Galacturonic Acid Content Research Articles

Optimisation of acid extraction of pectin from sweet potato residues by response surface methodology and its antiproliferation effect on cancer cells

SummaryThe response surface methodology was employed to study the acid extraction of pectin from sweet potato residues. The effects of extraction temperature, extraction time, solution pH and liquid/solid ratio on yield and galacturonic acid content of pectin were investigated. Experimental data were fitted to quadratic polynomial models and analysed using appropriate statistical methods. The determined optimum conditions were extraction temperature 93 °C, extraction time 2.2 h, solution pH 1.7 and liquid/solid ratio (v/w) 30:1. Under these conditions, the experimental extraction yield and galacturonic acid content of pectin were 5.09% and 70.03% (w/w), which were in good agreement with predicted values, 5.08% and 69.40%, respectively. In addition, sweet potato pectin exhibited remarkable antiproliferation effects on human colon cancer cells HT‐29 and human breast cancer cells Bcap‐37 by 46.64% and 42.64% at 1.00 mg mL−1 separately, indicating that it could potentially be used as a natural supplement in functional foods.

Protective effects of galacturonic acid-rich vinegar brewed from Japanese pear in a dextran sodium sulfate-induced acute colitis model

The effects of pear vinegar (PV), which was specially brewed for enhanced galacturonic acid content, on the DSS-induced ulcerative colitis (UC) mouse model were evaluated. PV improved clinical symptoms, colon inflammation, and histological tissue injury in the DSS-induced acute UC mouse model. Moreover, PV suppressed inflammation due to acute UC by suppressing the myeloperoxidase (MPO)-mediated activation of inflammatory cells such as leukocytes and decreasing the serum concentration of IL-6. Our results demonstrated the protective action of PV in the DSS-induced acute UC mouse model. On the other hand, commercial apple vinegar did not show a protective effect in the DSS-induced acute UC mouse model. Our findings indicate that PV may act as a new functional food for inflammatory bowel disease patients.

Preparation, preliminary characterization and immunostimulatory activity of polysaccharide fractions from the peduncles of Hovenia dulcis

The peduncles of Hovenia dulcis, containing abundant nutrients and having a taste like a combination of raisin, clove, cinnamon and sugar, have been consumed as fruits and used as traditional herbal medicine for a long time in China. Up to date, little information is available about the polysaccharides from peduncles of H. dulcis (HDPS) and their potential bioactivity. In this study, three purified fractions were prepared by sequential purification of crude HDPS through ion-exchange chromatography and gel-filtration chromatography. The three fractions of HDPS-1, HDPS-2 and HDPS-3 were found to be homogeneous heteropolysaccharides mainly composed of rhamnose, arabinose, galactose and galacturonic acid with an average molecular weight of 235, 70 and 53kDa, respectively. HDPS-3 was quite different from HDPS-1 and HDPS-2, as it contained much higher content of galacturonic acid (40.5%). In vitro immunostimulatory activity evaluation revealed that all the three fractions could significantly stimulate the proliferation of splenocytes and enhance phagocytosis, nitric oxide production and acid phosphatase activity of peritoneal macrophages, which suggested that HDPS had a potent immunostimulatory activity and could be explored as a potential natural immunomodulatory agent.

