The dietary effects of gellan gum in humans

Molecular weight effects of low acyl gellan gum on antioxidant capacity and rheological properties

The current study investigated the antioxidant capacity of enzymatically cleaved low acyl gellan gum (LA-GAGR) fragments, named midi-GAGR (MW_v : 1.2 × 10⁵  Da) and mini-GAGR (MW_v : 2.5 × 10⁴  Da). Three different methods-hydroxide assay, superoxide assay, and DPPH assay-were used to measure the antioxidant capacity of the low acyl gellan gum fragments. Both mini-GAGR and midi-GAGR showed similar antioxidant capacities, 27.1% and 25.6%, respectively, for hydroxide radicals, whereas ascorbic acid showed 9.8%. For superoxide radicals, the fragments scavenged 41.7% (mini) and 35.6% (midi) of free radicals compared to 10.6% removal by ascorbic acid. Mini- and midi-GAGR displayed modest scavenging capabilities with DPPH radicals (8.5% and 6.6%, respectively) as compared to ascorbic acid (96.3%). Both midi- and mini-GAGR showed less gel-like behaviors than LA-GAGR. Midi-GAGR was observed to have a transition from liquid to gel at 63 rad/s. PRACTICAL APPLICATION: The results in the manuscript are helpful when gellan gum and its derivatives are directly applied to food processing as a dietary fiber supplement or a stabilizer for functional beverages. The antioxidant capacity results can be used to promote the functionality of gellan gum as a food additive and for controlling cell adhesion and growth on gellan gum scaffolds. The rheology results will be useful for synthesis of scaffolds for bone tissue generation and facilitating clinical treatments when gellan gum is injected as an adsorbent or a filler for treating bone fractures. In the pharmaceutical industry, they are useful when controlling the therapeutic effects of drug delivery systems.

Mini-GAGR, an intranasally applied polysaccharide, activates the neuronal Nrf2-mediated antioxidant defense system

Oxidative stress triggers and exacerbates neurodegeneration in Alzheimer's disease (AD). Various antioxidants reduce oxidative stress, but these agents have little efficacy due to poor blood-brain barrier (BBB) permeability. Additionally, single-modal antioxidants are easily overwhelmed by global oxidative stress. Activating nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2) and its downstream antioxidant system are considered very effective for reducing global oxidative stress. Thus far, only a few BBB-permeable agents activate the Nrf2-dependent antioxidant system. Here, we discovered a BBB-bypassing Nrf2-activating polysaccharide that may attenuate AD pathogenesis. Mini-GAGR, a 0.7-kDa cleavage product of low-acyl gellan gum, increased the levels and activities of Nrf2-dependent antioxidant enzymes, decreased reactive oxygen species (ROS) under oxidative stress in mouse cortical neurons, and robustly protected mitochondria from oxidative insults. Moreover, mini-GAGR increased the nuclear localization and transcriptional activity of Nrf2 similarly to known Nrf2 activators. Mechanistically, mini-GAGR increased the dissociation of Nrf2 from its inhibitor, Kelch-like ECH-associated protein 1 (Keap1), and induced phosphorylation and nuclear translocation of Nrf2 in a protein kinase C (PKC)- and fibroblast growth factor receptor (FGFR1)-dependent manner. Finally, 20-day intranasal treatment of 3xTg-AD mice with 100 nmol of mini-GAGR increased nuclear p-Nrf2 and growth-associated protein 43 (GAP43) levels in hippocampal neurons, reduced p-tau and β-amyloid (Aβ) peptide-stained neurons, and improved memory. The BBB-bypassing Nrf2-activating polysaccharide reported here may be effective in reducing oxidative stress and neurodegeneration in AD.

Role of process variables on the formation and in vitro digestion of gellan gels

Gellan gels were produced using different approaches forming structures with varied potential applications. Gels were characterized from appearance, mechanical properties, water holding capacity (WHC) and microstructure. In addition, in vitro digestibility of these gels was evaluated to understand the effect of gastrointestinal environment on their structure stability. All gels presented high WHC (>80% w/w) but gels were stronger with salt or acid addition, which was associated to the reduction of double helices repulsion of the negatively charged carboxyl groups of gellan. Moreover, low gelation rate induced a more controlled gellan helices aggregation, strengthening even more gels structure. Gellan gels presented resistance to digestion conditions but hardness of these gels during digestion mainly depended on the gelation rate. Based on these findings it would be possible to tune gel properties for a specific application as texture modifier or even as a faecal bulk formation assistant and an "ileal break" inducer.

