The proteinaceous components of the gum exudates from some phyllodinous Acacia species

Acacia gum exudates are proteinaceous polysaccharides; their protein content ranges from ca 0.2 to 45%.The data presented show that the amino acid compositions of the gums from 12 phyllodinous species (10 from Bentham's sub-series Uninerves racemosae, two from sub-series Juliflorae) also vary considerably, particularly in respect of their hydroxyproline content (55 residues per 1000 residues in A. aestivalis gum, 287 residues per 1000 in A. saliciformis gum). The proportions of some other amino acids, e.g. alanine, aspartic acid, proline and serine also vary considerably, but the proportions of others, e.g. cystine, methionine, histidine, threonine, tyrosine and valine, are remarkably constant. The amino acid composition of gums with a very low protein content (e.g. A. victoriae and A. mycrobotrya) is similar to that for a highly proteinaceous gum (A. tumida). There are, however, considerable differences between the amino acid compositions of the gums from A. saligna and A. pycnantha (South African and Western Australian specimens). This strengthens previous chemotaxonomic evidence, based on the polysaccharide parameters of their gums, that these two species are not as close taxonomically as was originally believed from morphological considerations.     

The gum exudates from some closely related Acacia species of the subseries Uninerves racemosae (section phyllodineae)

Australian gum specimens from Acacia aestivalis, A. chrysella, A. jennerae and A. microbotrya (five specimens differing slightly in some morphological characters) have been studied. These species, placed within Bentham's Series 1, subseries 6F (Uninerves racemosae) are closely related, forming part of the recognized A. microbotrya group. The five specimens from A. microbotrya show minor variations, similar in extent to those established previously for gums from other species. The gums from A. chrysella and A. jennerae are similar to those from A. microbotrya in chemical composition. The gum from A. aestivalis differs from those from A. microbotrya, A. chrysella and A. jennerae in two main respects: it is more acidic and has a much higher methoxyl content. Thus significant differences in gum composition can be shown by some species that differ only slightly in morphological characters. Data for the amino acid compositions of the proteinaceous components of the gums from A. aestivalis, A. jennerae and A. microbotrya, differ considerably from those for the gums from other species belonging to the Uninerves racemosae, e.g. A. saliciformis and A. xanthina, which are much more viscous and have higher proteinaceous contents containing much higher proportions of the amino acids commonly involved in linkages with sugars. Of the closely related species studied, A. aestivalis is closer to A. microbotrya than A.jennerae in terms of the amino acid compositions of their gums, a reversal in the relative affinities shown by their polysaccharide parameters. Thus amino acid compositions are of interest chemotaxonomically and also in terms of the tertiary structures of Acacia gum exudates.     

Acacia gum exudates from species of the series gummiferae

An analytical study of the gum exudates from the African species Acacia ehrenbergiana (three specimens), A.xanthophloea (two specimens), A.hockii and A.sieberana var.villosa, and of the Australian species A.calcigera, has been made. There are now 19 species within the series Gummiferae Benth. for which gum parameters are available; of these, only A. ehrenbergiana gum displays a slightly negative optical rotation. The data for the three gum specimens from A. ehrenbergiana give a further example of the extent to which the gum from different trees of one particular species can vary in composition. The data for A.sieberana var. villosa gum are compared with the values established previously for subsp. sieberana; the differences between varieties of one species are similar in extent to those established for some subspecies. Although A. xanthophloea, A. hockii, A. ehrenbergiana, A. seyal and A. karroo are regarded as being very closely related botanically, the values for some of their analytical parameters differ considerably and strongly support the view that it is correct to retain them as distinct species.     

The amino acid composition of gum exudates from Prosopis species

The amino acid compositions of the proteinaceous components of the gum exudates from Prosopis alba, P. chilensis, P. glandulosa, P. laevigata, P. torreyana and P. velutina, and for a sample of commercial gum mesquite, are presented. In agreement with data published previously for the polysaccharide components of their gums, only minor differences in composition are shown by these species. The amino acid compositions are characterized by very high proportions of hydroxyproline and by high proportions of proline and serine; these three amino acids account for 62.5% of those present in the gum from Prosopis velutina. The amino acid compositions of these Prosopis gums are remarkably similar to that established recently for the gum from Acacia senegal (gum arabic).     

