Gerald Blunden

Biological effects of gum arabic: a review of some recent research.

Gum arabic (GA) is a branched-chain, complex polysaccharide, either neutral or slightly acidic, found as a mixed calcium, magnesium and potassium salt of a polysaccharidic acid. The backbone is composed of 1,3-linked beta-D-galactopyranosyl units. The side chains are composed of two to five 1,3-linked beta-D-galactopyranosyl units, joined to the main chain by 1,6-linkages. Pharmacologically, GA has been claimed to act as an anti-oxidant, and to protect against experimental hepatic-, renal- and cardiac toxicities in rats. These reports could not be confirmed by others. GA has been claimed to alleviate the adverse effects of chronic renal failure in humans. This could not be corroborated experimentally in rats. Reports on the effects of GA on lipid metabolism in humans and rats are at variance, but mostly suggest that GA ingestion can reduce plasma cholesterol concentrations in rats. GA has proabsorptive properties and can be used in diarrhoea. It enhances dental remineralization, and has some antimicrobial activity, suggesting a possible use in dentistry. GA has been shown to have an adverse effect on electrolyte balance and vitamin D in mice, and to cause hypersensitivity in humans. More studies are needed before the pharmacological properties of GA can be utilized in therapy.

Enhanced leaf chlorophyll levels in plants treated with seaweed extract

Application to the soil of an aqueous alkaline extract ofAscophyllum nodosum resulted in higher concentrations of chlorophyll in the leaves of treated plants in comparison to control plants treated with an equivalent volume of water. Positive results were obtained with all species tested (tomato, dwarf French bean, wheat, barley, maize). When the seaweed extract was applied as a foliar spray, similar effects on leaf chlorophyll contents were obtained, except in the case of dwarf French bean plants, for which no significant difference was recorded between test and control plants. When the betaines present in the seaweed extract were applied as a mixture in the same concentrations as those in the diluted seaweed extract (γ-aminobutyric acid betaine 0.96 mg L−1, δ-aminovaleric acid betaine 0.43 mg L−1, glycinebetaine 0.34 mg L−1), very similar leaf chlorophyll levels were recorded for the seaweed extract and betaine treated plants. This suggests strongly that the enhanced leaf chlorophyll content of plants treated with seaweed extract is dependent on the betaines present.

Significance of betaines in the increased chlorophyll content of plants treated with seaweed extract

Seaweed extract, prepared by alkaline extraction of Ascophyllum nodosum (L.) Le Jol., applied either to the soil or to the foliage of tomato plants, produced leaves with higher chlorophyll levels than those of control plants. The effects on leaf chlorophyll content were investigated using a cucumber bioassay procedure devised for cytokinins. The seaweed extract was shown to increase the chlorophyll levels of the cucumber cotyledons, but ‘peaks’ of activity were obtained when widely different concentrations were used. The possibility that these effects were the result of betaines present in the extract was considered. Glycinebetaine, γ-aminobutyric acid betaine and δ-aminovaleric acid betaine all produced significantly enhanced chlorophyll concentrations in the cotyledons. ‘Peaks’ of activity were observed for each betaine: for glycinebetaine at 10−6 and between 10−4 and 101 mg 1−1, for γ-aminobutyric acid betaine at 10−6, between 10−4 and 10−1, and 101 mg 1−1, and for δ-aminovaleric acid betaine between 10−5 and 101 mg 1−1. It was concluded that the effects of enhancing chlorophyll levels produced by the seaweed extract were due, at least in part, to betaines.