Structural Characteristics of Pumpkin Pectin Extracted by Microwave Heating

To improve extraction yield of pumpkin pectin, microwave heating was adopted in this study. Using hot acid extraction, pumpkin pectin yield decreased from 5.7% to 1.0% as pH increased from pH 1.0 to 2.0. At pH 2.5, no pectin was recovered from pumpkin flesh powder. After a pretreatment at pH 1.0 and 25 °C for 1 h, pumpkin powder was microwave-extracted at 120 °C for 3 min resulting in 10.5% of pectin yield. However, premicrowave treatment at 60 °C for 20 min did not improve extraction yield. When microwave heating at 80 °C for 10 min was applied after premicrowave treatment, final pectin yield increased to 11.3%. When pH was adjusted to 2.0, the yield dropped to 7.7% under the same extraction conditions. Molecular shape and properties as well as chemical composition of pumpkin pectin were significantly affected depending on extraction methods. Galacturonic acid content (51% to 58%) of pumpkin pectin was lower than that detected in commercial acid-extracted citrus pectin, while higher content of neutral sugars and acetyl esters existed in pumpkin pectin structure. Molecular weight (M(w) ) and intrinsic viscosity (η(w) ) determined for microwave-extracted pumpkin pectins were substantially lower than acid-extracted pectin, whereas polydispersity was greater. However, microwave-extracted pectin at pH 2.0 had more than 5 times greater M(w) than did the pectin extracted at pH 1.0. The η(w) of microwave-extracted pectin produced at pH 2.0 was almost twice that of other microwave-extracted pectins, which were comparable to that of acid-extracted pectin. These results indicate that extraction yield of pumpkin pectin would be improved by microwave extraction and different pectin structure and properties can be obtained compared to acid extraction. Pumpkin is a promising alternative source for pectin material. Pumpkin pectin has a unique chemical structure and physical properties, presumably providing different functional properties compared to conventional commercial pectin sources. Depending on the conditions to produce pumpkin pectin, diverse molecular structures can be obtained and utilized in various food applications.

Stabilization of emulsions by gum tragacanth (Astragalus spp.) correlates to the galacturonic acid content and methoxylation degree of the gum

Gum tragacanth samples from six species of Iranian Astragalus bush plants (“goat's-horn”) were evaluated for their emulsion stabilizing effects and their detailed chemical composition in order to examine any possible correlation between the make-up and the emulsion stabilizing properties of gum tragacanth. The six gum tragacanth samples were exudates from the species Astragalus parrowianus, Astragalus fluccosus, Astragalus rahensis, Astragalus gossypinus, Astragalus microcephalus, and Astragalus compactus. The six gum samples varied with respect to their levels and ratios of water-soluble (tragacanthin) and water-swellable (bassorin) fractions, their monosaccharide composition, methoxylation, and acetylation degrees. The gums from A. parrowianus and A. fluccosus had relatively high tragacanthin:bassorin ratios of ∼66:34 and ∼75:25, respectively, whereas in the other gums this ratio approached 50:50 (A. rahensis, A. microcephalus, A. compactus) or tipped toward higher bassorin than tragacanthin (A. gossypinus). The monosaccharide make-up of the six gums also varied, but all the gums contained relatively high levels of galacturonic acid (∼100–330 mg/g), arabinose (50–360 mg/g), xylose (∼150–270 mg/g), and galactose (∼40–140 mg/g), and also contained fucose, rhamnose, and glucose. The ability of the gums to act as stabilizers in whey protein isolate based emulsions varied. The best emulsion stabilization effect, measured as lowest creaming index ratio after 20 days, was obtained with the A. fluccosus gum. The emulsion stabilization effect correlated linearly and positively to the methoxylation degree, and galacturonic acid content of the gums, but not to acetyl or fucose content. A particularly high correlation was found between methoxyl level in the soluble gum part and emulsion stabilization. The work provides some important clues to the emulsion stabilization mechanisms in relation to the monosaccharide composition of tragacanth gums.

Characterization of sugar beet pectic-derived oligosaccharides obtained by enzymatic hydrolysis

Three pectic oligosaccharides (POS) obtained by enzymatic hydrolysis of sugar beet pectin by combining endopolygalacturonase and pectinmethylesterase, were characterized using high performance liquid chromatography, thermogravimetric analysis, Fourier transform infrared spectroscopy, differential scanning calorimetry and X-ray diffraction. According to chromatographic analyses, POS are composed of mixture of polymers with different molecular weights and different galacturonic acid contents. The thermal analysis showed no major variation in thermal behavior regarding POS composition but showed that POS were more sensitive to thermal degradation than the parent pectin as well as the deesterified pectin. No change in composition of the gaseous products was obtained through TGA-FTIR analysis. The X-ray pattern of POS clearly indicated a considerable decrease in crystallinity when compared to the native pectin. Thus, thermal characterization of POS may have practical repercussions if the formulation in which POS is incorporated is submitted to a high temperature treatment.

