Jun Kawabata

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.

Inhibitory effect on α-glucosidase by Adhatoda vasica Nees

Methanolic extracts from the medicinal parts of 40 traditional Chinese herbs were tested in screening experiments for rat intestinal α-glucosidase. The methanolic extract from the leaves of Adhatoda vasica Nees (Acanthaceae) showed the highest sucrase inhibitory activity with sucrose as a substrate. Enzyme assay-guided fractionation of this extract afforded vasicine (1) and vasicinol (2), and the structures of these compounds were elucidated on the basis of MS and NMR analysis. Compounds 1 and 2 showed a high sucrase inhibitory activity, and the IC50 values were 125μM and 250μM, respectively. Both 1 and 2 were shown to be reversible inhibitors of sucrase. Kinetic data revealed that compounds 1 and 2 inhibited sucrose-hydrolysing activity of rat intestinal α-glucosidase competitively with Ki values of 82μM and 183μM, respectively. This is the first report on the mammalian α-glucosidase inhibition of A. vasica and the inhibitory effect on sucrase by 1 and 2 from this herb species. These results suggest a use of the extract of A. vasica as an antidiabetic agent and show a possibility that compounds 1 and 2 could be an useful treatment for metabolic disorders.

Dimeric sesquiterpenoid esters from Chloranthus serratus

Abstract Three novel dimeric sesquiterpenes, shizukaols, B, C and D, which consist of two lindenane (modified eudesmane) units were isolated from the roots of Chloranthus serratus. Their structures were elucidated by 1D- and 2D-NMR analyses and by chemical methods. Among them, shizukaol B has a unique pendent macrocyclic lactone ring. The biogenetic relationship of the lindenane dimers is briefly discussed.

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.

OLIGOSTILBENES FROM CAREX KOBOMUGI

Abstract A novel tetrastilbene, kobophenol A was isolated from subterranean parts of Carex kobomugi together with the previously known miyabenol C and (−)-e-viniferin. The stereochemistry of kobophenol A and miyabenol C was elucidated as (7a R ,8a R ,7b S ,8b S ,7c S ,8c S ,7d S ,8d R ) and (7a R ,8a R ,7b S ,8b S ), respectively. The biogenetic relationship of all the above compounds is briefly discussed.

Sesquiterpene dimers from Chloranthus japonicus

Five novel dimeric sesquiterpenes, shizukaols E-I, consisting of two lindenane units were isolated from the roots of Chloranthus japonicus. Their structures were elucidated principally by 1D- and 2D-NMR methods. Three of them have a unique pendent macrocyclic ester ring found previously in shizukaol B.

Shizukaol A, A sesquiterpene dimer from Chloranthus japonicus

Abstract A novel dimeric sesquiterpene consisted of two lindenane (modified eudesmane) units was isolated from roots of Chloranthus japonicus . The structure was elucidated by 1D and 2D NMR analyses and by chemical methods.

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.

Importance of the B Ring and Its Substitution on the α-Glucosidase Inhibitory Activity of Baicalein, 5,6,7-Trihydroxyflavone

Hydroxychromones and B-ring-substituted 5,6,7-trihydroxyflavones were prepared to evaluate the contribution of the B ring of baicalein (5,6,7-trihydroxyflavone, 1) to its potent α-glucosidase inhibitory activity. Hydroxychromones, which lack 6-hydroxyl substitution, did not show any inhibitory activity, while 5,6,7-trihydroxy-2-methylchromone (5) showed high activity. Among the tested B-ring-substituted 5,6,7-trihydroxyflavones, the 4′-hydroxy-, 3′,4′-dihydroxy-, and 3′,4′,5′-trihydroxy-substituted derivatives were found to give more activity than that of 1. The methoxy-substituted derivatives, however, showed less activity than 1. The results suggest that the B ring of 1 was not essential, although advantageous to the activity; hydroxyl substitution on the B ring of 5,6,7-trihydroxyflavones was favorable to the activity, whereas methoxyl substitution was unfavorable; at least 4′-hydroxyl substitution of 5,6,7-trihydroxyflavones was required for enhanced activity, in which the number of hydroxyl groups did not take part.

A Phenolic amide from roots of Chenopodium album

Abstract A new phenolic amide has been isolated from the roots of Chenopodium album . Its structure was determined as N-trans -feruloyl-4- O -methyldopamine by spectroscopic evidence and chemical synthesis. It showed attracting activity toward the zoospores of Aphanomyces cochlioides , a pathogenic fungus against some plants of Chenopodiaceae.