The composition of eight Acacia gum exudates from the series Gummiferae and Vulgares

An analytical study has been made of gum specimens from Acacia hebeclada, A. kirkii, A. newbrownii and A. reficiens (all of the series Gummiferae) and of Acacia erubescens, A.fleckii, A. mellifera ssp. mellifera and A. mellifera ssp. detinens (all of the series Vulgares). The data obtained give further support for the main chemotaxonomic differences between the Gummiferae and Vulgares species recorded previously. In addition, two of the species studied have exceptional features; the gum exudate from A. hebeclada contains 9.4% of nitrogen; that from A. erubescens contains 12% of glucose.     

Some highly proteinaceous Acacia gum exudates of the subseries Juliflorae

Analytical data for the gum exudates from Acacia difficilis, A. dimidiata, A. eriopoda, A. maidenii, A. stipuligera, A. torulosa and A. tumida are presented. Of these, five are highly proteinaceous; they also have high methoxyl contents and very low rhamnose contents. In contrast, A. dimidiata shows no unusual analytical parameters, and A. maidenii gum has alowarabinose content and a high rhamnose content, thus having a sugar composition of the type first observed in the gum from A. saligna. The gum from A. maidenii is also of interest as its analytical data are closely similar to those for A. longifolia, the only other tetramerous member of the subseries Juliflorae to have been studied. The data reported extend even further the unusual ranges of analytical parameters found within the Juliflorae, and confirm its great heterogeneity and chemotaxonomic interest.     

Partial structural studies of four Acacia gum exudates of the series phyllodineae

Methylation and hydrolysis studies have shown that gum specimens from Acacia difformis, A. mabellae, A. retinodes and A. rubida, which belong to Bentham's Series I (Phyllodineae), subseries 6F (Uninerves Racemosae), are similar structurally to those from A. podalyriifolia and A. pycnantha. This is further evidence that A. cyanophylla, which was placed next to A. pycnantha by Bentham, is atypical of the Series I Acacias.     

The gum exudates from some acacia subspecies of the series botryocephalae

Gum specimens from A. deanei subsp. paucijuga (two samples), A. irrorata subsp. irrorata, and A. dealbata subsp. subalpina have been analysed. There are minor differences between the two specimens from A. deanei subsp. paucijuga, but they, and the gum from A. irrorata subsp. irrorata, have analytical parameters that correspond well with those for species in the proposed Group A within the Botryocephalae. In contrast, the gum from A. dealbata subsp. subalpina conforms well with the analytical parameters established for A. dealbata gum, and the slight analytical differences lead to it being assigned with greater confidence to the proposed Group B. Now that the gum exudates from approximately 40% of the species within the Botryocephalae have been studied and shown to fall into two different types, it is hoped that the chemical data may be meaningful taxonomically.     

The composition and properties of gum exudates from subspecies of Acacia tortilis

Gum specimens from Acacia tortilis ssp. spirocarpa, ssp. raddiana var. pubescens (two specimens) and ssp. heteracantha (three specimens) have been analysed. The results are of chemotaxonomic interest. Although the gum from ssp. raddiana var. pubescens appears to be intermediate between those from ssp. spirocarpa and ssp. heteracantha in terms of some of the analytical parameters, the overall impression is that ssp. raddiana is more similar chemically to ssp. spirocarpa than to ssp. heterocantha. The latter yields a viscous, proteinaceous polysaccharide that differs from those from both ssp. spirocarpa and ssp. raddiana by having a much higher ratio of arabinose to galactose, higher nitrogen and methoxyl contents, and much higher intrinsic viscosity and molecular weight; preliminary experiments have shown this gum to consist of two components.     

