside, D35g = delphinidin 3,5-diglucoside, C35g = cyanidin 3,5-diglucoside, P35g = pelargonidin 3,5-diglucoside; t(a/b): a = species examined in the present study, b = number of species in the section; :~Passerine pollinated; §Conflicting report.
Although both pelargonidin and cyanidin glucosides co-occur in most Erythrina species, pelargonidin glucosides are the major pigments in 17 of the 21 species examined in the present study. The only exception to this pattern are E. chiapasana in which pelargonidin 3-sophoroside is codominant with cyanidin 3-sophoroside and E. crista-galliin which pelargonidin 3-glucoside is a minor constituent relative to cyanidin glucosides.
Glucosylation pattern All anthocyanidin pigments detected in the present study were glucosylated at the 3 position only, and only two sugar moieties, glucose and sophorose, were found. Glucose and sophorose substitutions co-occur (often on different aglycones) in all 21 of the species examined in the present study. Sophorose is the major sugar
ANTHOCYANINS OF ERYTHRINA
331
substituent in almost every species. Among pelargonidin-containing species, sophorose is the dominant sugar moiety in 17 of 18 species (excepting only E. corralIoides) and among cyanidin-containing species sophorose is dominant in 16 of 18 cases (excepting only E. coralloides and E. pudica). Erythrina coralloides is unique in producing glucose as the sugar substituent on both major constituents.
Pigments and pollinators All species of Erythrina are currently thought to be pollinated principally by birds [15, 16]. Old World species are pollinated by perching, passerine birds of several families and New World species are mostly hummingbird-pollinated. Hummingbird pollination is regarded as a derived condition and about a dozen New World species retain the ancestral pollination by non-specialized passerines [5]. Some phytochemical features, such as nectar sugar composition, are strongly correlated with the class (hovering or perching) of avian pollinator [17]. The occurrence in Erythrina of sucrose-richness of nectar sugars among hummingbird-pollinated species and of hexose-richness of nectar sugars among passerine-pollinated species was confirmed by Baker and Baker [8]. In contrast to nectar chemistry, floral pigmentation in Erythrina does not appear to be correlated with avian pollinator type. Among the four species producing primarily or solely cyanidin glucosides, two are hummingbird-pollinated (E. herbacea and E. pudica) and two are passerine-pollinated (E. cristagalli and E. subumbrans). Similarly, among the four species producing solely pelargonidin glucosides, two are passerine-pollinated (E. acanthocarpa and E. humeana) and two are hummingbird-pollinated (E. guatemalensis and E. poeppigiana). Among the remaining 19 species (which exhibit pelargonidin dominated floral pigments), six are passerine-pollinated and 13 are hummingbird-pollinated. These results are in contrast with those reported by Scogin [18] in a larger survey of anthocyanidins of bird-visited flowers. The results of that survey revealed that, on a global basis, cyanidin glycosides are most frequent among passerine-visited flowers and pelargonidin glycosides are most frequent among hummingbird-visited flowers. While there does not appear to be a clear correlation between pigment aglycone and avian pollinator class, the possiblity remains that the floral colors (as perceived by flower visitors) resulting from anthocyanin pigmentation may be correlated with pollinator class. This possibility is under investigation.
Pigments and taxonomy No clear correlation between pigment distribution and taxonomy is apparent. Within each taxonomic section for which pigment data are available from two or more species, different combinations of the four anthocyanins occur among member species of the section. These results suggest that diversification with respect to pigment biosynthesis occurred very early in the evolutionary history of the genus Erythrina (perhaps even in its evolutionary antecedent) and prior to taxonomic and geographic radiation within the genus.
