CLASSIFICATION OF NATURAL GUMS .7. RELATIONSHIPS BETWEEN THE SERIES VULGARES (ACACIA-SENEGAL) AND GUMMIFERAE (ACACIA SEYAL)

Principal component analysis, cluster analysis and discriminant component analysis have been used to study the relationship between the two series of Acacia gums Gummiferae Benth (= subgen Acacia Vas.) and Vulgares Benth (= subgen Aculeiferum Vas.). The main commercial gums within these series A. senegal and A. seyal were scrutinized individually and the Acacia gums, in turn compared with another chemically related, but not species related, Combretum gums. On the basis of %N and composition of 18 amino acids A. seyal falls within the A. senegal cluster. Combretum gums are quite distinctive from the Acacia gums. Analysis by covariance further confirms that despite the lower %N in A. seyal compared to A. senegal this alone is insufficient to distinguish between them based on amino acid composition. On this basis A. seyal and A. senegal are 'closely related'. When nine analytical parameters associated with the carbohydrate moiety are evaluated, members of the Gummiferae series are found to form a greatly extended cluster in keeping with their wider taxonomic origin and development. Although the Vulgares series members fall into a more compact cluster, there are individual members at the regions of overlap between the two Series more 'closely related' to members of the Gummiferae series than to A. senegal, which like A. seyal fall into a compact cluster. Therefore, despite their taxonomic identification as separate species, there are chemical and corporate similarities between A. senegal and A. seyal which signal caution in selecting specific parameters to distinguish between them when setting up a regulatory specification. The results indicate that overall there are greater similarities between A. senegal and A. seyal than there are differences between them.