Sustainable production of pectin from lime peel by high hydrostatic pressure treatment

The application of high hydrostatic pressure technology for enzymatic extraction of pectin was evaluated. Cellulase and xylanase under five different combinations (cellulase/xylanase: 50/0, 50/25, 50/50, 25/50, and 0/50U/g lime peel) at ambient pressure, 100 and 200MPa were used to extract pectin from dried lime peel. Extraction yield, galacturonic acid (GalA) content, average molecular weight (Mw,ave), intrinsic viscosity [η]w, and degree of esterification (DE) were compared to those parameters obtained for pectins extracted using acid and aqueous processes. Pressure level, type and concentration of enzyme significantly (p<0.05) influenced yield and DE of pectin. Enzyme and high pressure extraction resulted in yields which were significantly (p<0.05) higher than those using acid and aqueous extraction. Although pressure-induced enzymatic treatment improves pectin yield, it does not have any significant effect on Mw,ave and [η]w of pectin extracts indicating the potential of high pressure treatment for enzymatic pectin production as a novel and sustainable process.

Preparation of Pectin from Fruit Peel of Citrus maxima

The extraction of high-methoxyl pectin from the fruit peel of Citrus maxima was studied. The suitablecondition was the extraction at 80 °C without pH adjustment (pH was about 4.5) in 20 times by volume ofwater. For up-scale procedure, the peel was pre-soaked in water for overnight to wash out small molecularwater-soluble substances. Amberlite XAD-16 polystyrene was used to remove phenolic compounds beforeconcentration and precipitation of pectin. This suggested method was simple and inexpensive. The yieldof the obtained pectin was 7.23±0.19%. Its galacturonic acid content and degree of esterification were74.12±2.07% and 76.30 ±3.38%, respectively. Key Words: Citrus maxima; Galacturonic acid; High-methoxyl pectin; Pomelo; Up-scale production

A Study of the Extraction of Pectin from Dried Lemon Peels

Pectin was extracted from dried lemon peels using acid hydrolysis. Five process variables/factors were chosen for investigation; the extraction temperature, extraction time, pH, size of the peels and the peel to water mass ratio. Three response variables were monitored; the Yield (% Yield), Degree of Esterification (% DE) and Galacturonic Acid content (% GA). A duplicated 25 factorial design was conducted on dried peels. The extraction temperature, time, pH and size of the peel were found to be the most significant variables affecting the pectin yield. The most significant variable affecting the % GA was found to be the extraction time and the % DE was most significantly affected by the pH as well as the extraction temperature. A duplicated 24 design (peel size excluded as a process variable) on fresh wet peels was conducted in order to compare the results attained to those of dried peel extraction. Drying the peel therefore increased the greatest pectin yield attained, it had no drastic effect on the % GA, but it reduced the % DE of the pectin extract. A 24 design was also performed on wet peels that had been stored at atmospheric conditions for two days. The results were compared to those found from fresh wet peel extraction, in order to depict the need for drying the peel.

A copolymer analysis approach to estimate the neutral sugar distribution of sugar beet pectin using size exclusion chromatography

Partially degraded sugar beet (Beta vulgaris) pectins were characterised in terms of galacturonic acid, neutral sugar and ferulic acids contents. It was shown that the total neutral sugar content is correlated with the ferulic acid content. One pectin (C) was further characterised by size exclusion chromatography coupled to refractive index and UV detectors (SEC-RI-UV). This gave the opportunity to estimate how the ferulic acid and neutral sugar contents changed with hydrodynamic radius. Pectin C was found to be heterogeneous in composition with neutral sugar-rich fractions of both high and low hydrodynamic radii. A neutral sugar-poor fraction was found at intermediate hydrodynamic radii.

