In this study, the physico-chemical characteristics of extracellular polysaccharides (EPS) produced by Arthrospira platensis were evaluated. Elemental analysis and a bicinchoninic acid (BCA) reaction indicated that the EPS were heteropolysaccharides that contain carbohydrate (13%) and protein (55%) moieties. Analysis of the infrared spectrum and elemental analysis revealed the presence of a sulfate group (0.5%). The UV-visible spectrum showed high UV absorption at 190~230 nm and a shoulder at 260~280 nm. In addition, this spectrum indicated that EPS can form aggregates with mycosporine-like amino acids and/or scytonemin. Gas chromatography analysis of the carbohydrate portion of the EPS indicated that it was composed of seven neutral sugars: galactose (14.9%), xylose (14.3%), glucose (13.2%), frucose (13.2%), rhamnose (3.7%), arabinose (1%), and mannose (0.3%) and two uronic acids, galacturonic acid (13.5%) and glucuronic acid (0.9%). © KSBB

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Water-soluble polysaccharides were isolated from Mesembryanthemumcrystallinum. Two methods were applied, based (i) on the extraction in hot water (for fresh and dry plants, FP and DP) and (ii) on freeze-thawing of fresh plants (FT). Each fraction was purified by precipitation in ethanol followed by ultrafiltration of recovered solids dissolved in water through a membrane with a molecular weight cut off of 100 000. Elemental analysis demonstrated that the extracted products were polysaccharides exempt from proteins. The yield relative to the corresponding dry matter varied from 1.6 to 3% depending on the starting sample and the extraction process. Obtained products were characterised by their structural (sugar composition, degree of methylation (DM) and acetylation, molar mass of acid equivalent unit) and macromolecular characteristics (molar mass and intrinsic viscosity). A galacturonic-acid content larger than 65% and a DM value of c. 40% showed that the isolated polysaccharides belong to the fairly methylated pectin class. FP and FT structures consisted of the two blocks homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) with relative proportions of 62 - 68% and 29 - 34%, respectively. They showed very similar physicochemical behaviour. On the other hand, DP exhibited significant differences in the chemical structure (50% HG and 46% RG-I blocks) and physical properties, indicating that partial degradation of HG moieties occurred during plant drying.

Bacterial secondary metabolites are a valuable source of various molecules that have antibacterial and anticancer activity. In this study, ten endosymbiotic bacteria of aphids, aphid predators and ants were isolated. Bacterial strains were identified according to the 16S rRNA gene. Ethyl acetate fractions of methanol extract (EA-ME) were prepared from each isolated bacterium and tested for their antibacterial activities using the disk diffusion method. The EA-ME of three bacterial species, Planococcus sp., Klebsiella aerogenes, Enterococcus avium, from the pomegranate aphids Aphis punicae, Chrysoperia carnea, and Tapinoma magnum, respectively, exhibited elevated antibacterial activity against one or several of the five pathogenic bacteria tested. The inhibition zones ranged from 10.00 ± 0.13 to 20.00 ± 1.11 mm, with minimum inhibitory concentration (MIC) values ranging from 0.156 mg/mL to 1.25 mg/mL. The most notable antibacterial activity was found in the EA-ME of K. aerogenes against Klebsiella pneumonia and Escherichia coli, with an MIC value of 0.156 mg/mL. The cytotoxic activity of EA-ME was dependent on the cell line tested. The most significant cytotoxicity effect was observed for extracts of K. aerogenes and E. avium, at 12.5 µg/mL, against the epithelial cells of lung carcinoma (A549), with a cell reduction of 79.4% and 67.2%, respectively. For the EA-ME of K. aerogenes and Pantoea agglomerans at 12.5 µg/mL, 69.4% and 67.8% cell reduction were observed against human colon cancer (Hct116), respectively. Gas chromatography–mass spectrometry (GC-MS) analysis of three EA-ME revealed the presence of several bioactive secondary metabolites that have been reported previously to possess antibacterial and anticancer properties. To the best of our knowledge, this is the first study to examine the biological activities of endosymbiotic bacteria in aphids, aphid predators and ants. The promising data presented in this study may pave the way for alternative drugs to overcome the continued emergence of multidrug-resistant bacteria, and find alternative drugs to conventional cancer therapies.