Geography No patterns of pigment distribution emerge from a comparison of four continental areas in which Erythrina occurs (North America, South America, Australasia and Africa). Species of North and South America have the complete complement of various combinations of the four pigments (and also the most complete sampling of species). Species from Africa which have been examined lack cyanidin-3-glucoside. The geographic origin of Erythrina is uncertain, but either Africa or South America have been suggested [2, 16]. The occurrence of a primitive pigment character state (cyanidin 3-glucoside present [19]) among South American species could support, albeit weakly, Neill's [16] suggestion of an origin of Erythrina on that continent. It would
332
R. SCOGIN
appear likely that full floral pigment diversification occurred in early representatives of Erythrina and prior to dispersal from its place of origin to other continents. The only detectable correlation between geography and floral pigments is the dominance of pelargonidin glucosides in African, especially South African, species. South African species produce only traces of (E. caffra) or no detectable cyanidin glucosides (E. humeana, E. acanthocarpa). Tropical African species (E. lysistemon, E. abyssinica) produce cyanidin 3-sophoroside as a minor constituent. Of particular interest in this connection would be knowledge of the floral pigments of E. zeyher~ the second species of subgenus Erythrina section Humenae of South Africa. If it produces only pelargonidin glucosides, as does E. humanea (the other section member), then floral pigments would exhibit both a taxonomic and further geographic correlation.
Literature report inconsistencies Some inconsistencies exist among literature reports and the present results with respect to Erythrina anthocyanins. The species for which inconsistent reports exist are indicated in Table 1. These inconsistencies may arise from intraspecific variation in floral pigment constitution. Acknowledgements--I gratefully acknowledge the generous cooperation of the staff of the Huntington Botanic Garden and the Los Angeles State and County Arboretum.
References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21.
Krukoff, B. A. and Barneby, R. C. (1974) Lloydia 37, 332. Raven, P. H. (1974) Lloydia 37, 321. Raven, P. H. (1977) Lloydia 40, 401. Raven, P. H. (1979) Ann. MissouriBot. Gdn 66, 417. Barneby, R. C., Krukoff, B. A. and Raven, P. H. (1982) Allertonia 3, 1. Romeo, J. J. and Bell, E. A. (1974) L~oydia 37, 543. Jackson, A. H., Ludgate, P., Mavraganis, V. and Redha, F. (1982) Allertonia 3, 47. Baker, I. and Baker, H. G. (1982) Allertonia 3, 25. Fomum, Z. T., Ayasor, J. F. and Wandji, J. (1985) Phytochemistry25, 3075. Kamat, V. S., Chuo, F. Y., Kubo, I. and Nakanishi, K. (1981) HeterocyclesS, 1163. Harborne, J. B. (1963) Comparative Biochemistry of the Flavonoids. Academic Press, London. Lowry, J. B. (1972) Malaysian J. Sci. 1A, 133. Forsyth, W. G. C. and Simmonds, N. W. (1954) Proc, Roy. Soc. Lond. 1428, 549. Verma, Y. S., Saxena, V. K. and Nigam, S. S. (1977) Proc. Natn. Acad. Sc~, India 47A, 71. Hernandez, H. M. and Toledo, V. M. (1982) Allertonia 3, 77. Neill, D. A. (1988) Ann. MissouriBot. Gdn75, 888. Baker, H. G. and Baker, I. (1983) in Handbook of Experimental Pollination Biology (Jones, C. E. and Little, R. J., eds), p. 117. Van Nostrand Reinhold, New York. Scogin, R. (1989) Bot. Gaz. 149, 437. Harborne, J. B. (1977) Biochem. Syst. Ecol. 5, 7. Shibata, M and Yoshitama, K. (1969) Bot. Mag. (Tokyo) 82, 139. Pomilio, A. B., Sproviero, J. F. and Fernandez, M. E. (1971) An. Assoc. Quire. Argent. 59, 29.
0305-1978/91 $3.00+0.00 © 1991 PergamonPressplc.
Anthocyanins of the Genus Erythrina (Fabaceae) RON SCOGIN Rancho Santa Ana Botanic Garden, Claremont, CA 91711, U.S.A.
Key Word Index--Ery~dTrina; Fabaceae; anthocyanins; pollination ecology; chemotaxonomy. Abstract--Floral anthocyanins of 21 species of Erythrina consist of glucosides of pelargonidin and cyanidin. No correlation between floral pigments and either taxonomy or class of avian pollinator could be detected.
