The effects of dietary gum karaya (Sterculia) in man.

Following a 7-day control period, 5 male volunteers consumed 10.5 g gum karaya (GK) daily for 21 days. Measurements before and at the end of the test period showed that the ingestion of GK had no significant effect on the following: intestinal transit time, faecal wet or dry weight, concentrations of faecal fat, total and individual volatile fatty acids, bile acids, and neutral sterols; breath hydrogen and methane concentrations; glucose tolerance; serum cholesterol, HDL cholesterol, triglycerides and phospholipids; plasma biochemistry; haematological indices; urinalysis parameters. The daily test intake, which was large in relation to the very minor amounts of GK used in foodstuffs, did not cause any toxic effects in terms of the wide range of measurements made; moreover the GK had no metabolic action of any consequence.

Subchronic toxicity study in rats fed gum karaya.

Gum karaya was given to groups of 15 rats of each sex at levels of 0 (control), 0.2, 1 or 5% (w/w) in the diet for 13 wk. An increase in faecal bulk was seen in all treated groups throughout the study. There was a decrease in weight-gain at the highest dietary level (significant only in the females), which was associated with a marginal reduction in food-conversion efficiency. Males given 1 or 5% drank more than the controls and a transient increase in water intake was seen in females given the highest level. The no-untoward-effect level from this study was 5% (w/w) of the diet, providing a mean intake of about 4 g karaya gum/kg body weight/day.

Immunogenicity, immunological cross reactivity and non-specific irritant properties of the exudate gums, arabic, karaya and tragacanth.

An animal model has been used to investigate the immunogenicity and non-specific irritant properties of exudate gums. The materials studied were four preparations of gum arabic (Acacia spp.), two of gum karaya (Sterculia spp.), two of gum tragacanth (Astralagus spp.) and a residue obtained after ethanol extraction of gum arabic. Groups of animals were intradermally immunized with the gum in complete Freund's adjuvant. Serum antibody levels were measured by an ELISA technique and delayed hypersensitivity responses by a footpad swelling test. Antigenic cross-reactivity within each gum species was tested in a crossover fashion. All gum preparations elicited systemic immune responses after immunization. Further processing reduced immunogenicity, although there was no evidence that systemic immunity to these complex polysaccharide antigens responses could be completely abolished by processing or purification. The ethanolic extract, and some of the gum preparations, particularly tragacanth and karaya, caused considerable footpad swelling when injected intradermally. It is concluded that processing and awareness of subspecies differences can reduce the inherent immunogenicity and potential irritant effects of exudate gums.