The gum exudates from Brachystegia and Julbernardia species

Analytical data are presented for the water-soluble gum exudates from Brachystegia glaucescens, B. spiciformis, and Julbernardia globiflora. They are acidic polysaccharides containing glucuronic acid, 4-O-methylglucuronic acid and galacturonic acid, together with galactose, minor amounts of arabinose, and relatively high proportions of rhamnose. The exudate from B. glaucescens is of particular interest in having high molecular weight, high intrinsic viscosity, and a high methoxyl content. The nitrogen content of all three gums is low, but amino acid analysis shows that proteinaceous components are involved, as in the gum exudates from other genera.     

Acacipetalin from six species of Acacia of Mexico and Texas

Acacipetalin is the principal cyanogenic glycoside in Acacia chiapensis, A. cochliacantha, A. hindsii, A. macracantha, A. schaffneri var. schaffneri (all from Mexico) and A. schaffneri var. bravoensis (Texas).     

The composition and properties of the gum exudates from Terminalia sericea and T. Superba

The gum polysaccharides from Terminalia sericea and T. superba have been analysed. They have a complex sugar composition, containing galacturonic, glucuronic, and 4-O-methylglucuronic acids as well as galactose, arabinose, rhamnose, mannose and xylose. The exudates from T. sericea and T. superba are remarkably similar in composition, particularly with respect to their proportions of neutral sugars and total uronic acid content, although T. sericea gum contains considerably more 4-O-methylglucuronic acid than T. superba. Both gums are very viscous and dissolve readily to give solutions of good colour.!!     

Chemotaxonomic aspects of some Acacia gum exudates from series Juliflorae*

Data for the chemical composition of the gum exudates from Acacia acradenia, A. aneura, A. acuminata, A. beauverdiana, A. coolgardiensis, A. kempeana, A. microneura, A. resinomarginea, A. stereophylla and A. torulosa are presented. Comparisons with the data reported previously for other species of the series Juliflorae, viz. A. auriculiformis, A. holosericea, A. leptostachya, A. mangium and A. pubifolia confirm that the gums from this series have interesting combinations of chemical properties that are unusual in Acacia. The data do not offer much chemotaxonomic support for the groupings of the Juliflorae suggested by Bentham (1864). On the basis of their gross morphological features, the species under consideration are re-grouped in a way that is also better supported chemically.     

The population of Acacia tree species producing gum arabic in the Karamoja region, Uganda

The study aimed at determining the population status of the different Acacia tree species producing gum arabic in the undisturbed, grazed and cultivated habitats in the Karamoja region, Uganda. A total of 135 sample plots each measuring 20 × 20 m² (0.04 ha) with each habitat having 45 plots were selected and established in the seven counties using a simple random sampling technique. The tree species present, their abundances and sizes were recorded. Twelve Acacia species were identified and a total of 5535 recorded in the sampled area. Out of these, five were gum‐producing acacias. Acacia senegal dominated the acacias in all the seven counties and in all habitats of Karamoja with Acacia nilotica (72.3%), Acacia seyal (13.4%), Acacia sieberiana (4%) and Acacia gerrardii (2.6%). Non‐gum‐producing acacias constituted 7.19% of the total abundance. The tree densities increased with increase in tree size in the undisturbed and grazed habitats but decreased in the cultivated habitat. Most Acacia trees were of large size, an indication of old age and poor regeneration that could affect their future population status. It is recommended that further investigations be carried out into the causes of poor regeneration of Acacia species.     

Chaetosphaeria tortuosa, the newly discovered teleomorph of Menispora tortuosa, with a key to known Menispora species

Chaetosphaeria tortuosa is described as the newly discovered teleomorph of Menispora tortuosa, based on specimens from Canada and the Czech Republic, and single spore isolations from both morphs. The fungus produces superficial, more or less globose, papillate, dark brown to black smooth perithecia (200–)220–250 × (220–)230–260 μm. The asci are unitunicate, 8-spored, cylindrical-fusiform, (110–)120–133(–145) × 12–14 with a distinct apical, nonamyloid annulus 1–1.5 μm high, 3.5–4 μm wide. The ascospores are fusiform, 19–24 × 5–6 μm, hyaline, 3-septate, smooth, and 2-seriate in the ascus. The morphology of the teleomorph and anamorph are similar to that of C. ovoidea (anamorph: M. glauca), differing in dimensions of asci and ascospores, and in the disposition and morphology of the phialides of the anamorphs. The generic concept and phylogeny of Menispora is briefly discussed, and a key to the 11 species currently accepted in the genus is provided.     

