The phytoplankton diversity, algal biomass, and selected physicochemical parameters were investigated in the drinking water reservoir (Borovitsa) located in the Kardzhali region, Bulgaria. Particular attention was given to Cyanoprokaryota and presence of cyanotoxins in the water samples. Twenty-nine species belonging to six divisions (Cyanoprokaryota, Chlorophyta, Zygnemophyta, Dinophyta, Euglenophyta and Bacillariophyta) were identified. The microscopic examination of the phytoplankton samples showed the dominance of Ankyra judayi, Oocystis lacustris (Chlorophyta) and Aphanizomenon flos-aquae (Cyanoprokaryota) in July 2006, and Microcystis pulverea, Synechococcus elongatus (Cyanoprokaryota), Radiococcus planktonicus (Chlorophyta) and Melosira varians (Bacillariophyta) in September 2006. A blooming event due to Aphanizomenon flos-aquae was observed in July 2006. The reservoir exhibits a tendency to shift from an oligotrophic environment to a state of mesotrophy. Presence of cyanotoxins such as anatoxin-a, microcystins and saxitoxins were analyzed by HPLC and ELISA methods. Our results demonstrated the presence of anatoxin-a and microcystins (0.09 µg/L) in the raw water samples from July 2006, and saxitoxins (2.5 µg/L) and microcystins (0.18 µg/L) in the raw water samples from September 2006. The study underlines that permanent monitoring programs of Cyanoprokaryota in the reservoirs used as sources of drinking water and toxicity assessments should be implemented. Indirect exposure and transfer of cyanotoxins through food chains must also be considered.
Interest in plant extracts as a natural source of antioxidants has grown significantly in recent years. The tree species Koelreuteria paniculata deserves attention due to its wide distribution, good adaptability, and growth to the degree of invasiveness in a number of European countries. The purpose of the present study was to analyze flavonoids and phenolic acids of the ethanol extracts from aerial parts of K. paniculata and to screen their antioxidant and DNA-protective activity. HPLC profiling revealed the presence of five flavonoids, with rutin (4.23 mg/g DW), hesperidin (2.97 mg/g DW), and quercetin (2.66 mg/g DW) as the major ones in the leaves, and (−)-epicatechin (2.69 mg/g DW) in the flower buds. Among the nine phenolic acids identified, rosmarinic, p-coumaric, salicylic, vanillic, and gallic acids were the best represented. All the extracts tested showed in vitro antioxidant activity that was determined by DPPH, ABTS, FRAP, and CUPRAC assays. The highest activity was recorded in the flower parts (in the range from 1133 to 4308 mmol TE/g DW). The DNA-protective capacity of the flower and stem bark extracts from the in vitro nicking assay performed, as well as the main diagnostic microscopic features of the plant substances, are given for the first time. According to the results obtained, the aerial parts of K. paniculata could be valuable sources of natural antioxidants.
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