Characterization and Toxicological Study of Combretum glutinosum Gum

Abstract

Twenty samples of Combretum glutinosum gum were collected from Blue Nile state in Sudan during the seasons 2007 and 2008. Different physicochemical methods were used to characterize these gums. A representative composite sample for season 2007 and composite sample for season 2008 was used to evaluate the toxicity of Combretum glutinosum gum. Parameters such as moisture content, ash content, pH value, nitrogen and protein content, acid equivalent weight and total uronic acid, intrinsic viscosity, tannin and starch and dextrin content were determined. Results obtained show no significant differences within samples. The mean values obtained for the properties studied are as follows: moisture content 7.96%, ash content 4.51%, pH 4.5, nitrogen content 0.37%, protein content 2.43%, acid equivalent weight 1524.15, total uronic acid 15.53%, intrinsic viscosity 11.2 ml g-1, tannin and starch or dextrin were not detected in Combretum glutinosum gum. Solubility of Combretum glutinosum gum showed that it had low solubility in water (30%), but it dissolved perfectly in basic media where solubility reached 96.3% in Na2Co3, 40% in EDTA. Acid hydrolysis of Combretum glutinosum gum followed by HPLC measurements revealed it’s sugars content, arabinose 56.1%, galactose 33% and rhamnose 10.9%. Cationic composition studied using Atomic Absorption technique showed that Calcium, potassium and magnesium are the most abundant elements present with the mean values in (p.p.m) are 46.73, 35.97 and 17.36 respectively. Iron, cobalt, nickel, cadmium, lead, copper, zinc, chromium and aluminum (in p.p.m) have mean values of 0.55, 0.065, 0.07, 0.2, 0.163, 0.015, 0.06, 2.07and 1.272 respectively. This indicates that the Combretum glutinosum gum is a salt of calcium, magnesium, and potassium. FTIR spectra of Combretum glutinosum samples showed the presence of hydroxyl, carbonyl, alkanes, alkenes and Phenols as functional groups. The number average molecular weight of Combretum glutinosum gum determined from osmotic pressure was 1.8×10 4 Dalton. Toxicological study using in vitro cytotoxic methods involving Combretum glutinosum gum on different types of normal and cancer human cell lines was undertaken to assess the safety of using the gum as food additive. The results showed that Combretum glutinosum gum differed in toxicity profile from gum arabic. The mean values of IC50 on normal human cell line; were found to be 108.25 µg/ml using baby hamster normal kidney fibroblast cell line (BHK), while it required doses higher than 500 µg ml-1 on normal melanocytes cell line (HFB4). The mean IC50 values on the two cancer cell lines; were found to be 51.75 µg ml-1 on human hepatocellular carcinoma cell line (HEPG2) and 44.5 µg ml-1 on human colon carcinoma cell line (HCT116). Prediction of LD50 starting doses was estimated from the values of IC50 using Halle’s RC prediction model and was calculated and found to be in the range 0.03-0.02 g/Kg body weight on both normal and cancer cell lines respectively.