Exopolysaccharide Gellan Gum and Derived Oligo-Gellan Enhance Growth and Antimicrobial Activity in Eucomis Plants

One of the visible trends in the cultivation of plants, particularly of medicinal ones, is the increasing interest of researchers in polysaccharides and their derivatives that show biostimulatory properties and are also safe to use. In the current study, we evaluated the effects of gellan gum and its depolymerized form oligo-gellan, on growth and antimicrobial activity of two ornamental species Eucomis bicolor and Eucomis comosa used in natural medicine. The biopolymers were applied in the form of bulb coating prepared by using polyelectrolyte complexes. In both species investigated, gellan gum and oligo-gellan enhanced the fresh weight of leaves and bulbs, the performance of the photosynthetic apparatus, and the leaf content of basic macronutrients. In comparison with the control, the plants treated with oligo-gellan accumulated more biomass, were first to flower, and had the highest leaf content of potassium. The extracts from the bulbs treated with gellan gum and oligo-gellan showed higher effectiveness in reducing the count of Bacillus atrophaeus, Escherichia coli, and Staphylococcus aureus than those from the bulbs not treated with the polysaccharides. The research described here largely expands our current knowledge on the effects of gellan gum derivatives and has a huge practical potential in agriculture production.

Safety Assessment of Microbial Polysaccharide Gums as Used in Cosmetics

The Cosmetic Ingredient Review Expert Panel assessed the safety of 34 microbial polysaccharide gums for use in cosmetics, finding that these ingredients are safe in cosmetic formulations in the present practices of use and concentration. The microbial polysaccharide gums named in this report have a variety of reported functions in cosmetics, including emulsion stabilizer, film former, binder, viscosity-increasing agent, and skin-conditioning agent. The Panel reviewed available animal and clinical data in making its determination of safety.

BBB-Permeable, Neuroprotective, and Neurotrophic Polysaccharide, Midi-GAGR

An enormous amount of efforts have been poured to find an effective therapeutic agent for the treatment of neurodegenerative diseases including Alzheimer’s disease (AD). Among those, neurotrophic peptides that regenerate neuronal structures and increase neuron survival show a promise in slowing neurodegeneration. However, the short plasma half-life and poor blood-brain-barrier (BBB)-permeability of neurotrophic peptides limit their in vivo efficacy. Thus, an alternative neurotrophic agent that has longer plasma half-life and better BBB-permeability has been sought for. Based on the recent findings of neuroprotective polysaccharides, we searched for a BBB-permeable neuroprotective polysaccharide among natural polysaccharides that are approved for human use. Then, we discovered midi-GAGR, a BBB-permeable, long plasma half-life, strong neuroprotective and neurotrophic polysaccharide. Midi-GAGR is a 4.7kD cleavage product of low acyl gellan gum that is approved by FDA for human use. Midi-GAGR protected rodent cortical neurons not only from the pathological concentrations of co-/post-treated free reactive radicals and Aβ₄₂ peptide but also from activated microglial cells. Moreover, midi-GAGR showed a good neurotrophic effect; it enhanced neurite outgrowth and increased phosphorylated cAMP-responsive element binding protein (pCREB) in the nuclei of primary cortical neurons. Furthermore, intra-nasally administered midi-GAGR penetrated the BBB and exerted its neurotrophic effect inside the brain for 24 h after one-time administration. Midi-GAGR appears to activate fibroblast growth factor receptor 1 (FGFR1) and its downstream neurotrophic signaling pathway for neuroprotection and CREB activation. Additionally, 14-day intranasal administration of midi-GAGR not only increased neuronal activity markers but also decreased hyperphosphorylated tau, a precursor of neurofibrillary tangle, in the brains of the AD mouse model, 3xTg-AD. Taken together, midi-GAGR with good BBB-permeability, long plasma half-life, and strong neuroprotective and neurotrophic effects has a great therapeutic potential for the treatment of neurodegenerative diseases, especially AD.

Subchronic (90-day) toxicity study in rats fed gum kondagogu (Cochlospermumgossypium)

