A roselle (Hibiscus sabdariffa Linn.) tea extract was found to have high inhibitory activity against porcine pancreatic alpha-amylase. Hibiscus acid and its 6-methyl ester were respectively isolated as active principles from the 50% methanol and acetone extracts of roselle tea. The activity of each isolate was compared to that of structurally related citric acid, a previously known inhibitor of fungal alpha-amylase.
Germinated grains have been known as sources of Gamma-aminobutyric acid (GABA) that provide beneficial effects for human health. This study was aimed to investigate GABA production, dietary fiber, antioxidant activity, and the effect of cooking on GABA loss in germinated legumes and sesame. The highest GABA content was found in germinated mung bean, (0.8068 g kg-1 , 24 h incubation) followed by germinated soybean, germinated black bean and soaked sesame. Beside GABA, dietary fiber content also increased in all grains during germination where the insoluble dietary fiber fractions were always found in higher proportions to soluble dietary fiber fractions. Dur results also confirmed that germinated mung bean is a rich source of GABA and dietary fibers. Microwave cooking resulted in the smallest loss of GABA in mung bean and sesame, while steaming led to the least GABA content loss in soybean and black bean. Therefore microwave cooking and steaming are the most recommended cooking processes to preserve GABA in germinated legumes and sesame.
The aim of this research was to investigate the extraction yield and physicochemical properties of sago starch extracted after enzymatic pretreatment. Sago pith was enzymatic-pretreated by varying enzyme (cellulase enzyme complex) concentration, pretreatment time, and sago pith slurry concentration. The extracted sago starch was analyzed for its properties, e.g., extraction yield, pasting and thermal properties, and in vitro starch digestibility. Sago pith contained 82% (db) starch. The extraction yield and reducing sugar released increased with enzyme concentration and pretreatment time. The optimum enzymatic pretreatment conditions were 10% (w/w) sago pith slurry, enzyme concentration of 0.25 mL (618 carboxymethylcellulose unit and 139 p-nitrophenyl-b-D-glucopyranoside unit)/g substrate, and 24 h pretreatment time, providing the highest extraction yield of 71.36% (w/w sago pith, db), while control method, without enzymatic pretreatment, provided 61.01% extraction yield. Results from pasting and thermal properties confirmed that the granular stability, resistance to shear, and crystalline perfection of sago starch were improved due to hydrothermal effect of annealing during enzymatic pretreatment. The enzymatic-pretreated sago starch also had lower retrogradation but higher starch digestibility than the control sago starch. The enzymatic pretreatment enhanced the extraction yield of sago starch and also improved its quality by the effect of annealing.
Hibiscus acid, an alpha-amylase inhibitor isolated from roselle tea, and its derivatives were compared in an inhibition test for starch digestion. An alpha-amylase-added Caco-2 system was established as a useful model to evaluate the effects of alpha-glucosidase inhibitors on starch digestion. Hibiscus acid showed weak inhibition in this model system, and the methyl ester derivatives showed even weaker or no acitivity.
Sago starch extracted from the pith of sago palm using a traditional method has a low extraction yield. In this study, an effective extraction method for sago starch production with high extraction yield and acceptable starch quality was investigated using various pretreatment techniques, that is, ultrasonic, microwave, and enzymatic pretreatments, as well as combined pretreatment methods. The sago pith slurry was pretreated before subjecting to the normal process of sago starch extraction. The extracted sago starch was analyzed for extraction yield and physicochemical properties. Sago pith had high starch content of 82.0% (db). The highest extraction yields obtained using ultrasonic, microwave, enzymatic, and combined ultrasonic–enzymatic pretreatment methods were 71.5, 63.7, 71.4, and 72.5%, respectively, while the control method (without pretreatment) provided 61.0% extraction yield. The peak viscosity and color L* value of all extracted sago starches met the requirements of edible sago starch. Concerning the effective pretreatment method in terms of reduced time and energy consumption, while providing high extraction yield and acceptable starch quality, the ultrasonic pretreatment was recommended. The highest yielding ultrasonic pretreatment conditions were found to be 10% w/w sago pith slurry, 160 W power input, and 7 min pretreatment time.
In addition to their use as food, mushrooms have been gaining importance in medicinal practices. Beta glucan, known as a modulator of the immune system, is one of the bioactive compounds of interest. This study explores the relationship between environmental variables and spatial distribution of mushroom communities containing betaglucan using Canonical Correspondence Analysis. Mushroom samples were collected for study from 125 sampling points within three sites in seven subtypes of subtropical dry forest along elevational gradients with a variety of ecosystems and climates from Thung Salaeng Luang National Park in the lower North of Thailand. Most mushrooms in the family Russulaceae, growing in deciduous dipterocarp forests and mixed deciduous forests with bamboo in the northern and the central-western parts of the park, and Polyporaceae, found in dry evergreen forests, were found to have relatively high beta glucan content. Mushroom communities could be categorized into five groups by cluster analysis using the Sorensen (BrayCurtis) distance technique with remaining information of 75%; the groups were named according to altitude and forest type. It was found that the high beta glucan content mushroom community consisting of Pycnoporus cinnabarinus, P. coccineus, and P. sanguineus mostly occurred in the highland dry evergreen forest habitat. It is also shown that the occurrence of high beta glucan content mushroom communities is correlated with the specific habitat characteristics of high altitude, high crown cover percentage and high rainfall.
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