Comparisons between conventional, microwave- and ultrasound-assisted methods for extraction of pectin from grapefruit

Microwave-assisted Extraction (MAE) and Ultrasound-assisted extraction (UAE) techniques have been employed as complementary methods to extract carbohydrates, polysaccharides and other functional compounds from vegetable sources. In this work, the effect of microwave power and heating time on the yield and quality of extracted pectin from grapefruit was investigated. The highest total amount of pectin yield was found to be 27.81% (w/w) for 6 min of extraction at 900 W. It was observed that yield, the galacturonic acid content (GalA), and degree of esterification (DE) increased with an increase in microwave power and heating time. Besides, the molecular weight decreased with an increase in heating time; however, the effects of power on the molecular weight were dramatically more than heating time. In addition, laboratory studies on the extraction of pectin treated with high-intensity ultrasound were carried out. The effects of temperature and time on quality and quantity of extracted pectin were investigated. The highest yield was for sonication time of 25 min (17.92%) in a constant bath temperature of 70 °C. Furthermore, a preliminary ultrasonic heating of grapefruit solution, as a pretreatment for MAE, was found to provide a higher yield. Intermittent sonication gave better results in comparison to the continuous sonication.

Developmental Localization and Methylesterification of Pectin Epitopes during Somatic Embryogenesis of Banana (Musa spp. AAA)

BackgroundThe plant cell walls play an important role in somatic embryogenesis and plant development. Pectins are major chemical components of primary cell walls while homogalacturonan (HG) is the most abundant pectin polysaccharide. Developmental regulation of HG methyl-esterification degree is important for cell adhesion, division and expansion, and in general for proper organ and plant development.Methodology/Principal FindingsDevelopmental localization of pectic homogalacturonan (HG) epitopes and the (1→4)-β-D-galactan epitope of rhamnogalacturonan I (RG-I) and degree of pectin methyl-esterification (DM) were studied during somatic embryogenesis of banana (Musa spp. AAA). Histological analysis documented all major developmental stages including embryogenic cells (ECs), pre-globular, globular, pear-shaped and cotyledonary somatic embryos. Histochemical staining of extracellularly secreted pectins with ruthenium red showed the most intense staining at the surface of pre-globular, globular and pear-shaped somatic embryos. Biochemical analysis revealed developmental regulation of galacturonic acid content and DM in diverse embryogenic stages. Immunodots and immunolabeling on tissue sections revealed developmental regulation of highly methyl-esterified HG epitopes recognized by JIM7 and LM20 antibodies during somatic embryogenesis. Cell walls of pre-globular/globular and late-stage embryos contained both low methyl-esterified HG epitopes as well as partially and highly methyl-esterified ones. Extracellular matrix which covered surface of early developing embryos contained pectin epitopes recognized by 2F4, LM18, JIM5, JIM7 and LM5 antibodies. De-esterification of cell wall pectins by NaOH caused a decrease or an elimination of immunolabeling in the case of highly methyl-esterified HG epitopes. However, immunolabeling of some low methyl-esterified epitopes appeared stronger after this base treatment.Conclusions/SignificanceThese data suggest that both low- and highly-methyl-esterified HG epitopes are developmentally regulated in diverse embryogenic stages during somatic embryogenesis. This study provides new information about pectin composition, HG methyl-esterification and developmental localization of pectin epitopes during somatic embryogenesis of banana.

Extraction, characterization and spontaneous gel-forming property of pectin from creeping fig (Ficus pumila Linn.) seeds

Creeping fig (Ficus pumila Linn.) seeds can be manually rubbed and squeezed to produce a water extract (WE) that can gel at room temperature without any additives. Its gelling material, extraction behavior, and mechanism of spontaneous gel-formation were investigated. Gelling material was extracted from seeds using water, ammonium oxalate and hydrochloric acid, respectively. Results showed the main component of three extracts is low methoxyl pectin. The pectin locates in a transparent layer on the surface of seeds, as revealed by an inverted microscope. Hence, explained the feasibility of the squeezing and rubbing method in traditional handcraft. Comparing with the other methods, water-extracted pectin has high galacturonic acid content, viscosity-average molecular weight and intrinsic viscosity but low degree of methoxylation. This pectin forms the major component of WE, together with the high amount of calcium ions present in WE, it suggests the spontaneous gelation may be based on the ‘egg-box’ formation.