Free amino acids in the seeds of Acacia species

Free amino acids in the seeds of 80 species of Acacia have been determined. In addition to confirming the known difference in seed amino acid ‘patterns’ shown by species of the series Gummiferae on the one hand and species of the series Phyllodineae and Botryocephalae on the other, we have found that species of the series Vulgares Benth. show two additional ‘patterns’. One of these is common to some of the Afro-Asian species of the series which have been analysed and the other is common to species from America and Africa. One of the ‘marker’ amino acids of the Afro-Asian group is the neurotoxic lathyrogen α-amino-β-oxalylaminopropionic acid. The possible taxonomic and phylogenetic significance of these results is discussed, with special reference to five species A. albida, A. confusa, A. heterophylla, A. coulteri and A. kauaiensis.     

Structural studies of gum arabic, the exudate polysaccharide from Acacia senegal

A 25.182-MHz ¹³C-n.m.r. spectrum of gum arabic allows unambiguous characterisation of all the C-1 resonances. These assignments have been confirmed by correlation of the modification of the intensities of these signals after controlled acid hydrolysis and characterisation of the released fragments. The resonances of the other carbons have been assigned through partial relaxed T₁ spectra of the polysaccharides obtained by graded degradation of the gum. These results indicate gum arabic to consist mainly of a (1→3)-β- -galactan core with (1→6)-β- -galacto-pyranosyl branches and with - -arabinofuranosyl-(1→3)-- -arabinofuranosyl and - -rhamnopyranosyl-(1→4)-β- -glucopyranosyluronic acid groups attached to positions 3 and 6, respectively, of the branch units.     

Structure of the exudate gum from Meryta sinclairii

A gum that exudes from the wounded trunk of the New Zealand native tree Meryta sinclairii has been isolated. The gum was completely precipitated by the β-glucosyl Yariv reagent and was thus determined to be an arabinogalactan-protein (AGP). It contained >95% w/w carbohydrate and only 2% w/w protein with a high level of hydroxyproline. SEC-MALLS showed that the gum had a weight-average molecular weight of 4.45×10⁶ Da compared with 6.02×10⁵ Da for gum arabic. Constituent sugar and linkage analyses were consistent with polymers comprised of a highly branched backbone of 1,3-linked galactopyranosyl (Galp) residues, with side-chains made up of arabinofuranose- (Araf) containing oligosaccharides, terminated variously by rhamnopyranosyl (Rhap), arabinopyranosyl (Arap), Galp and glucuronopyranosyl (GlcpA) residues. Analysis by one-dimensional and two-dimensional ¹H and ¹³C NMR experiments confirmed the linkage analyses. The structure of the gum is discussed in comparison with the structure of gum arabic and other AGPs.     

A survey of alkaloids in the genera Harpalyce and Brongniartia (Fabaceae—Brongniartieae)

The presence of alkaloids in six species of Brongniartia and three species of Harpalyce is reported. This survey revealed remarkable qualitative differences in the alkaloid profiles of these two genera. B. discolor, B. lupinoides, B. sousae and B. intermedia showed a typical -pyridone pattern, with cytisine, anagyrine and baptifoline as major alkaloids. In leaves of the first three species ormosanine-type alkaloids occurred additionally. B. flava and B. vazquezii are devoid of -pyridones, but accumulate lupanine, hydroxylated lupanines and ester alkaloids. All three species of Harpalyce were similar in accumulating -pyridones, but H. formosa differed from H. brasiliana and H. pringlei in the presence of epilupinine. In general the alkaloid profiles of Brongniartia and Harpalyce show similarities to those of the Australian genera Hovea, Lamprolobium, Plagiocarpus and Templetonia and support therefore the actual concept of the enlarged tribe Brongniartieae.