Introduction The genus Erythrina comprises 108 currently recognized species [1 ], representatives of which occur on all continents except Europe and Antarctica. Selected aspects of the genus Erythr/na have been intensively studied and the results of these studies have been presented in several recent symposia on the biology of this genus [2-5]. Phytochemical aspects of Erythrina which have been examined include seed amino acids [6], alkaloids [7], and nectar constituents [8]. Comparative studies of the phenolic chemistry of Erythrina species have been notably lacking. The phenolic constituents of selected species have been examined, usually species of pharmacological interest by virtue of their use in folk medicine. Woody tissues (roots and bark) have been most commonly examined. The most frequently reported flavonoids have been isoflavonoids [e.g. 9] and their derivatives, pterocarpans [e.g. 10]. Reports of flavanones and chalcones have also been published [e.g. 10]. Materials and Methods Plantrnaterials. Fresh floral material was collected from plants in cultivation at the Huntington Botanic Garden and the Los Angeles State and County Arboretum. Anthocyanin identification. Extraction, purification and identification by paper chromatography in four solvents (BAW, Bu-HCI, 15% HOAc, 1% HCI) were performed according to the standard procedures of Harborne
[11]. Results and Discussion
Floral anthocyanin pigments identified from 21 Erythrina species and two cultivated, interspecific hybrids are presented in Table 1. Also included in Table 1 are reports from the literature of floral pigments in five additional species.
Aglycones Pelargonidin and cyanidin glucosides co-occur as floral pigments in 16 of the 21 Erythrina species examined. Two species exhibit only cyanidin glucosides (E. pudica, E. herbacea) and three species produce only pelargonidin glucosides (E. guatemalensis, E. humeana, E. acanthocarpa). In addition, E. subumbrans was reported by Lowry [12] to produce only cyanidin 3-sophoroside and E. poeppigiana was reported by Forsyth and Simmonds [13] to produce only pelargonidin glucosides. No delphinidin glycosides were detected in the present study, although Verma et al. [14] reported delphinidin 3,5-diglucoside from E. suberosa. Both the occurrence of delphinidin and the reported glucosylation pattern are unique among studies of Erythrina species reported to date. A confirmation of the pigments of E. suberosa and a study of the three additional species of section Suberosae would be of great interest. (Received 10 January 1991) 329
330
R. SCOGIN
TABLE 1. FLORAL ANTHOCYANINS OF THE GENUS ERYTHRINA. PIGMENTS ARE PRESENTED iN ORDER OF DECREASING AMOUNT AND MINOR CONSTITUENTS ARE INDICATED BY PARENTHESES Section
Species
Pigments*
E. cn~ta-gal/i¢~ L. E. crista-galli E. crista-galli§ E. falcata¢- Bentham E. falcata§ E.poeppigiana (Walpers) O. F. Cook E. domingueziit Hassler
Cs, Cg, Pg Cs, Cg, Pg [20] Pg, Cs [21] Ps, Cs, Pg Ps, Pg, Cg [21] Pg, Ps [13] Ps, Cs, Pg, Cg [21 ]
Humeanae (1/2) Acanthocarpae (1/1 )
E. suberosa$ Roxburgh E. subumbrans$ (Hasskarl) Merrill E. speciosa Andrews E. atitlanensis Kruckoff & Barneby E. berteroana Urban E. chiapasana Krukoff E. coralloides D.C. E. flabelliformis Kearney E. folkersiiKrukoff & Moldenke E. guatemalenst~ Krukoff E. herbacea L. E. macrophylla D.C. E. mexicana Krukoff E. pudica Krukoff & Barneby E. tajumulcensis Krukoff & Barneby E. corallodendrum L. E. cora/Iodendrum§ E. pal/ida Britton & Rose E. caffra$ Thunberg E. lysistemon$ Hutchinson E. humeana$ Sprengel E. acanthocarpa'~ E. Meyer
P35g, C35g, D35g, [14] Cs, [12] Ps, Cs, (Pg) Ps, Pg, Cs Ps, Pg, (Cs) Cs, Ps, Pg Pg, Cg, (Ps) Ps, Cs, Pg Ps, Pg, (Cs) Ps, (Pg) Cs, Cg Ps, Pg, (Cs) Ps, Cs, Pg Cg, Cs Ps, Pg, (Cs) Ps, Cs, Pg Cs, Cg [20] Pg, Cs [13] Ps, Pg, (Cs) Ps, Cs, Pg Ps, (Pg) Ps, Pg
Subgenus Chirocalyx Chiroca/yx (1/14)
E. abyssl#~#a$ Lamarck
Ps, Cs, Pg
Subgenus Erythraster Erythraster (1/2)
