Buncha Ooraikul

Dietary rhubarb ( Rheum rhaponticum ) stalk fibre stimulates cholesterol 7α-hydroxylase gene expression and bile acid excretion in cholesterol-fed C57BL/6J mice

Both experimental and clinical studies have indicated that a novel source of dietary fibre, produced from rhubarb (Rheum rhaponticum) stalks, is potentially hypolipidaemic. The present study, using C57BL/6J mice, was undertaken to examine if this fibre source affects cholesterol degradation. Mice were maintained on semi-purified diets containing 50 g rhubarb fibre or cellulose/kg with or without 5 g cholesterol/kg for 4 weeks. In cholesterol-supplemented mice, rhubarb fibre caused significant lowering of plasma cholesterol (-13%) and the hepatic concentrations of total cholesterol (-34%) and cholesteryl esters (-34%). In parallel to the reduction of hepatic cholesteryl ester content, animals fed on rhubarb fibre had significantly lower activity of acyl CoA: cholesterol acyltransferase (EC 2.3.1.26) than the mice maintained on a diet containing cellulose and cholesterol. Rhubarb-fibre feeding accelerated the faecal bile-acid loss and diminished the gall-bladder bile-acid pool in both the normal and the cholesterol-fed mice. The increase in the bile-acid excretion was positively correlated with an increased activity as well as mRNA abundance of cholesterol 7 alpha-hydroxylase (EC 1.14.13.17). The increased excretion of bile acids and induction of cholesterol 7 alpha-hydroxylase activity may account for the hypocholesterolaemic effect of rhubarb fibre.

Cholesterol lowering effects of rhubarb stalk fiber in hypercholesterolemic men

OBJECTIVE The present study was undertaken to examine the lipid lowering effects of rhubarb fiber prepared by blanching and drying fresh rhubarb stalks. The new fiber source contained 74% dietary fiber, on dry weight basis, with 66% insoluble and 8% soluble fiber. DESIGN Ten hypercholesterolemic men were assigned to consume 27 g of ground rhubarb stalk fiber per day for 4 weeks. The dietary intake in terms of total energy, lipid and cholesterol was kept unaltered during the study period. Changes in serum lipid profile were monitored by obtaining blood samples before and after the fiber intervention. RESULTS Rhubarb fiber supplementation resulted in significant lowering of serum total cholesterol (8%) and low-density lipoprotein (LDL) cholesterol (9%), while high-density lipoprotein cholesterol (HDL) concentrations remained unchanged. The depressed total and LDL cholesterol levels returned to baseline after the fiber supplementation was withdrawn for 1 month. CONCLUSION The rhubarb stalk fiber is effective in lowering serum cholesterol concentrations, especially LDL cholesterol, in hypercholesterolemic men. These results signify the potential use of underutilized rhubarb crop.

In vitro binding of bile salt to rhubarb stalk powder

Abstract A new fiber source was developed by blanching, drying and grinding the fresh stalks of rhubarb, an underutilized and universal crop. The product was found to contain 74% total dietary fiber (66% insoluble and 8% soluble dietary fiber), on dry weight basis. Preliminary studies involving experimental animals and hypercholesterolemic subjects revealed that this fiber source is potentially hypolipidemic, though the underlying mechanism still remains unknown. To investigate its mechanism of action, this study was undertaken to determine its potential to complex with bile salts in vitro . Comparison of various fiber sources showed that the rhubarb fiber had the maximum ability to bind taurocholate, and bound 11 and 2.5 fold more bile salt than cellulose and wheat bran respectively. The binding increased linearly with increasing rhubarb fiber concentration. Increasing the bile salt concentration also increased the binding in a dose dependent manner and showed a saturation at a concentration greater than 10mM. The rhubarb fiber had a binding capacity of 40 μmol of taurocholate per gram. Cholate competed taurocholate for binding indicating that conjugation of bile salt was not a mandatory requirement for the binding Based on the chemical composition of rhubarb stalk powder, the bile salt binding property appears to be due to a combination of factors present in this product such as its high fiber content (insoluble with pectin), hydrophilic nature and high ash content. The ability to bind bile salts might be responsible for its hypocholesterolemic action observed in experimental animals and humans.

