Abstract
Many of the health benefits associated with Aloe species have been attributed to the polysaccharides contained in the gel of the leaves. The aim of this study was to investigate the chemical composition as well as the biological evaluation of polysaccharides isolated from the leaves of eight different Aloe species, A. vera (A1), A. arborescens (A2), A. eru (A3), A. grandidentata (A4), A. perfoliata (A5), A. brevifolia (A6), A. saponaria (A7) and A. ferox (A8) grown in El Orman Botanical Garden, Giza, Egypt. Polysaccharides from the plants were isolated using hot extraction method and then hydrolyzed. The polysaccharide hydrolysates were identified using high performance liquid chromatographic technique. Maximum yield of total polysaccharides identified were obtained from A7 (12.04%), A1 (8.51%), A8 (8.03%), A2 (5.32%) and A6 (2.18%) respectively. The isolated polysaccharides were tested for antihyperglycemic activity in alloxan-induced diabetic rats and alpha glucosidase inhibitory activity. Chromatographic investigation of the polysaccharides recorded the presence of 18 saccharides, glucuronic acid, stachyose, galacturonic acid, sucrose, glucose, xylose, galactose, rhamnose, mannose, arabinose, fructose polyol, mannitol and sorbitol in the eight Aloe species, but their quantitative composition differed among the species. Glucuronic acid, stachyose and galacturonic acid were the major detected saccharides. The results of the biological activities revealed significant antihyperglycemic activities with variable degrees. After four weeks of daily administration, polysaccharides isolated from A. vera (A1) and A. arborescens (A2) were the most active with 40 and 44% reduction in blood glucose level, respectively. All the tested polysaccharides showed significant alpha glucosidase inhibitory activity with IC50 (µg/ml) 11.70, 14.60 and 15.80 for A7, A6 and A1 respectively. In conclusion, the tested polysaccharides contribute to the antidiabetic action of these Aloe species. Key words: Aloe, alpha glucosidase inhibitors, antidiabetic, polysaccharide.
Highlights
Diabetes is a chronic metabolic disorder characterized by high blood glucose levels (American Diabetes Association, 2009)
A. barbadensis Miller may contain 2.5 times the aloe-emodin of A. ferox Miller; the time of harvest may a factor into the composition variation
Diab., diabetic, the mucilage samples were injected at a dose of 250 mg kg-1 body weight; Glucuronic acid, Stachyose, Galacturonic acid and mixture were injected at a dose of 50 mg kg-1 body weight; metformin is injected at a dose 100 mg kg-1 body weight; (n=6). * Significantly different from zero time at p
Summary
Diabetes is a chronic metabolic disorder characterized by high blood glucose levels (American Diabetes Association, 2009). In type-2 diabetes, there is a gradual development of insulin resistance and beta cell dysfunction, strongly associated with obesity and a sedentary lifestyle (Zimmet et al, 2001). In the Middle East and North Africa Region, 1 in 10 adults have diabetes (Klautzer et al, 2014); the region has the highest prevalence of diabetes (10.9%). The International Diabetes Federation (IDF) estimated that there are 34.6 million people with diabetes in the Middle East and North Africa, a number that will almost double to 67.9 million by 2035 if concerted action is not taken to tackle the risk factors fuelling the epidemic of diabetes throughout the region (IDF, 2013). Egypt is ranked eighth highest in the world in terms of the disease (IDF, 2013)
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