Takanori Kasai

Nutritional evaluation of wild yam (Dioscorea spp.) tubers of Nepal

Abstract Wild yams make a significant contribution to diets of tribal people in Nepal. However, there is insufficient study of their nutritional value. In this paper, four wild yam species: Dioscorea bulbifera, D. versicolor , D. deltoidea and D. triphylla , were studied. The dry matter ranged from 19.8 to 30.5% on a fresh weight basis. The ranges of crude protein, ash, crude fat and crude fibre contents were 1.6–3.1, 0.5–1.2, 0.2–0.3 and 0.6–1.5% of fresh weight, respectively. The ranges of minerals in mg per 100 g fresh weight were K (250–560), Na (4.15–17.8), P (33.1–61.6), Ca (14.3–46.9), Mg (18.3–27.3), Cu (0.10–0.21), Fe (0.39–2.92), Mn (0.14–0.35) and Zn (0.22–0.53). Sulfur-containing amino acids and lysine were the most limiting in all species studied. Nutritional compositions of wild yams were similar to those reported for most cultivated yams in several parts of the world except for the higher value of crude fibre found in our samples.

Increases in calcium absorption with ingestion of soluble dietary fibre, guar-gum hydrolysate, depend on the caecum in partially nephrectomized and normal rats.

Effects of feeding soluble dietary fibre on apparent Ca absorption and the contribution of the caecum to Ca absorption were examined in five-sixths nephrectomized (NPX) and normal rats with or without caecectomy in four experiments. It is known that Ca absorption is lowered by renal failure. In the first experiment the amounts of femur Ca increased linearly with increasing dietary Ca up to 3.0 g Ca/kg diet in intact rats. Partial nephrectomy decreased apparent Ca absorption in rats fed on diets containing 3-0 and 4.5 g Ca/kg diet. In the NPX groups, Ca absorption in rats fed on the diet containing guar-gum hydrolysate (GGH; 50 g/kg diet; 3.0 g Ca/kg diet) was significantly higher than that in rats fed on a fibre-free diet, and the increase in Ca absorption with GGH feeding was completely abolished by caecectomy. Also, ingestion of GGH increased Ca absorption in normal rats, but not in normal, caecectomized rats. Mg absorption was also increased with GGH feeding and was decreased with caecectomy in NPX and normal rats. In experiments which used caecectomized rats, coprophagy was prevented with an anal cup to avoid re-ingestion of faecal Ca. We conclude that ingestion of the soluble dietary fibre, GGH, increased apparent Ca absorption in NPX and non-NPX rats, and the caecum was responsible for these increases in Ca absorption.

Structure-activity Relationships for α-Glucosidase Inhibition of Baicalein, 5,6,7-Trihydroxyflavone: the Effect of A-Ring Substitution

In order to estimate the effects of the A-ring hydroxyl group of baicalein (5,6,7-trihydroxyflavone, 1) on rat intestinal α-glucosidase inhibition, flavone, monohydroxyflavones, dihydroxyflavones, and methylated derivatives of 5,6,7-trihydroxyflavone were used for the structure-activity relationship (SAR) study. The importance of the 6-hydroxyl group of baicalein was validated for an exertion of the activity. And also, the tested flavones which lacked a hydroxyl substituent on any of positions 5, 6, or 7, showed no activity. Hence, the 5,6,7-trihydroxyflavone structure was concluded to be crucial for the potent inhibitory activity. In addition, an introduction of electron-withdrawing or electron-donating groups at position 8 of baicalein led to a dramatic decrease for activity, except for 8-fluoro-5,6,7-trihydroxyflavone, which carried a less bulky substituent on position 8. Hence, this result suggested that a sterically bulky substituent on C-8 of baicalein was detrimental for the activity regardless of its electronic nature. Through examining the inhibitory mechanism of baicalein against rat intestinal α-glucosidase, it was suggested to be a mixed type inhibition.

6-Hydroxyflavonoids as α-Glucosidase Inhibitors from Marjoram (Origanum majorana) Leaves

A methanol extract of marjoram leaves strongly inhibited rat intestinal α-glucosidase. Five 6-hydroxyflavonoids, 6-hydroxyapigenin (scutellarein; IC50 for sucrose hydrolysis by rat intestinal α-glucosidase, 12 μM), 6-hydroxyapigenin-7-O-β-D-glucopyranoside (>500 μM), 6-hydroxyluteolin-7-O-β-D-glucopyranoside (300 μM), 6-hydroxyapigenin-7-O-(6-O-feruloyl)-β-D-glucopyranoside (>500 μM), and 6-hydroxyluteolin-7-O-(6-O-feruloyl)-β-D-glucopyranoside (>500 μM), were isolated as active principles and related compounds. The two feruloylglucosides are novel compounds.

Reduction of allergic airway eosinophilia by dietary raffinose in Brown Norway rats.

