Plant type II arabinogalactan: Structural features and modification to increase functionality.

Type II arabinogalactans (AGs) are a highly diverse class of plant polysaccharides generally encountered as the carbohydrate moieties of certain extracellular proteoglycans, the so-called arabinogalactan-proteins (AGPs), which are found on plasma membranes and in cell walls. The basic structure of type II AG is a 1,3-ß-D-galactan main chain with 1,6-ß-D-galactan side chains. The side chains are further decorated with other sugars such as α-l-arabinose and ß-d-glucuronic acid. In addition, AGs with 1,6-ß-D-galactan as the main chain, which are designated as 'type II related AG' in this review, can also be found in several plants. Due to their diverse and heterogenous features, the determination of carbohydrate structures of type II and type II related AGs is not easy. On the other hand, these complex AGs are scientifically and commercially attractive materials whose structures can be modified by chemical and biochemical approaches for specific purposes. In the current review, what is known about the chemical structures of type II and type II related AGs from different plant sources is outlined. After that, structural analysis techniques are considered and compared. Finally, structural modifications that enhance or alter functionality are highlighted.

Chemically sulfated polysaccharides from natural sources: Assessment of extraction-sulfation efficiencies, structural features and antiviral activities.

The provisioning of compound libraries with a high degree of diversity and attractive pharmacological properties is a limiting step in drug development. This study reports the production of highly bioactive sulfated polysaccharides, originally present in a nonsulfated, dormant state in natural sources, and demonstrates their antiviral activity (human cytomegalovirus EC50 values of 2.34-7.77 µg/mL) at a low degree of cytotoxicity. Furthermore, data strongly suggested the inhibition of virus entry as the main mode of antiviral action. Remarkably, the utilized oleum-DMF reagent was able to generate a range of sulfated polysaccharides from various natural sources, possessing varying saccharide compositions, degrees of sulfation (0.4-1.7) and molecular masses (38-94,000 g/mol). Typically, in a matter of minutes, this reagent not only solubilized polysaccharides but also chemically converted their hydroxyl functionality into sulfates. The most active sulfated polysaccharide (EC50 of 2.62 µg/mL) proved to be a 94,000 g/mol branched glucan with sulfates at C-6/C-3,6/C-2,3,6 positions. In conclusion, the important determinants of such compounds' antiviral activity are: (i) degree of sulfation, (ii) molecular mass and (iii) structural features. Thus, our approach offers a huge prospect for the improvement of natural source-derived libraries based on biologically active polysaccharides with diversified chemical profiles.

Polysaccharides from Thymus vulgaris leaf: Structural features, antioxidant activity and interaction with bovine serum albumin.

Thymus vulgaris is used for various health benefits and culinary, nevertheless, report on its macromolecules is absent. Here, we report chemical compositions of the polysaccharides isolated from its leaf by sequential extraction with inorganic solvents. In particular, chemical profile of a unique rhamnogalacturonan I type polysaccharide containing ester linked phenolic acids has been described. Sugar compositional, TLC, UV-spectrometric and ESI-MS analyses of oligosaccharides generated from this polysaccharide by enzyme digestion, controlled acid hydrolysis and Smith degradation revealed atypical fine structural details. Biochemical analysis demonstrated dose-dependent antioxidant activity. A combination of large neutral side chains of the ramified region and ester linked phenolic acids are regarded as the functional sites. Ultraviolet spectrometric and fluorimetric analyses showed that this polysaccharide forms a homogeneous water-soluble complex with bovine serum albumin (binding constant, K = 2.91 × 106/M). Consequently, water extraction affords a polysaccharide which induces pharmacological effect; this underlines the impact of thyme as natural dietetic antioxidant.

In vivo cough suppressive activity of pectic polysaccharide with arabinogalactan type II side chains of Piper nigrum fruits and its synergistic effect with piperine.