A Two-Step Chemical Process for the Extraction of Cellulose Fiber and Pectin from Mulberry Branch Bark Efficiently

In this work, a two-step method for the extraction of pectin and cellulose fiber from mulberry branch bark, a by-product of sericultural industry, was described. The method was based on the acid extraction of pectin and subsequently alkali treatment for obtaining cellulose fibers. The obtained pectin was high purity with the total galacturonic acid content of 85.46% ± 2.76% and the degree of esterification of 71.13% ± 1.67%. The chemical composition analysis, FTIR spectroscopy, XRD and TG analysis were used to characterize the cellulose fiber at different processing stages. After the two-step chemical process, the cellulose content was increased from 37.38% in original bark to 92.60% in cellulose fiber. The FTIR spectra revealed the removal of pectin, hemicelluloses and lignin from the bark by acid extraction and alkali treatment. The XRD and TG results indicated that the obtained cellulose fibers were with the increased crystallinity and thermal stability, whose crystallinity and degradation temperature were 86.36% ± 5.56% and 355 °C, respectively. This work may provide a new approach for high utilization of mulberry branch bark.

Novel source of pectin from young sugar palm by microwave assisted extraction

In this work, pectin extraction was performed using ripened sugar palm meat and young sugar palm meat as raw materials. The effect of extraction temperature and pH on the yield of pectin was investigated. It was found that the degree of esterification and galacturonic acid content decreased at high pH condition. The ripened sugar palm could give pectin as high as 20% yield at extraction condition of pH 2, 80°C, while the young sugar palm gave only 8.1% yield at pH 3. It was found that the adjustment of pH before and after extraction largely affected the yield of extraction. On the other hand, the extraction of young sugar palm meat at microwave power 800W at pH 2 with 3minutes of duration yielded as high as 23.5% of pectin. The results suggested that sugar palm meat had high potential as a new pectin source.

A new method for quantitative determination of two uronic acids by CZE with direct UV detection

A new method using capillary zone electrophoresis was developed for the rapid quantification of two common uronic acids, galacturonic acid and glucuronic acid, based on utilization of an alkaline background electrolyte with reversed electroosmotic flow (EOF) within 16 min. The method relies on in-capillary reaction and direct UV detection at the wavelength 270 nm. The optimum electrolyte solution was prepared of 130 mm sodium hydroxide, 36 mm disodium hydrogen phosphate dihydrate and 0.5 mm cetyltrimethylammonium bromide. EOF was reversed to detect uronic acids and to improve the separation of neutral sugars. The established method was validated and the results showed good linearity, high precision and satisfactory sensitivity. The newly developed method was successfully applied to analyze galacturonic acid and glucuronic acid content in Forsythia suspensa polysaccharides. The method is fast since only sample hydrolysis and dilution are required in the sample preparation.

Determination of galacturonic acid content in pectin from fruit juices by liquid chromatographydiode array detection-electrospray ionization tandem mass spectrometry

Abstract A reversed-phase high-performance liquid chromatographic (HPLC) method is applied for the determination of galacturonic acid (GA) of pectins in different commercial fruit juices. The separation was carried out on a C18 column using precolumn derivatization with p-aminobenzoic acid (p-ABA) and UV detection at 304 nm. The identification of GA was confirmed by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) in positive ion mode. The concentration of GA in the samples analyzed ranged from 12.9 ± 0.5 to 49.4 ± 0.5 mgGA L−1. Amongst the samples analyzed, mango juice was found to be richest in GA content, and therefore a good source of pectins. Detection and quantification limits of the described methodology were 1.2 and 3.9 mg L−1, respectively. Quantitative GA recoveries in the beverages had a range between 90 and 98%. The results showed that the HPLC method proposed was precise and suitable for the identification and quantification of GA in commercial fruit juices.