Effect of pre-cooking in potato granule production by a freeze-thaw process

SummarySteam-cooked potatoes pre-cooked for 20 min at 70 C were firmer than those cooked without pre-treatment. The product remained intact and required a greater force for subdivision into smaller aggregates. Excessive cell damage was sustained during the mashing step of the freeze-thaw (F-T) process, resulting in a gluey mash which could not be easily processed into granules. The pectic substances of the potatoes with pre-treatment were less solubilized than those cooked without. This suggested that they were made more resistant to thermal degradation by pre-cooking, resulting in greater intercellular cohesion and less rarefaction of the cell wall during subsequent cooking. Cell separation was poor in the following F-T process. Electron photomicrographs showed that precooking gelatinized the starch and that the cell wall remained unseparated.ZusammenfassungGedämpfte Kartoffeln, 20 Minuten bei 70±1 C vorbehandelt, wiesen eine festere Konsistenz auf als solche ohne Vorbehandlung (Tab. 2). Dieses Produkt blieb eher intakt und es erforderte mehr mechanische Arbeit, um es in kleinere Bruchstücke zu zerteilen, die eine Vorbedingung des Gefrier-Tau-Verfahrens (G-T-Verfahren) sind. Dies verursachte grössere Schäden, die zur Bildung eines klebrigen Breis führten (Tab. 3), der mit dem G-T-Verfahren nicht zu Granulat verarbeitet werden konnte. Trotz einiger Änderungen des Verfahrens, z.B. längeres Pürieren und tiefere Trocknungstemperatur, war die Ausbeute an Granulat gering und die Anzahl der verletzten Zellen hoch (Tab. 1).So behandelte Kartoffeln zeigten eine geringere Löslichkeit pektinartiger Verbindungen (672.2 mg Galakturonide pro 100 g Trockenmasse) als gedämpfte Kartoffeln ohne Vorbehandlung (1106 mg/100 g Trockenmasse). Das Dämpfen allein schien alle pektinartigen Substanzen in Lösung zu bringen, während ein Drittel des Pektins ungelöst blieb, wenn die Kartoffeln vorbehandelt wurden (Tab. 4). Dies lässt vermuten, dass durch die Vorbehandlung die pektinartigen Substanzen gegen weitere Hitzeeinflüsse resistent werden, was zu einer Verminderung des Verlustes des interzellulären Zusammenhaltes sowie einem verminderten dünner werden beim darauffolgenden Dämpfen führt. Deshalb war das Kartoffelgewebe fester als dasjenige, welches nicht vorbehandelt wurde.Elektronenmikroskopische Untersuchungen zeigten, dass das Vorkochen die Stärke gelatinisierte und die Zelle lose füllte, während die meisten Zellwände aneinander haften blieben (Abb. 2 und 3). Da die Bindungskräfte zwischen den Zellen sogar nach dem Dämpfen gut erhalten blieben, war die Zellabspaltung im darauffolgenden G-T-Verfahren gering (Abb. 8–11).RésuméLes pommes de terre cuites à la vapeur après avoir subit une précuisson pendant 20 min à 70±I C sont plus fermes que celles obtenues sans précuisson (tableau 2). Un tel produit a tendance a rester intact et demande une plus grande action mécanique pour être reduit en particules plus petites lors de la mise en purée par la méthode requise lors du procédé ‘freezethaw’ (F-T). Ceci entraine des domages importants des cellules, rendant la purée collante et impropre à la granulation lors du procédé F.T. (tableau 3). Même par le biais de quelques modifications du procédé, e.g. un malaxage plus long de la purée et une température de séchage inférieure, le rendement en granules reste faible et le nombre de cellules broyées trés élevé (tableau 1).Les pommes de terre subissant ce traitement présentent une faible solubilisation des substances pectiques (673.2 mg d’uronide par 100 g de matière sèche) comparé aux pommes de terre cuites sans précuisson (1106 mg/100 g de matière sèche). La cuisson à la vapeur semble solubiliser à elle seule toutes les substances pectiques utilisables alors qu’un tiers de la pectine reste insolubilisée lorsque le produit a subit une précuisson (tableau 4). Ceci suggère que la précuisson rend les substances pectiques plus resistantes à toute dégradation thermique successive, diminuant la perte de liaisons entre les cellules et raréfiant la séparation des parois cellulaires lors de la cuisson. Donc, les tissus obtenus sont plus fermes que ceux qui n’ont pas reçu de prétraitement.Des photos au microscope électronique montrent que la précuisson gélatinise l’amidon qui remplit alors tout le volume cellulaire tandis que la plupart des parois cellulaires restent liées les unes aux autres (figures 2 et 3). Les forces de liaison entre cellules restant donc importantes même après cuisson à la vapeur, la séparation des cellules est mauvaise lors des étapes suivantes du procédé F-T (figures 8 à 11).

