The polyphasic approach is the most progressive system that has been suggested for distinguishing and phylogenetically classifying Cyanoprokaryota (Cyanobacteria/Cyanophyta). Several oscillatorialean genera (Lyngbya, Phormidium, Plectonema, and Leptolyngbya) have problematic phylogenetic position and taxonomic state because of their heterogeneity and polyphyletic nature. To accurately resolve the phylogenetic relationship of some filamentous species (Nodosilinea bijugata, Phormidium molle, Phormidium papyraceum), we have performed phylogenetic analyses based on 16S rRNA gene and the phycocyanin operon (PC-IGS) by using maximum-likelihood (ML) tree inference methods. These analyses were combined with morphological re-evaluation. Our phylogenetic analyses support the taxonomic separation of genus Nodosilinea from the polyphyletic genus Leptolyngbya. Investigated Nodosilinea strains always formed a coherent genetic cluster supported with a high bootstrap value. The molecular phylogeny confirmed also the monophyly of the Wilmottia group. In addition, data reveal that although P. papyraceum is morphologically similar to Wilmottia murrayi, this species is genetically distinct. Strains from the newly formed genus Phormidesmis and some Phormidium priestleyi strains were clustered in a separate clade different from the typical Phormidium species, but without strong bootstrap support.

Until now, the interest to plants from genus Scutellaria in Bulgaria has been focused mainly on the terpenes in them. The purpose of this study is to enrich the information on the composition of the Bulgarian Scutellaria species in terms of both polyphenolic content as well as primary metabolites such as mono-, oligosaccharides and organic acids. An aerial part of three Scutellaria species growing in four low mountain regions of Southern Bulgaria was used. The flavonoids scutellarin, baicalin, baicalein, wogonin, wogonoside, luteolin, chrysin and a caffeoyl phenylethanoid glycoside-verbascoside have been identified via HPLC in different extracts from Scutellaria altissima, Scutellaria albida and Scutellaria galericulata. The antioxidant activity of the extracts has been evaluated. The Scutellaria altissima from Mezek and Scutellaria galericulata from Parvenets we studied, which are the richest in flavonoids (represented mainly by baicalin, scutellarin and wogonoside), show the highest Oxygen Radical Absorption Capacity. Hydroxyl Radical Averting Capacity of Scutellaria albida from Mezek and Scutellaria altissima from Bachkovo is the most pronounced, probably due to the content of scutellarin and luteolin and chrysin, respectively. Antioxidant activity of aqueous, methanolic and 70% and 96% ethanol extracts were also determined by the electrochemical method.

Cyanobacteria are unique prokaryotes, which are capable to perform oxygenic photosynthesis. Within these organisms, phycobilisomes (PBS) act as an antenna of the photosynthetic pigment apparatus. Phycobilisomes contain several phycobiliproteins (PBP): phycoerythrin (PE), phycocyanin (PC), allophycocyanin (APC) and phycoerythrocyanin (PEC). The application of phycobiliproteins in the biotechnology, food industry and medicine during the last years is rapidly increasing. The aim of our study was to assess the qualitative and quantitative content of phycoerythrin, phycocyanin, allophycocyanin and phycoerythrocyanin in 14 cyanobacterial strains kept in Plovdiv Algal Culture Collection (PACC) and 4 strains purchased from the Culture Collection of Autotrophic Organisms (CCALA). Our data demonstrated that three strains of Microcoleus autumnalis (PACC 5505, PACC 5522 and PACC 5527) have high potential to produce phycoerythrins (0.132, 0.201 and 0.136 mg/mL, respectively). Similarly, one Microcoleus autumnalis strain (PACC 5522) and one strain of Leptolyngbya boryana (CCALA 084) are suitable for biotechnological production of phycocyanins (0.051 and 0.264 mg/mL, respectively) as well as allophycocyanins (0.102 and 0.171 mg/mL, respectively). In addition, the data about the pigment content could be used as a biochemical marker for taxonomic purposes within the group.

Over the past decade new ecological indices based on phytoplankton and macrophytes were developed as part of the tools for assessment of the ecological status of water bodies. This study demonstrates the applicability of two of them (Assemblage index /Q/ and Algae Group Index /AGI/) for evaluation of water bodies from a lake type L4 as well as their comparability. Assessment of the ecological status of two lake ecosystems was performed in order to ensure successful protection, enhancement and management of lowland and semi-mountain lakes in Bulgaria. Data on the aquatic flora from Golyamo Skalensko Lake and Malko Skalensko Lake over a period of two years were used to assess their ecological status. In addition, the toxic potential of the established dominant cyanoprokaryotic species was also evaluated. Phytoplankton- and macrophyte-based metrics resulted in complementary evaluation of temporary and long-term environmental conditions. Despite the hydraulic connection and proximity between the two lakes, Golyamo Skalensko Lake and Malko Skalensko Lake appear as completely different ecosystems, according to the phytoplankton structure (species composition, number of species, abundance, seasonal succession), macrophytes and ecological status.