The relationship between dose-dependent antitussive and bronchodilatory effects of Opilia celtidifolia polysaccharide and nitric oxide in guinea pigs

A crude polysaccharide composed of uronic acids (32%), arabinose (26%), glucose (15%), galactose (11%), rhamnose (7%), mannose (5%), xylose (4%) and small amount of fucose residues has been isolated from the leaves of Opilia celtidifolia by boiled water extraction. Chemical analyses of Opilia polysaccharide revealed the prevalence of a pectin material with high arabinose and galacturonic acid contents. Opilia polysaccharide showed significant biological effects on chemically induced cough reflex and reactivity of airways smooth muscle in vitro and in vivo conditions in guinea pigs test system. Tests confirmed the dose-dependent cough-suppressive effect of Opilia polysaccharide comparable with activity of centrally acting codeine. Further, the bronchodilatory tests resulted in significant decrease in the values of specific airway resistance, which is very sensitive predictor of airway smooth muscle reactivity in vivo conditions regardless of bronchoconstricting mechanism. The results of in vitro experiments confirmed not only the bronchodilatory effect Opilia polysaccharide but revealed that its bronchodilatory mechanism is partially accompanied with enhanced NO production.

Structural characterization of polysaccharides from Zizyphus jujuba and evaluation of antioxidant activity

Fruit of Zizyphus jujuba Mill, a traditional Chinese herb widely consumed in Asian countries, has been reported to possess several vital biological activities. This study intends to develop an appropriate analytical method for isolation of polysaccharides from Z. jujuba fruits and evaluate their antioxidant activity. Initially, powdered Z. jujuba fruits were subjected to hot water extraction, followed by ethanol precipitation, deproteination, dialysis and fractionation in a DEAE-Sepharose CL-6B column. One neutral polysaccharide fraction (ZJPN) and 3 acidic polysaccharide fractions (ZJPa1, ZJPa2 and ZJPa3) were isolated with the average MW ranging from 40,566 to 129,518 Da. GC analysis revealed that 6 monosaccharides, namely, rhamnose, arabinose, xylose, mannose, glucose and galactose were present in polysaccharide fractions. The galacturonic acid content in polysaccharide fractions followed the order: ZJPa3 > ZJPa2 > ZJPa1 > ZJPN. All the 4 polysaccharide fractions were found to be more effective in scavenging superoxide anions than hydroxyl radicals, while acidic polysaccharides showed a more pronounced effect in chelating ferrous ion.

Composition and properties of biologically active pectic polysaccharides from leek (Allium porrum)

Leek (Allium porrum) is very commonly used vegetable in Bulgaria and is distinctive with high content of bioactive components. Previously we obtained five crude pectic polysaccharides from leek through consecutive extraction. Some of them appeared to be good stimulators of the immune system. Schols and Voragen investigated the composition of modified hairy regions of pectic polysaccharides isolated from leek cell walls. Samuelson et al. identified the polysaccharide structures encountered in hairy regions as bioactive. The aim of this work was to study the isolation, composition and biological activities of pectic polysaccharides from leek. Two pectic polysaccharides from leek were isolated through consecutive water and acid extraction. The water extractable pectin had higher polyuronic content, higher protein content and lower neutral sugar content. It was found that next to galacturonic acid they also contain glucuronic acid in ratio 9:1 for the water- and 3:1 for the acid-extractable polysaccharide. The main neutral sugar was galactose. The water-extractable pectic polysaccharide had higher molecular weight (10(6) Da) and homogeneity. It was shown that the pectic polysaccharides from leek have considerable immunostimulating activities. Leek polysaccharides have relatively high galacturonic and glucuronic acid content and are distinguished with high biological activity.