Betaines and tertiary sulphonium compounds from 62 species of marine algae

Abstract From all 62 species of marine algae studied, either betaines or a tertiary sulphonium analogue or a mixture of the two types of compounds were extracted. Thus from this and earlier studies it would appear that either one or both of these classes of compounds are a constant feature of marine algae. Some compounds, in particular glycinebetaine, γ-aminobutyric acid betaine, prolinebetaine and 3-dimethyl-sulphoniopropionate, have a common and widespread distribution, whereas other compounds, e.g. β-prolinebetaine, trans-4- hydroxy-β-prolinebetaine , N- acetyllamine , δ-aminovaleric acid betaine and α-alaninebetaine, appear to have a very restricted occurrence. From Ptilota serrata, γ-aminobutyric acid betaine, methyl ester, was isolated and characterized; this is the first record of this substance as a natural product. It was not detected in any of the other algae investigated. The yields of betaines and tertiary sulphonium compounds obtained by extraction of the algae were low, especially from the Phaeophyceae. Apart from Chaetomorpha capillaris, for which 2% (of dry weight) of glycinebetaine was recorded, the yield of the major betaine or tertiary sulphonium compound from the other species investigated was less than 1% (of dry weight) and frequently less than 0.1%. The similarity of the betaines and their tertiary sulphonium analogues found in different species of the same genus show that these compounds have taxonomic significance at the genetic level.

Experimental gentamicin nephrotoxicity and agents that modify it: a mini-review of recent research.

The aminoglycoside antibiotic gentamicin (GM) is still widely used against infections by Gram-positive and Gram-negative aerobic bacteria. Its therapeutic efficacy, however, is limited by renal impairment that occurs in up to 30% of treated patients. The drug may accumulate in epithelial tubular cells causing a range of effects starting with loss of the brush border in epithelial cells and ending in overt tubular necrosis, activation of apoptosis and massive proteolysis. GM also causes cell death by generation of free radicals, phospholipidosis, extracellular calcium-sensing receptor stimulation and energetic catastrophe, reduced renal blood flow and inflammation. Many drugs have been shown to either ameliorate or potentiate GM nephrotoxicity. This article aims at updating the literature that has been published in the past decade on the effects of agents that either ameliorate or augment the nephrotoxicity of this aminoglycoside. Notable among the new ameliorating procedures are gene therapy, such as intravenous cell therapy with serum amyloid A protein-programmed cells, and the use of some novel antioxidant agents and oils of natural origin. These include, for example, green tea, garlic saffron, grape seed extracts as well as sesame and oleanolic oils. Agents that may augment GM nephrotoxicity include indomethacin, cyclosporin, uric acid and the Ca(++) -channel blocker verapamil. Most of the nephroprotective agents mentioned here have not been tested in large controlled clinical trials. Because of their relative safety and effectiveness, antioxidant agents seem to be good candidates for testing in humans.

Antimycobacterial, antiprotozoal and cytotoxic potential of twenty-one brown algae (phaeophyceae) from British and Irish waters

In the continuation of our research on seaweeds, crude extracts of 21 brown algae collected from the south coast of England and the west coast of Ireland were screened for in vitro trypanocidal, leishmanicidal and antimycobacterial activities. Mammalian stages of a small set of parasitic protozoa; i.e. Trypanosoma brucei rhodesiense, T. cruzi and Leishmania donovani, and the tubercle bacillus Mycobacterium tuberculosis were used as test organisms. The extracts were also evaluated for selectivity by testing on a mammalian cell line (L6 cells). Only four extracts were moderately active against T. cruzi, whereas all algal extracts showed significant activity against T. brucei rhodesiense, with Halidrys siliquosa and Bifurcaria bifurcata (Sargassaceae) being the most potent (IC50 values 1.2 and 1.9 μg/mL). All algal extracts also displayed leishmanicidal activity, with H. siliquosa and B. bifurcata again being the most active (IC50s 6.4 and 8.6 μg/mL). When tested against M. tuberculosis, only the B. bifurcata extract was found to have some antitubercular potential (MIC value 64.0 μg/mL). Only three seaweed extracts, i.e. H. siliquosa, B. bifurcata and Cystoseira tamariscifolia showed some cytotoxicity. To our knowledge, this is the first study on the antiprotozoal and antimycobacterial activity of brown algae from British and Irish waters. Copyright