Piper nigrum L. fruits are not only a prized spice, but also highly valued therapeutic agent that heals many ailments including asthma, cold and respiratory problems. Herein, we have investigated structural features and in vivo antitussive activity of three fractions isolated from Piper nigrum fruits. The water extract (PN-WE) upon fractionation with EtOH yielded two fractions: a soluble fraction (PN-eSf) and a precipitated (PN-ePf) one. The existence of a pectic polysaccharide with arabinogalactan type II side chains (147kDa) in PN-ePf and piperine in PN-eSf were revealed. Moreover, oligosaccharides providing fine structural details of side chains were generated from PN-ePf and then characterized. The parental water extract (PN-WE) that contained both pectic polysaccharide and piperine, after oral administration (50mgkg-1 body weight) to guinea pigs, showed antitussive activity comparable to codeine phosphate (10mgkg-1 body weight). The EtOH precipitated fraction (PN-ePf) containing pectic polysaccharide showed comparatively higher antitussive activity than EtOH soluble fraction (PN-eSf) that contained piperine, but their potencies are lower than the parental water extract. Significantly, the specific airway smooth muscle reactivity of all three fractions remained unchanged. Finally, pectic polysaccharide-piperine combination in parental extract synergistically enhances antitussive effect in guinea pigs.

Isolation and structural elements of a water-soluble free radical scavenger from Nyctanthes arbor-tristis leaves.

The leaves of Nyctanthes arbor-tristis L. (Oleaceae) are used in Ayurvedic medicine for the management of a range of diseases, but reports on its phytochemicals and pharmacological properties are inadequate. Herein, we report purification of an antioxidative polysaccharide (F2) extracted from its leaves by water. The presence of a highly branched polysaccharide (75 kDa) containing esterified phenolic acids was revealed by chemical, chromatographic and spectroscopic analyses. Particularly, ESMS analysis of per acetylated oligomeric fragments derived by Smith degradation provides important structural information on a spectrum of glycerol tagged oligosaccharides. This polysaccharide showed dose dependent free radical scavenging capacity as evidenced by DPPH and Ferric reducing power assay. This pharmacologically active compound (F2) formed a water soluble complex with bovine serum albumin over pH 4.0-7.4. Accordingly, traditional aqueous extraction method provides a molecular entity that induces a pharmacological effect: this could epitomize a smart approach in phytotherapeutic management.

Isolation and structural features of an antiradical polysaccharide of Capsicum annuum that interacts with BSA.

Red peppers, Capsicum annuum, are used worldwide as spices, foods and medicines. Herein, we have analyzed an antiradical polysaccharide isolated from red peppers through successive acetate buffer extraction. This macromolecule was purified using graded precipitation with ethanol, α-amylase treatment, deproteination and anion-exchange chromatography. This highly-branched polysaccharide (360 kDa) was esterified with phenolic acids and contained a (1,3)-linked-ß-Galp chain substituted at O-6 by (1,6)-linked-ß-Galp residues. The latter was substituted at O-3 by (1,5)- and (1,3,5)-linked-α-Araf residues, and non-reducing end-units of α-Araf and ß-Galp. The antiradical potential of this polysaccharide was comparable to standard antioxidants. The phenolic acid residues were the functional sites. This polysaccharide could form complex with bovine serum albumin having binding constant K = 5.24 × 10(6)/M and change its microenvironment. Thus, aqueous extraction method provides a macromolecule that stimulates biological responses; this emphasizes the significance of red pepper as dietary antioxidant.

Extracted polysaccharide from Nyctanthes arbor-tristis leaves: chemical and antitussive properties.

The prevalence of cough is reflected in antitussives being one of the most widely used therapies in the world; however no new class of drugs has been introduced into the market for many years. Water decoction of the leaves of Nyctanthes arbor-tristis L. is used in Indian Ayurvedic system to alleviate a wide range of diseases including cough. Herein, we have isolated a carbohydrate polymer (CP) containing fraction from its leaves by aqueous extraction method. CP is a branched polysaccharide containing, amongst others, 1,3-/1,3,6-linked galactopyranosyl, 1,5-/1,3,5-linked arabinofuranosyl and 1,2-/1,2,4-linked rhamnopyranosyl residues. Oral administration of CP fraction in doses of 25 and 50 mg kg(-1) body weight significantly inhibited the number of citric acid-induced cough efforts in guinea pigs in a dose dependent manner. Remarkably, CP did not altered specific airway resistance of animals significantly. Consequently, aqueous extraction method provided a molecular entity, which exhibited the cough suppressive activity: this could symbolize an attractive approach in phytotherapeutic treatment.