The lipid-lowering effects of rhubarb stalk fiber: A new source of dietary fiber

Abstract Dried and ground rhubarb stalk fiber containing, on a dry weight basis, 74% total dietary fiber (66% insoluble and 8% soluble) was prepared from rhubarb plants grown in the province of Alberta, Canada. Effect of this fiber source on the plasma and liver concentrations of cholesterol and triglycerides as well as the hepatic microsomal activities of β-hydroxy β-methyl coenzyme A reductase (HMGR) and acyl CoA: cholesterol acyl transferase (ACAT) were examined in mice receiving ad libitum a semi-synthetic diet containing 0.5% cholesterol. Feeding the cholesterol-enriched diet for 4 weeks in the presence of 5% rhubarb stalk fiber resulted in significantly lower plasma concentrations of cholesterol and triglycerides as well as hepatic concentrations of total cholesterol than those of animals receiving the diet where rhubarb fiber was substituted by 5% cellulose fiber. Dietary cholesterol supplementation accelerated ACAT activity. In the presence of 5% rhubarb fiber in the diet, this activity was restored to the level found in animals fed a cholesterol-free diet. On the other hand HMGR activity was inhibited by cholesterol supplementation and remained unaffected by addition of rhubarb fiber. These results indicate that rhubarb stalk fiber has a lipid-lowering effect which may not be mediated via alterations in the synthesis and metabolism of cholesterol.

Effect of dietary rhubarb stalk fiber on the bioavailability of calcium in rats

Ground rhubarb stalk fiber containing, on a dry weight basis, 74% total dietary fiber (66% insoluble and 8% soluble) was prepared from rhubarb plants. This fiber source has been shown to have a pronounced lipid lowering effect in mice. Its high oxalic acid content may, however, be a limiting factor for its use. The present study was undertaken to determine the safe dose level of the fiber in terms of its effect on calcium bioavailability. Male weanling Sprague-Dawley rats were fed a semi-purified diet (AIN 76) for 4 weeks containing 0, 1, 3, or 5% rhubarb fiber, or pure oxalic acid equivalent to 5% rhubarb fiber. The fiber content of each diet was brought to 5% by adding cellulose, and the calcium level of all diets was the same. As the rhubarb stalk fiber content of the diet increased, a consistent trend of increasing total retention and apparent absorption of calcium was manifested. In contrast, however, cellulose, due to its increased effect on intestinal motility resulted in a decreased calcium bioavailability. Overall results suggest that an addition of rhubarb stalk powder up to the level of 5% in a diet does not have detrimental effect on calcium bioavailability.

Effects of dietary pectin on the hepatic activities of hydroxymethyl glutaryl CoA reductase and acyl CoA cholesterol acyltransferase in cholesterol supplemented mice

Abstract Plasma lipoprotein cholesterol and hepatic activities of hydroxymethyl glutaryl CoA reductase (HMGR) and acyl CoA cholesterol acyltransferase (ACAT) in mice fed a semi-synthetic diet supplemented with 5% low methoxyl pectin with or without addition of 0.5% cholesterol for 4 weeks were examined. While plasma concentrations of total cholesterol and triglycerides were significantly reduced, the hepatic levels of total and esterified cholesterol were markedly increased, and triglyceride levels remained unaffected when cellulose in the diet was substituted for by pectin in the cholesterol-enriched diet. The administration of 0.5% cholesterol to control animals resulted in a 50% reduction in the hepatic HMGR activity. This activity was restored to its control level when cellulose was substituted by pectin in the diet. The hepatic ACAT activity, on the other hand, was significantly increased when fed a diet containing 0.5% cholesterol. This effect remained unchanged when pectin was administered. The hypolipidemic action of pectin does not appear to be mediated through inhibition of cholesterol synthesis. It is possible that the decreased plasma level of cholesterol is the reflection of its accumulation in the liver.