E. van~gata$ L.
Ps, Cs [12]
E. x bidw~7/i E. x sykesii
Cs, Ps, (Cg) Ps, Pg, Cs
Subgenus Micropteryx Cn~tae-ga/fi (2/2)t
Micropteryx (2/4)
Subgenus Erythrina Suberosae (1/4) Hypaphorus (1/1 ) Stenotropfs (1/1 ) Erythrina (12/35)
Corallodendra (2/10)
Caffrae (2/2)
Named interspecific hybrids
*Cs=cyanidin 3-sophoroside, Cg=cyanidin 3-glucoside, Ps = pelargonidin 3-sophoroside, Pg= pelargonidin 3-glucoside, D35g = delphinidin 3,5-diglucoside, C35g = cyanidin 3,5-diglucoside, P35g = pelargonidin 3,5-diglucoside; t(a/b): a = species examined in the present study, b = number of species in the section; :~Passerine pollinated; §Conflicting report.
Although both pelargonidin and cyanidin glucosides co-occur in most Erythrina species, pelargonidin glucosides are the major pigments in 17 of the 21 species examined in the present study. The only exception to this pattern are E. chiapasana in which pelargonidin 3-sophoroside is codominant with cyanidin 3-sophoroside and E. crista-galliin which pelargonidin 3-glucoside is a minor constituent relative to cyanidin glucosides.
Glucosylation pattern All anthocyanidin pigments detected in the present study were glucosylated at the 3 position only, and only two sugar moieties, glucose and sophorose, were found. Glucose and sophorose substitutions co-occur (often on different aglycones) in all 21 of the species examined in the present study. Sophorose is the major sugar
ANTHOCYANINS OF ERYTHRINA
331
substituent in almost every species. Among pelargonidin-containing species, sophorose is the dominant sugar moiety in 17 of 18 species (excepting only E. corralIoides) and among cyanidin-containing species sophorose is dominant in 16 of 18 cases (excepting only E. coralloides and E. pudica). Erythrina coralloides is unique in producing glucose as the sugar substituent on both major constituents.
Pigments and pollinators All species of Erythrina are currently thought to be pollinated principally by birds [15, 16]. Old World species are pollinated by perching, passerine birds of several families and New World species are mostly hummingbird-pollinated. Hummingbird pollination is regarded as a derived condition and about a dozen New World species retain the ancestral pollination by non-specialized passerines [5]. Some phytochemical features, such as nectar sugar composition, are strongly correlated with the class (hovering or perching) of avian pollinator [17]. The occurrence in Erythrina of sucrose-richness of nectar sugars among hummingbird-pollinated species and of hexose-richness of nectar sugars among passerine-pollinated species was confirmed by Baker and Baker [8]. In contrast to nectar chemistry, floral pigmentation in Erythrina does not appear to be correlated with avian pollinator type. Among the four species producing primarily or solely cyanidin glucosides, two are hummingbird-pollinated (E. herbacea and E. pudica) and two are passerine-pollinated (E. cristagalli and E. subumbrans). Similarly, among the four species producing solely pelargonidin glucosides, two are passerine-pollinated (E. acanthocarpa and E. humeana) and two are hummingbird-pollinated (E. guatemalensis and E. poeppigiana). Among the remaining 19 species (which exhibit pelargonidin dominated floral pigments), six are passerine-pollinated and 13 are hummingbird-pollinated. These results are in contrast with those reported by Scogin [18] in a larger survey of anthocyanidins of bird-visited flowers. The results of that survey revealed that, on a global basis, cyanidin glycosides are most frequent among passerine-visited flowers and pelargonidin glycosides are most frequent among hummingbird-visited flowers. While there does not appear to be a clear correlation between pigment aglycone and avian pollinator class, the possiblity remains that the floral colors (as perceived by flower visitors) resulting from anthocyanin pigmentation may be correlated with pollinator class. This possibility is under investigation.