Extraction, Purification and Characterisation of Dragendorff-positive Compounds from Some British Marine Algae

Methods are described for the extraction and purification of quaternary ammonium compounds and other Dragendorff-positive substances from marine algae and their preliminary characterisation by thin-layer chromatography and electrophoresis. The distribution of these compounds in nine species of British marine algae has been studied. From Ulva rigida, 3-dimethylsulphoniopropionate has been isolated; the same compound was detected chromatographically in U. lactuca, Enteromorpha compressa and K intestinalis. From Cladophora rupestris and Spyridia filamentosa glycine betaine has been isolated; choline was detected also in the latter species. From Cystoseira baccata glycine betaine was isolated and the presence of both 0-alanine betaine and γ-butyrobetaine was suggested from thin-layer Chromatographie evidence. The same three betaines were detected chromatographically in extracts of both C. nodicaulis and C tamariscifolia.

The Characterisation and Quantitative Estimation of Betaines in Commercial Seaweed Extracts

Glycinebetaine, γ-aminobutyric acid betaine and δ-aminovaleric acid betaine have been isolated from four commercially-produced seaweed extracts. A reliable proton magnetic resonance spectroscopic assay method for the estimation of all three compounds has been developed. High performance liquid chromatography using low wavelength ultra-violet light detection was found to be unsuitable for the analysis of betaines in seaweed extracts, even after partial purification by passage through columns of ion-exchange resin. A microbiological assay procedure was also utilised based on measuring the grov/th of Klebsiella pneumoniae produced by the addition of seaweed extracts to a medium with a growth-inhibitory concentration of sodium chloride. The concentrations of betaines found in the extracts when determined by the *H NMR spectroscopic method were too low to account for all of the anti-stress related effects reported for seaweed extracts after their application to plants. However, the microbiological assay results indicate that the extracts contain, in addition to betaines, other components which play a significant role in overcoming osmotically-induced growth Inhibition of K. pneumoniae.

Suppression of fecundity of the root-knot nematode, Meloidogyne javanica, in monoxenic cultures of Arabidopsis thaliana treated with an alkaline extract of Ascophyllum nodosum

Treatment of Arabidopsis thaliana plants with a commercially-available, alkaline extract of the marine brown alga, Ascophyllum nodosum, resulted in a significant decrease in the number of females of the root-knot nematode, Meloidogyne javanica, which developed in the roots compared to those of plants grown in a water control medium. Significant reductions in egg recovery were also achieved from plants treated with the seaweed extract. Similar effects were produced when betaine components of the seaweed extract (γ-aminobutyric acid betaine, δ-aminovaleric acid betaine and glycinebetaine) were used in quantities equivalent to those applied in the seaweed extract treatment. As the experiments were conducted under monoxenic conditions, it can be concluded that the results obtained with the application of either the seaweed extract or betaines are indicative of their effects on the plants and are not dependent on microorganisms associated with the rhizosphere.

Betaine distribution in the Amaranthaceae

Abstract Aerial parts of 23 species distributed in 10 genera of the Amaranthaceae have been examined for the presence of betaines. Glycinebetaine was isolated from all the species studied and, in addition, trigonelline was detected in eight out of the nine species of Amaranthus , 1 of the two species of Alternanthera and in the species of Iresine (3), Celosia (2), Chamissoa (1), Aerva (1), Gomphrena (1) and Froelichia (1). With the exception of I. herbstii , glycinebetaine was the predominant betaine. The highest yield of this compound was from Cyathula geniculata (2.11%, dry weight), but, with the exception of I. herbstii (0.05%), the species tested had contents in the range 0.28–2.11%, dry weight. Trigonelline yields varied from 0.004 to 0.15%, dry weight. From the data obtained, classification of the Amaranthaceae as a betaine – accumulating family would appear to be justified.