Helen N. Asemota

Genetic variation and cultivar identification of Jamaican yam germplasm by random amplified polymorphic DNA analysis

SummaryWe have used random amplified polymorphic DNA (RAPD) analysis to characterize eleven cultivars of the five economically most important yam species grown in Jamaica (Dioscorea alata, D. cayenensis, D. rotundata, D. trifida and D. esculenta). Amplification of genomic DNA samples with nine different arbitrary 10mer primers revealed a total of 338 different band positions, ranging in size from 0.3 to 2.5 kb. RAPD patterns proved to be highly reproducible and somatically stable. While no variation was observed among plants belonging to the same cultivar, a large number of intervarietal and interspecific polymorphisms enabled us to reliably discriminate between all Jamaican cultivars investigated.

Plasma and liver lipid distributions in streptozotocin-induced diabetic rats fed sapogenin extract of the Jamaican bitter yam (Dioscorea polygonoides)

Abstract Bitter yam ( Dioscorea polygonoides ) steroidal sapogenin extract and commercial diosgenin were administered to diabetic rats for 21 days. Plasma glucose and lipids were assessed. Liver lipid distributions were also determined. The two dietary supplements fed to diabetic rats resulted in significant decreased body weight gain. The test diets significantly lowered plasma glucose and total cholesterol. Sapogenin extract supplement significantly lowered plasma total triglycerides. Plasma and liver VLDL+LDL-cholesterol were significantly reduced while the HDL fraction was increased in diabetic rats fed the test supplements. These results showed that the consumption of the two supplements maybe useful in the management of hypercholesterolemia often associated with diabetes.

Citrus peel polymethoxylated flavones extract modulates liver and heart function parameters in diet induced hypercholesterolemic rats

The primary aim of this study was to investigate the effects of Ortanique peel polymethoxylated flavones extract (PMF(ort)) on organ function parameters in the serum of hypercholesterolemic and normal rats. Thirty Sprague-Dawley rats were fed high cholesterol diets supplemented with 1.5% PMF(ort) and niacin respectively for 49days. Hypercholesterolemic rats fed PMF(ort) had significant reductions in the activities of aspartate aminotransferase and alkaline phosphatase (69.12±3.34 and 87.22±8.42U/L respectively) compared to the untreated hypercholesterolemic group (118.61±4.85 and 132.62±10.62U/L respectively, p<0.05). Supplementation of the diet with niacin or PMF(ort) resulted in no significant differences in the serum levels of creatinine or urea in any of the groups. Total bilirubin was highest in the untreated hypercholesterolemic group. Supplementation of the diets of hypercholesterolemic rats with PMF(ort) resulted in significant reductions in the activities of serum creatine kinase and lactate dehydrogenase (119.3±25.3; 222.5±50.3U/L, p<0.05) respectively relative to the untreated hypercholesterolemic group (257.2±48.3; 648.8±103U/L, p<0.05). The results would suggest that PMF(ort) modulates hypercholesterolemia-associated organ injury in rats. PMF(ort) could therefore be a suitable candidate for prophylactic and therapeutic treatment of hypercholesterolemia-associated organ injury.

Anti‐nutritional factors, zinc, iron and calcium in some Caribbean tuber crops and the effect of boiling or roasting

Purpose – This study aims to investigate the levels of some anti‐nutritional factors and minerals and the effect of boiling or roasting on selected commonly consumed Caribbean tuber crops.Design/methodology/approach – Three commonly consumed tuber crops in the Caribbean namely: Yellow yam (Dioscorea cayenensis), Cocoyam (Xanthosoma sp.) and Sweet potato (Ipomea batatas) were harvested from farmers’ field in the Parish of Manchester, Jamaica and assessed in their boiled, raw and roasted forms for levels of some anti‐nutritional factors and minerals.Findings – Zinc and iron levels were highest in raw Yellow yam, while the highest levels of calcium were observed in Sweet potato. The phytic acid to zinc molar ratio was higher than 15 in all the tuber crops in their raw and roasted forms. Boiling reduced this ratio to below 15 for Yellow yam and Cocoyam but still remained above 15 for Sweet potato. Cyanoglucoside level was highest in raw Sweet potato followed by Yellow yam and Cocoyam. Boiling or roasting redu...