Pigments and taxonomy No clear correlation between pigment distribution and taxonomy is apparent. Within each taxonomic section for which pigment data are available from two or more species, different combinations of the four anthocyanins occur among member species of the section. These results suggest that diversification with respect to pigment biosynthesis occurred very early in the evolutionary history of the genus Erythrina (perhaps even in its evolutionary antecedent) and prior to taxonomic and geographic radiation within the genus.
Geography No patterns of pigment distribution emerge from a comparison of four continental areas in which Erythrina occurs (North America, South America, Australasia and Africa). Species of North and South America have the complete complement of various combinations of the four pigments (and also the most complete sampling of species). Species from Africa which have been examined lack cyanidin-3-glucoside. The geographic origin of Erythrina is uncertain, but either Africa or South America have been suggested [2, 16]. The occurrence of a primitive pigment character state (cyanidin 3-glucoside present [19]) among South American species could support, albeit weakly, Neill's [16] suggestion of an origin of Erythrina on that continent. It would
332
R. SCOGIN
appear likely that full floral pigment diversification occurred in early representatives of Erythrina and prior to dispersal from its place of origin to other continents. The only detectable correlation between geography and floral pigments is the dominance of pelargonidin glucosides in African, especially South African, species. South African species produce only traces of (E. caffra) or no detectable cyanidin glucosides (E. humeana, E. acanthocarpa). Tropical African species (E. lysistemon, E. abyssinica) produce cyanidin 3-sophoroside as a minor constituent. Of particular interest in this connection would be knowledge of the floral pigments of E. zeyher~ the second species of subgenus Erythrina section Humenae of South Africa. If it produces only pelargonidin glucosides, as does E. humanea (the other section member), then floral pigments would exhibit both a taxonomic and further geographic correlation.
Literature report inconsistencies Some inconsistencies exist among literature reports and the present results with respect to Erythrina anthocyanins. The species for which inconsistent reports exist are indicated in Table 1. These inconsistencies may arise from intraspecific variation in floral pigment constitution. Acknowledgements--I gratefully acknowledge the generous cooperation of the staff of the Huntington Botanic Garden and the Los Angeles State and County Arboretum.
References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21.
Krukoff, B. A. and Barneby, R. C. (1974) Lloydia 37, 332. Raven, P. H. (1974) Lloydia 37, 321. Raven, P. H. (1977) Lloydia 40, 401. Raven, P. H. (1979) Ann. MissouriBot. Gdn 66, 417. Barneby, R. C., Krukoff, B. A. and Raven, P. H. (1982) Allertonia 3, 1. Romeo, J. J. and Bell, E. A. (1974) L~oydia 37, 543. Jackson, A. H., Ludgate, P., Mavraganis, V. and Redha, F. (1982) Allertonia 3, 47. Baker, I. and Baker, H. G. (1982) Allertonia 3, 25. Fomum, Z. T., Ayasor, J. F. and Wandji, J. (1985) Phytochemistry25, 3075. Kamat, V. S., Chuo, F. Y., Kubo, I. and Nakanishi, K. (1981) HeterocyclesS, 1163. Harborne, J. B. (1963) Comparative Biochemistry of the Flavonoids. Academic Press, London. Lowry, J. B. (1972) Malaysian J. Sci. 1A, 133. Forsyth, W. G. C. and Simmonds, N. W. (1954) Proc, Roy. Soc. Lond. 1428, 549. Verma, Y. S., Saxena, V. K. and Nigam, S. S. (1977) Proc. Natn. Acad. Sc~, India 47A, 71. Hernandez, H. M. and Toledo, V. M. (1982) Allertonia 3, 77. Neill, D. A. (1988) Ann. MissouriBot. Gdn75, 888. Baker, H. G. and Baker, I. (1983) in Handbook of Experimental Pollination Biology (Jones, C. E. and Little, R. J., eds), p. 117. Van Nostrand Reinhold, New York. Scogin, R. (1989) Bot. Gaz. 149, 437. Harborne, J. B. (1977) Biochem. Syst. Ecol. 5, 7. Shibata, M and Yoshitama, K. (1969) Bot. Mag. (Tokyo) 82, 139. Pomilio, A. B., Sproviero, J. F. and Fernandez, M. E. (1971) An. Assoc. Quire. Argent. 59, 29.