Betonica bulgarica is an endemic species distributed in Bulgaria. The chemical composition of the essential oil analysed by GC–MS (Gas chromatography–mass spectrometry) and the content of trace elements analysed by ICP–MS (Inductively coupled plasma mass spectrometry) were determined. Additionally, a study on the types and distribution of trichomes was done using a microscope with a camera. The essential oil was characterized using a high concentration of sesquiterpene hydrocarbons, whose major compounds are β-caryophyllene (17.4%), germacrene D (9.9%), and β-bourbonene (6.7%). The contents of manganese (177.2 µg/g) and strontium (156.8 µg/g) were highest among the investigated micronutrients. Two types of trichomes were identified on the adaxial and abaxial epidermises of the leaves of B. bulgarica—covering and glandular. Peltate stacked glandular trichomes with a four-celled head of type B were observed on the leaf surface.

Cyanobacteria are prokaryotic organisms characterized by their ability to produce secondary metabolites with different biological activities. The aim of this work was to evaluate the in vitro and in vivo toxicity of the cosmopolitan freshwater cyanobacterium H. kuetzingii. An extract from H. kuetzingii and cyanobacterial growth media were assessed for presence of intracellular and extracellular toxins by in vitro tests using primary cell cultures from mouse kidney and fibroblasts, cell lines A549 and 3T3, a fish cell line RTgill-W1 as well as by a traditional in vivo mouse bioassay. The presence of toxicity was compared with the ELISA and HPLC data for corresponding cyanotoxins. In vitro tests showed pronounced cytotoxicity of the cyanobacterium extract and growth medium in which H. kuetzingii released potential extracellular toxic compounds as the mammalian cells were significantly more sensitive to exposure compared to the fish cells. Histopathological analyses of the liver and kidneys of treated mice showed pathological changes such as leukocyte infiltration and necrosis, changes in the proximal and distal convoluted tubules, lack of differentiation of Bowman's space, enlarged Bowman's capsules and massive hemorrhages. ELISA and HPLC analyses confirmed the presence of saxitoxins and microcystins at low concentrations. In addition, the histological analyses suggest that H. kuetzingii produces other, yet unknown toxic metabolites. Monitoring efforts are therefore required to evaluate the potential hazard for the freshwater aquatic systems and possible public health implications associated with this cyanobacterium.

As producers of biomass, cyanobacteria are a major part of the phytoplankton in a large number of water basins. Due to the cyanobacterial blooms and cyanotoxins produced, these organisms are recognized as a threat and ecological risk for water bodies. Released cyanotoxins may cause death of many organisms including birds and fish. Vaya Lake is the largest natural lake in Bulgaria. It is located on the Via Pontica migration route of birds between Europe and Africa. Since 2003, the lake has been declared as a "Wetland of international importance” under the Ramsar Convention. According to the literature data from 2002-2006, the Lake is defined as highly eutrophied due to strong anthropogenic pressure, but regular monitoring of the cyanobacterial blooms and presence of cyanotoxins after this period is missing. Taking into account the importance of this unique, protected ecosystem, our aim was to make a complete ecological assessment of the present state of Lake Vaya by using the phytoplankton, with an emphasis on cyanobacterial blooms and the presence of cyanotoxins. As results of the study, we 1) characterized the phytoplankton composition qualitatively and quantitatively; 2) evaluated the ecological status of the western and eastern part of the Lake; 3) identified the potential producers of cyanotoxins; 4) observed cyanobacterial blooms and discussed the influence of macrophytes on their spread; 5) measured the concentrations of the cyanotoxins MCs, CYL and STXs in water samples from both parts of the Lake. Our results indicated the need for continued observation of cyanobacterial composition, blooming and the presence of cyanotoxins in Lake Vaya.

A normal-phase High Performance Liquid Chromatography (HPLC) method was developed for the determination of dehydroepiandrosterone (DHEA) in food supplements. We have used an HPLC 200 (Perkin Elmer, USA) with a spectrophotometric detector LC-785A (Bioanalytical systems, USA) and a thermostat (Perkin Elmer, Waltham, MA, USA). We have chosen isocratic HPLC elution, column: LiChrospher (100 DIOL 250 x 4 mm х 5 µm), mobile phase: acetonitrile: water = 98: 2 v/v, flow rate: 1 ml/min. and detection at λ = 202 nm. We have found that this method allows fast and selective qualitative and quantitative determination of DHEA in pharmaceutical products.