Although gum kondagogu (Cochlospermum gossypium) is grouped under gum karaya (Sterculia sp.), it differs significantly in terms of physicochemical properties and chemical composition and does not conform to the confirmatory tests prescribed for gum karaya ([Janaki]). Gum karaya has wide applications in the pharmaceutical and food industries, whereas the use of gum kondagogu is yet to be explored. In this context, a short-term toxicity study on gum kondagogu was undertaken in rats. The gum was fed to rats at 0, 0.2%, 1% and 5% (w/w) in feed, for 90 days. Biochemical parameters were measured to assess the toxicity at the end of the study period. The results indicated no significant changes in growth pattern, haematological indices (RBC, WBC, Hb, PCV, MCV, MCH, MCHC, differential leucocyte counts), biochemical analytes (glucose, urea nitrogen, total protein, albumin, bilirubin, creatinine, sodium and potassium ions), activities of plasma and liver enzymes (alkaline phosphatase, alanine amino-transaminase, aspartate aminotransaminase, lactate dehydrogenase, glutathione S-transferase and gamma-glutamyl transpeptidases and organ to body mass ratio (brain, heart, lungs, liver, kidneys and spleen). Histopathology of the liver and kidney also did not reveal any abnormality. An increased faecal bulk was observed in rats fed with 5% gum kondagogu. However, faecal moisture content of female rats only was significantly different (P=<0.05) as compared to controls. Thus, it can be inferred, based on the present investigations, that gum kondagogu has a potential application as a food additive, similar to gum karaya. Feeding it at a much higher level (5%) than expected for consumption as a food additive also did not result in any toxic effect. Being non-toxic, gum kondagogu has a potential as a food additive with excellent physicochemical properties and a unique chemical composition.

Effect of the formulation on the in-vitro release of propranolol from gellan beads

Gellan gum beads of propranolol hydrochloride, a hydrophilic model drug, were prepared by solubilising the drug in a dispersion of gellan gum and then dropping the dispersion into calcium chloride solution. The droplets formed gelled beads instantaneously by ionotropic gelation. Major formulation and process variables which might influence the preparation of the beads and the drug release from gellan gum beads were studied. Very high entrapment efficiencies were obtained (92%) after modifying the pH of both the gellan gum dispersion and the calcium chloride solution. The beads could be stored for 3 weeks in a wet or dried state without modification of the drug release. Oven-dried beads released the drug somewhat more slowly than the wet or freeze-dried beads. The drug release from oven-dried beads was slightly affected by the pH of the dissolution medium. Gellan gum could be a useful carrier for the encapsulation of fragile drugs and provides new opportunities in the field of bioencapsulation.

Gellan in sustained release formulations: preparation of gel capsules and release studies

The ability of gellan to form gels in the presence of calcium ions enabled us to prepare capsules by gelation of this polysaccharide around a core containing starch, calcium chloride and a model drug. Release from the dried capsules was studied in vitro by means of the rotating basket technique (USP) in different environmental conditions (distilled water, pH = 2.0, pH = 6.8) and the effects of the presence of increasing amounts of drug in the formulation were also investigated. The behaviour of the gellan capsules was compared with that of beads prepared with the same polysaccharide but containing different additives. Results obtained indicate that gellan is suitable for the formulation of sustained release capsules and that solvent uptake by the dried capsules is most likely the main factor capable of affecting the rate of delivery from the tested preparations.

A follow-up study of the ingestion of gellan gum by humans, with special reference to the absence of eosinophilia

Following a 7-day control period, during which sampling was carried out on two occasions (days 1 and 8), 10 female and 10 male healthy volunteers consumed a weight of gellan gum corresponding to 175 mg/kg body weight for 7 days (days 8-14) followed by 200 mg gellan gum per kg body weight for a further 14 days (days 15-28). The total period of ingestion (21 days) was followed by a further 7-day control period (days 29-36). 'Control' samples for haematology and plasma clinical chemistry were therefore secured on days 1, 8 and 36, and 'test' samples were secured on days 15, 22 and 29. In addition, 24 h samples were monitored by urinalysis, and 24 h faecal samples were monitored for occult blood three times each week. The major objectives were to supplement the data for gellan gum obtained previously, particularly in respect of changes in eosinophil concentrations, and to re-examine the responses of two male volunteers who had given indications of eosinophilia in a previous study. There was no such response by them, or by any of the other 18 volunteers, on this occasion.

The effects of dietary methylcellulose in man

Following a 7-day control period, five male volunteers consumed, on each of 23 consecutive days, a weight of methylcellulose (MC) equal to ten times the acceptable daily intake (25 mg/kg b.w.) approved by the EEC and the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The MC was well tolerated; no allergic responses were reported. Measurements before and at the end of the test period showed that the ingestion of MC, as a pre-hydrated gel, acted as a bulking agent in terms of increased faecal wet (p less than 0.05) and dry weight, with intestinal transit time increasing for three but decreasing for two of the volunteers. Small changes, well within the normal ranges, occurred in some haematological indices, serum lipids and a few plasma biochemistry parameters. There were no changes in urinalysis parameters or breath hydrogen concentrations. There were small (p less than 0.05) reductions in faecal volatile fatty acids and neutral sterols (mumol/g dry weight). The decreases in blood glucose and plasma insulin after 60 min were also within the normal clinical range. The data provide no indications of any adverse effects of methylcellulose resulting from its ingestion for 23 days at the level of 250 mg/kg b.w.