Oral administration of raffinose, a naturally occurring indigestible oligosaccharide, has reportedly ameliorated atopic dermatitis in human subjects although the mechanism is unknown. The present study investigated the effect of dietary raffinose on allergen-induced airway eosinophilia in ovalbumin-sensitised Brown Norway rats as an atopic disease model. Brown Norway rats were immunised by subcutaneous injection with ovalbumin on day 0 and fed either a control diet or the diet supplemented with raffinose (50 g/kg diet). The rats were exposed to aerosolised ovalbumin on day 20, and broncho-alveolar lavage fluid was obtained on the next day. The number of eosinophils in the fluid was significantly lower in the rats fed the raffinose diet than in those fed the control diet. Dietary raffinose significantly reduced IL-4 and IL-5 mRNA levels in lung tissue and tended to lower ovalbumin-specific Ig E levels. Suppression of eosinophilia by dietary raffinose was still observed in caecectomised and neomycin-administered rats, suggesting little contribution by the colonic bacteria to the effect of raffinose. Intraperitoneal administration of raffinose also suppressed eosinophilia. Significant concentrations of raffinose were detected in portal venous and abdominal arterial plasma after the intragastric administration of raffinose. Overall, the findings suggest that dietary raffinose ameliorates allergic airway eosinophilia at least partly via post-absorptive mechanisms in Brown Norway rats.

γ-Glutamyl peptides of Vigna radiata seeds

Abstract It has been reported elsewhere that Vigna radiata seeds contain a high concentration of γ-glutamyl- S -methylcysteine and its sulphoxide and that these compounds serve as index compounds for the chemotaxonomy of V. radiata . Beside these two γ-glutamyl peptides, nine other γ-glutamyl derivatives, of which three are new compounds, have been isolated and identified from V. radiata seeds. The structures of the new peptides, γ-glutamyl- S -methylcysteinyl-β-alanine ( S -methylhomoglutathione), γ-glutamyl- N δ -acetylornithine and γ-glutamyl-γ-glutamyl- S -methylcysteine, were confirmed by direct comparison with synthetic specimens. The other six γ-glutamyl derivatives were homoglutathione, γ-glutamyl glutamic acid, -aspartic acid, -phenylalanine, -leucine and -isoleucine.

γ-Glutamyltranspeptidases in the metabolism of γ-glutamyl peptides in plants

Abstract The activity and specificity of γ-glutamyltranspeptidase in immature seeds of some leguminous plants did not reflect the γ-glutamyl peptide pattern

Fermentable property of dietary fiber may not determine cecal and colonic mucosal growth in fiber-fed rats

Abstract Differences in cecal and colonic mucosal weight, DNA, RNA, and protein content were observed after feeding fiber-free or cellulose, sugar-beet fiber (SBF), psyllium- and guar gum-containing diets in Sprague-Dawley male rats in regard to fermentable and physical properties of the dietary fiber. In rats fed a low fermentable viscous fiber, psyllium, protein, RNA, and DNA contents in the cecal mucosa were greater than those in the fiber-free and two insoluble fiber groups. The effects of psyllium feeding on the colonic mucosa were much greater than those of the other groups, except RNA and DNA content in the SBF group. In rats fed a highly fermentable viscous polysaccharide, guar gum, changes in the cecal protein, RNA and DNA content were very similar to those in the psyllium group. In contrast, guar gum feeding did not influence any indications of the colonic mucosa. The ingestion of cellulose did not affect the cecal and colonic mucosa. Effects of a highly fermentable insoluble fiber, SBF, on the cecal mucosa were intermediate between cellulose and soluble fiber groups. Colonic DNA pool in the SBF group was high and comparable to that in the psyllium group. The present study shows that fermentable property is not sole determinant of the mucosal growth of the large intestine by dietary fiber, and the effects of physical stress by dietary fiber on the cecal and colonic mucosa may be greater than stimulation of fermented products.

Quinone Hemiacetal Formation from Protocatechuic Acid during the DPPH Radical Scavenging Reaction

Protocatechuic acid was rapidly converted to protocatechuquinone 3-methyl hemiacetal and protocatechuquinone during the reaction with DPPH radical in methanol. The structure of the acetal was determined by comparing the NMR data with those of an authentic compound prepared by (diacetoxy)iodobenzene oxidation of protocatechuic acid.

A Protein Less Sensitive to Trypsin, Guanidinated Casein, Is a Potent Stimulator of Exocrine Pancreas in Rats

Abstract Previously, we have shown that, in rats that have had bile-pancreatic juice (BPJ) diverted from the proximal small intestine for 7 days, the exocrine pancreatic secretion was enhanced after they were fed a casein, fat-free diet. This demonstrates that the pancreatic secretion is stimulated by dietary protein with a pancreatic protease-independent pathway. To examine the chemical structure of casein responsible for the enhancement of pancreatic secretion, we prepared chemically modified casein in which lysine residues were guanidinated. Secretion of protein, amylase, and chy-motrypsin in the chronic BPJ-diverted rat was increased much more after the rats were fed a diet containing guanidinated casein (250 g/kg diet) than after they were fed a diet containing intact casein (250 g/kg diet). In normal rats whose diverted BPJ was returned to the duodenum, the increases in the pancreatic secretion after consuming the guanidinated casein diet were comparable to those after consuming the intact casein diet. In vitro digestibility of guanidinated casein by trypsin and chymo-trypsin was much lower than that of intact casein. Also, guanidinated casein inhibited tryptic hydrolysis of benzoyl-l-arginine p-nitroanilide to a lesser extent than did intact casein as determined by an in vitro assay. These results demonstrate that guanidinated casein is less sensitive to trypsin than is intact casein and that the structure that is sensitive to trypsin is not involved in the stimulation of pancreatic secretion in diverted rats. The results evidence that masking luminal trypsin activity does not predominantly contribute to the enhancement of pancreatic secretion in 7-day BPJ-diverted rats. Also, in normal rats, the luminal protease-independent mechanism may play a role partly in increasing the pancreatic secretion by dietary protein. [P.S.E.B.M. 1995, Vol 210]