Carbohydrate digestion and intestinal ATPases in streptozotocin-induced diabetic rats fed extract of yam (Dioscorea cayenensis) or dasheen (Colocasia esculenta)

Abstract Streptozotocin-induced diabetic rats were maintained for four weeks on extracts of yam or dasheen or commercial linamarin. The levels of blood glucose, digestive and membrane-bound enzymes of the intestine were determined. Rats fed commercial linamarin significantly lowered blood glucose level compared to the diabetic rats fed normal diet. Feeding of commercial linamarin to diabetic rats significantly decreased the activity of intestinal amylase compared to normal rats. Dasheen extract or commercial linamarin significantly increased the activities of intestinal disaccharidases compared to the diabetic rats fed normal diet. Na + /K + ATPase activity in the lower segment of the intestine was significantly reduced in diabetic rats compared to normal rats. In the upper segment of the intestine, yam or dasheen extract or commercial linamarin supplementation increased the activity of this enzyme above normal. These observations show that the hypoglycemic property of cyanoglucoside extract from dasheen and to a lesser extent yam, could be due to other chemical constituents of the extract and this needs further investigation.

Alterations in intestinal morphology of streptozotocin-induced diabetic rats fed Jamaican bitter yam (Dioscorea polygonoides) steroidal sapogenin extract

In this study, the effect of yam steroidal sapogenin extract on intestinal morphology in streptozotocin-induced diabetic rats was examined. Diabetic male Wistar rats (n = 32) were fed diets supplemented with 1% bitter yam steroidal sapogenin extract or commercial diosgenin for three weeks. The effect on intestinal morphology was assessed. The induction of diabetes significantly increased villus length and crypt depth compared to the normal group. Supplementation of the diet with sapogenin extract or commercial diosgenin significantly increased villus width compared to the diabetic controls. The dietary supplements also significantly decreased crypt depth towards that of the normal controls. This study shows that the feeding of bitter yam steroidal sapogenin extract to diabetic rats may result in alterations in the intestinal morphology.

The effect of phytic acid on the levels of blood glucose and some enzymes of carbohydrate and lipid metabolism.

In this study, six groups of rats were fed as follows: Groups 1 and 2 were fed formulated diets supplemented with zinc or without zinc respectively. Groups 3 and 4 were fed formulated diets supplemented with zinc plus phytic acid extracted from sweet potato (Ipomea batatas) or commercial phytic acid respectively. Groups 5 and 6 were fed formulated diets supplemented with phytic acid extract from sweet potato or commercial phytic acid respectively. The animals were fed for three weeks and then sacrificed The activities of key enzymes of carbohydrate and lipid metabolism as well as transaminases in the liver were determined. Blood glucose level was also assessed. Phytic acid extract consumption from sweet potato and commercial phytic acid plus zinc supplement lowered blood glucose levels. There was no significant change in the activity of 6-phosphogluconate dehydrogenase among the groups. Similarly, phytic acid supplementation showed no significant decrease in the activity of pyruvate kinase compared to the group fed formulated diets. There was a significant increase in the activity of glucose-6-phosphate dehydrogenase in the groups fed phytic extract from sweet potato compared to the other groups. The activities of malic enzyme and ATP-citrate lyase in this study were not significantly altered among the groups. There is a lowering of blood glucose levels which is desirable for diabetics who consume sweet potato diets. The changes in some of the hepatic metabolic enzymes are geared towards compensating for the decreased glycolytic responses.

DEVELOPMENT OF SALT ADAPTATION IN IN VITRO GREATER YAM (DIOSCOREA ALATA) PLANTLETS

SummaryThe development of plants capable of growing under saline conditions is one approach at utilizing saline soils that are otherwise arable. This study was designed to develop salt-tolerant yam (Dioscorea alata) plantlets, using tissue culture techniques. Salt-tolerant yam (Dioscorea alata cv. Sweet yam) plantlets were produced in vitro through repeated culturing and selection on saline media. Two hundred plantlets were subcultured on normal multiplication media (Murashige and Skoog basal media with 30 gl−1 sucrose and 0.44 μM benzylaminopurine). A further 400 plantlets were equally subcultured on multiplication media supplemented with 100 or 200 mM NaCl. Plantlets that proliferated on medium with 100 mM saline conditions were repeatedly subcultured on saline media. Growth of plantlets and root formation were assessed along with some biochemical parameters such as invertase (EC 3.2.1.26), peroxidase (EC 1.11.1.7), and polyphenol oxidase (EC 1.10.3.1) activities. No growth was observed for plantlets transferred to the highly saline media of 200 mM NaCl and the explants did not survive beyond 6 wk. Control plantlets exhibited 100% rooting within 3 wk compared to 5 wk for plantlets on 100 mM NaCl. Development of new nodes and leaves were observed for plantlets on 100 mM NaCl, although at an initially slower rate than the control plantlets. The enzyme activity profiles obtained for plantlets on 100 mM NaCl reflected the biochemical adjustments of the plantlets to cope with the saline conditions. This was further substantiated by the detection of two reproducible bands of sizes 1 and 0.35 kb from reverse transcription polymerase chain reaction (RT-PCR) studies of salt-tolerant yam plantlets. These results can be translated into efforts aimed at maximizing the use of saline soils.

