Table 1.
Concentrations of naringenin in stock solutions and experimental media.
Fig 1.
Interdependence of the total chlorophyll content (μg mL-1) in day 7 (red) and day 14 (blue) cultures of halophilic and freshwater cyanobacteria and naringenin concentration, with the naringenin concentrations indicated on the appropriate radical axes (spider web graphs).
The axes indicated as “0” belong to the appropriate controls (cultures without naringenin). The points that indicate the contents of chlorophyll on the axes that indicate various concentrations of naringenin reflect a stimulatory effect when they are above the relevant value on axis “0”, whereas the points located below this value, reflect an inhibitory action. All values are the means from at least five independent experiments (n = 5). The significance of the influence of naringenin on chlorophyll content is shown in the form of asterisks (*p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001) was tested against appropriate controls.
Table 2.
The ratios of the growth rates of experimental cultures with respect to the growth rate of appropriate controls at certain concentrations of naringenin, expressed as percentage values ± s.d.
Fig 2.
The representative SEM photographs of Spirulina platensis (A), Spirulina platensis + N (naringenin) (100 mg L-1) (B), Anabaena laxa (C), Anabaena laxa + N (80 mg L-1) (D), Nodularia moravica (E), Nodularia moravica + N (80 mg L-1) (F) illustrate the differences in the structure of the cyanobacterial cell walls between the control and experimental cultures.
Fig 3.
The representative superimposed HPLC chromatograms of the substrate control containing 20 mg L-1 of naringenin in MSp or BG11 media and the experimental media of Arthrospira fusiformis, obtained at a wavelength of 290 nm.
The magnification window contains part of the superimposed chromatogram, which presents the measured intensity of the peak of naringenin detected in postharvest medium of A. fusiformis.
Fig 4.
A representative figure of different colours of the extracts of Anabaena sp. cell extracts: green-grey extract from cell biomass of control (C) and orange-green of the extract of the experimental culture supplemented with 20 mg L-1 of naringenin (A). The presence of two maxima (ca. 290 and ca. 330 nm) of absorption in the UV-VIS differential (“experiment” vs. “control”) spectra of the extracts from the cell biomass of Anabaena sp. treated with (A) 20 mg L-1 and (B) 60 mg L-1 of naringenin revealed the presence of this flavanone.
Fig 5.
The representative GC-FID superimposed chromatograms of the extracts from the cells of Anabaena sp. and from the substrate control.
The precise location and intensity of the peaks of the naringenin standard (A), natively produced undefined polyphenolic compound (C) and the substances extracted from the culture supplemented with naringenin (B) are present in the magnification window.