Abstract
BackgroundThe myxomycetes derive their common name (slime molds) from the multinucleate trophic stage (plasmodium) in the life cycle, which typically produces a noticeable amount of slimy materials, some of which is normally left behind as a “slime track” as the plasmodium migrates over the surface of a particular substrate. The study reported herein apparently represents the first attempt to investigate the chemical composition and biological activities of slime tracks and the exopolysaccharides (EPS) which cover the surface of the plasmodia of Physarum polycephalum and Physarella oblonga.ResultsChemical analyses indicated that the slime tracks and samples of the EPS consist largely of carbohydrates, proteins and various sulphate groups. Galactose, glucose and rhamnose are the monomers of the cabohydrates present. The slime tracks of both species and the EPS of Phy. oblonga contained rhamnose, but the EPS of Ph. polycephalum had glucose as the major monomer. In term of biological activities, the slime tracks displayed no antimicrobial activity, low anticancer activity and only moderate antioxidant activity. However, EPSs from both species showed remarkable antimicrobial activities, especially toward Candida albicans (zone of inhibition ≥20 mm). Minimum inhibitory concentrations of this fungus were found to be 2560 μg/mL and 1280 μg/mL for EPS from Phy. oblonga and Ph. polycephalum, respectively. These EPS samples also showed moderate antioxidant activities. However, they both displayed cytotoxicity towards MCF-7 and HepG2 cancer cells. Notably, EPS isolated from the plasmodium of Phy. oblonga inhibited the cell growth of MCF-7 and HepG2 at the half inhibitory concentration (IC50) of 1.22 and 1.11 mg/mL, respectively.ConclusionsEPS from Ph. polycephalum plasmodium could be a potential source of antifungal compounds, and EPS from Phy. oblonga could be a potential source of anticancer compounds.
Highlights
The myxomycetes derive their common name from the multinucleate trophic stage in the life cycle, which typically produces a noticeable amount of slimy materials, some of which is normally left behind as a “slime track” as the plasmodium migrates over the surface of a particular substrate
EPS production of Phy. oblonga and Ph. polycephalum The medium used for cultivation of myxomycete plasmodia was adapted from the research of Henney and Henney [23]
For slime track and EPS production, typical plasmodia of Ph. polycephalum and Phy. oblonga were transferred to nutrient and water agar, respectively, and incubated under dark condition at 25 °C for 7 days (Fig 1)
Summary
The myxomycetes derive their common name (slime molds) from the multinucleate trophic stage (plasmodium) in the life cycle, which typically produces a noticeable amount of slimy materials, some of which is normally left behind as a “slime track” as the plasmodium migrates over the surface of a particular substrate. The study reported apparently represents the first attempt to investigate the chemical composition and biological activities of slime tracks and the exopolysaccharides (EPS) which cover the surface of the plasmodia of Physarum polycephalum and Physarella oblonga. Microbial EPSs have gained a great deal of interest due to their potential biological activities [2]. EPSs isolated from bacteria and fungi have been found to possess inhibitory activities against gram positive and negative bacteria and the H1N1 virus [3,4,5]. Osama et al [5] found that EPS isolated from Bacillus marinus showed a strong antitumor property against breast cancer (MCF-7) cell lines and alveolar basal epithelia (A-549) cell lines at concentration of 100 μg/mL. EPS from Aspergillus aculeatus displayed a strong anti-proliferation effect on human cervical carcinoma cells (Hela), human breast carcinoma cells (MCF-7) and gastric carcinoma cells (MGC-803) with inhibition rates of 53.9%, 29.1% and 34.1%, respectively, at a concentration of 1000 μg/ mL for 48 h [10]
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