The interplay between yam (Dioscorea sp.) starch botanical source, micromeritics and functionality in paracetamol granules for reconstitution

A comparative investigation of the interplay between starch botanical source, micromeritics and their functionality in formulated paediatric paracetamol granules for reconstitution was conducted using starches extracted from five local yam (Dioscorea spp.) species. Significant differences were observed in the physicochemical properties of the different starches studied (p<0.05). The observed differences in paracetamol dissolution correlated well with the physicochemical properties of the starches. Granules formulated with Chinese yam and Bitter yam starches showed the fastest rate of paracetamol dissolution with T(80) of 2.2 and 2.6 min, respectively, at 2.5%w/w, and 3.75 and 4.00 min, respectively, at 10% w/w binder concentrations. Those formulated with Round leaf yellow yam starch had the slowest dissolution rate with T(80) of 4.5 and 8.75 min, respectively, at 2.5% and 10% binder concentrations. The results generally indicate a significant dependence of the rate of paracetamol dissolution from granules on starch surface tension, viscosity, swelling power and water binding capacity, particle size distribution, specific surface and porosity. These, in turn, were found to be starch botanic source-dependent suggesting careful consideration of botanic source when substituting one starch product for another in granule formulation.

Effect of yam (Dioscorea cayenensis) and dasheen (Colocassia esculenta) extracts on the kidney of streptozotocin-induced diabetic rats.

Streptozotocin-induced diabetic wistar rats were maintained for 4 weeks on a supplement of extracts of yam (Dioscorea cayenensis) or dasheen (Colocassia esculenta). The activities of malic enzyme, NADP + isocitrate dehydrogenase, Glucose 6-P-dehydrogenase and the transaminases were determined to assess any degree of metabolic alteration caused by diabetic nephropathy. Diabetic rats fed normal diet and those fed yam extract, dasheen extract and commercial linamarin respectively lost weight significantly compared to healthy controls. The diabetic rats fed dasheen extract, maintained near normoglycaemic values compared to diabetic rats on normal diet (P < 0.05). Malic enzyme activity was significantly reduced (P < 0.05) in diabetic rats on the normal diet compared to normal healthy controls. Feeding of yam or dasheen extract raised the activity of this enzyme towards normal. Feeding of dasheen extract or commercial linamarin significantly lowered (P < 0.05) the activity of NADP + isocitrate dehydrogenase below that of healthy controls. Glucose 6-P-dehydrogenase activity was significantly increased (P < 0.05) in diabetic rats compared to healthy controls. Alanine transaminase in the kidney of diabetic rats fed yam extract was significantly higher than healthy controls (P < 0.05). These results demonstrate an overall aggravation of the diabetic nephropathy by yam and dasheen extracts in the diet. In the Caribbean region where these foods are dietary staples, there may be a correlation with the reported high prevalence of diabetes mellitus and the development of renal disease.Streptozotocin-induced diabetic wistar rats were maintained for 4 weeks on a supplement of extracts of yam (Dioscorea cayenensis) or dasheen (Colocassia esculenta). The activities of malic enzyme, NADP+ isocitrate dehydrogenase, Glucose 6-P-dehydrogenase and the transaminases were determined to assess any degree of metabolic alteration caused by diabetic nephropathy. Diabetic rats fed normal diet and those fed yam extract, dasheen extract and commercial linamarin respectively lost weight significantly compared to healthy controls. The diabetic rats fed dasheen extract, maintained near normoglycaemic values compared to diabetic rats on normal diet (P < 0.05). Malic enzyme activity was significantly reduced (P < 0.05) in diabetic rats on the normal diet compared to normal healthy controls. Feeding of yam or dasheen extract raised the activity of this enzyme towards normal. Feeding of dasheen extract or commercial linamarin significantly lowered (P < 0.05) the activity of NADP+ isocitrate dehydrogenase below that of healthy controls. Glucose 6-P-dehydrogenase activity was significantly increased (P < 0.05) in diabetic rats compared to healthy controls. Alanine transaminase in the kidney of diabetic rats fed yam extract was significantly higher than healthy controls (P < 0.05). These results demonstrate an overall aggravation of the diabetic nephropathy by yam and dasheen extracts in the diet. In the Caribbean region where these foods are dietary staples, there may be a correlation with the reported high prevalence of diabetes mellitus and the development of renal disease.