Chemical structure of the arabinogalactan protein from gum ghatti and its interaction with bovine serum albumin.

Exudate gums, because of their beneficial properties, have been significant items of international trade in various industries for centuries. This manuscript sets out to gain insight into the fine structural details of an arabinogalactan protein (AGP) of gum ghatti (Anogeissus latifolia gum). The presence of a highly branched 554 kDa AGP having 1,6-linked Galp, 1,2-linked Manp, 1,3-linked Araf and 1,4-linked GlcpA main chain, substituted at O-4,6 of 1,2-linked Manp, and O-3/O-3,4 of 1,6-linked Galp residues by Araf, Arap and Galp units was revealed by chemical, chromatographic, ESMS, and NMR analyses. In particular, ESMS analysis of per acetylated oligomeric fragments derived from AGP by Smith degradation followed by acetylation was described as a commanding tool for providing critical structural information on a spectrum of glycerol tagged oligosaccharides. In addition, formation of an electrostatically driven complex between the isolated AGP and bovine serum albumin resulting in changes in the microenvironment around the tryptophan residues of BSA was established. A moderate radical scavenging activity comparable with those of standard antioxidants was observed from the AGP fraction (∼94% at 1 mg/mL) that could be valuable in foods or pharmaceutical products as alternatives to synthetic antioxidants.

In vivo antitussive activity of a pectic arabinogalactan isolated from Solanum virginianum L. in Guinea pigs.

ETHNOPHARMACOLOGICAL RELEVANCE: Solanum virginianum L. is used for the management of fever, bronchial asthma and cough for thousands of years. While the link to a particular indication has been established in human, the active principle of the formulation remains unknown. Herein, we have investigated a polysaccharide isolated from its leaves. MATERIALS AND METHODS: Utilizing traditional aqueous extraction protocol and using chemical, chromatographic, spectroscopic and biological methods we have analysed an antitussive pectic arabinogalactan isolated from its leaves. RESULTS: The water extracted polymer (WEP) is a highly branched arabinogalactan containing, inter alia, (1,3)-, (1,6)- and (1,3,6)-linked ß-Galp residues, terminal-, (1,5)- and (1,3,5)-linked units of α-Araf together with (1,2)- and (1,2,4)-linked Rhap. In vivo investigation on the citric-acid induced cough efforts in guinea pigs shows that the antitussive activity of the orally administered pectic arabinogalactan is greater than codeine phosphate. Remarkably, this macromolecule neither altered specific airway smooth muscle reactivity significantly nor it induced considerable change on levels of NO in expiratory flow in guinea pigs. CONCLUSIONS: Thus, traditional aqueous extraction method provides a molecular entity, which induces antitussive activity without addiction: this could represent an attractive approach in phytotherapeutic management.

Antitussive arabinogalactan of Andrographis paniculata demonstrates synergistic effect with andrographolide.

Traditional Indian medicines have been used in humans for thousands of years. While the link to a particular indication has been established in man, the active principle of the formulations often remains unknown. In this study, we aim to investigate the structural features and antitussive activity of fractions from Andrographis paniculata leaves. In vivo investigations of water extract (WE), and both ethanol-soluble (WES) and precipitated (WEP) fractions from WE on the citric-acid induced cough efforts and airways smooth muscle reactivity in guinea pigs were performed. Chemical, chromatographic and spectroscopic analysis revealed the existence of a highly branched pectic arabinogalactan (109kDa) in WEP and andrographolide in WES. WEP showed significant antitussive activity while the potencies of WE and WES are even higher. Neither WE nor WES significantly alter specific airway smooth muscle reactivity. Remarkably, the antitussive activity of arabinogalactan could be increased by synergistic action with andrographolide. Finally, traditional aqueous extraction method provides an arabinogalactan from A. paniculata, which stimulate biological response but without addiction.

Interaction with bovine serum albumin of an anti-oxidative pectic arabinogalactan from Andrographis paniculata.

A pectic arabinogalactan was obtained from the leaves of Andrographis paniculata by aqueous extraction followed by α-amylase treatment, deproteination, and anion exchange chromatography. Methylation analysis, Smith degradation, and NMR spectroscopy indicated that it was a highly branched arabinogalactan containing a (1→3)-linked ß-d-Galp main chain, substituted at O-6 by (1→6)-linked ß-d-Galp side chains. The latter residues were substituted at O-3 by (1→5)- and (1→3)-linked α-l-Araf chains, and non reducing end-units of α-l-Araf and ß-d-Galp. This homogeneous arabinogalactan (36 kDa), which contained phenolic acids, showed dose-dependent anti-oxidative properties. The phenolic acid moieties might be the functional sites. This arabinogalactan can form a complex with bovine serum albumin having binding constant K=6.48 × 10(6)/M. Thus, this study is an important step forward to investigate the involvement of arabinogalactan in processes including interaction with biologically important transport proteins.

Chemically engineered sulfated glucans from rice bran exert strong antiviral activity at the stage of viral entry.

Attachment and entry of many viruses are mediated by their affinity for polysaccharides present on the surface of target cells. In this paper, we demonstrate that sulfated glucans isolated from rice (Oryza sativa) can be utilized as experimental drugs exerting strong antiviral activity. In particular, oleum-DMF-based extraction is described as a procedure for the generation of chemically engineered glucans from commercially available rice bran. The one-step procedure has the potential to provide a spectrum of related glucans with varying molecular masses and modifications, including sulfation. The sulfated glucans P444, P445, and P446 possess increased antiviral activity compared to a previously described glucan (S1G). P444, P445, and P446 were highly active against human cytomegalovirus (HCMV), moderately active against other members of the family Herpesviridae, while not active against unrelated viruses. Specific experimentation with HCMV-infected cells provided evidence that antiviral activity was based on inhibition of viral entry and that inhibition occurred in the absence of drug-induced cytotoxicity. These findings underline the high potential of sulfated glucans for antiviral research and drug development. In addition, the procedure described for the efficient transformation of glucan hydroxy groups to sulfate groups may be similarly beneficial for the chemical alteration of other natural products.

Antioxidative carbohydrate polymer from Enhydra fluctuans and its interaction with bovine serum albumin.

Enhydra fluctuans leaves are traditionally sold on Indian markets for various health benefits. However, no phytochemical study on its high molecular weight compound has so far been performed. Chemical, chromatographic, ESI-TOF-MS, and NMR analyses of the water extracted carbohydrate polymer (CP) of E. fluctuans leaves showed the presence of a 24 kDa arabinogalactan having a (1,3)-linked ß-d-Galp main chain, substituted at O-6 by (1,6)-linked ß-d-Galp side chains. The latter residues were substituted at O-3 by (1,3)-, (1,5)-, and (1,3,5)-linked α-l-Araf chains, and nonreducing end-units of α-l-Araf and ß-d-Galp. This polymer contained esterified phenolic acids. Biochemical analysis revealed similarity in antioxidative potential between the identified carbohydrate polymer and known standard antioxidants. The highly branched side chains and the phenolic acid residues of the arabinogalactan might be the functional sites. Fluorimetric and ultraviolet spectrometric analyses showed that the studied carbohydrate polymer can form complex with bovine serum albumin having binding constant K = 2.42 × 10(6)/M and changes its microenvironment. Thus, traditional aqueous extraction method provides a carbohydrate polymer, which stimulates a fair biological response: this could represent an interesting approach in phytotherapeutic treatments.