Plamena Staleva

Dr. Plamena Staleva

orcid

Research Focus & Metrics

Academic Career Length

8Years (2019-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
19 November 2023 in Molecules
Verified
Journal Article
Open access
PDF file
Antoaneta TrendafilovaAntoaneta Trendafilova
Antoaneta Trendafilova
PSPlamena Staleva
Plamena Staleva
ZPZhanina Stoyanova Petkova
Zhanina Stoyanova Petkova
VIViktoria Ivanova
Viktoria Ivanova
YEYana Evstatieva
Yana Evstatieva
SSSvetlana Simova
Svetlana Simova
Dry rose extract (DRE) obtained industrially by aqueous ethanol extraction from R. damascena flowers and its phenolic-enriched fraction, obtained by re-extraction with ethyl acetate (EAE) were the subject of this study. 1H NMR of DRE allowed the identification and quantitation of fructose and glucose, while the combined use of HPLC-DAD-ESIMS and HPLC-HRMS showed the presence of 14 kaempferol glycosides, 12 quercetin glycosides, 4 phenolic acids and their esters, 4 galloyl glycosides, 7 ellagitannins, and quinic acid. In addition, the structures of 13 of the flavonoid glycosides were further confirmed by NMR. EAE was found to be richer in TPC and TFC and showed better antioxidant activity (DPPH, ABTS, and FRAP) compared to DRE. Both extracts displayed significant activity against Propionibacterium acnes, Staphylococcus aureus, and S. epidermidis, but showed no activity against Candida albicans. Toxicity tests on normal human skin fibroblasts revealed low toxicity for both extracts with stronger effects observed at 24 hours of treatment that were compensated for over the following two days. Human hepatocarcinoma (HepG2) cells exhibited an opposite response after treatment with a concentration above 350 µg/mL for EAE and 500 µg/mL for DRE, showing increased toxicity after the third day of treatment. Lower concentrations were non-toxic and did not significantly affect the cell cycle parameters of either of the cell lines.

20 May 2019 in Chemistry – A European Journal
Verified
Journal Article
Closed access
PDF file
PSPlamena Staleva
Plamena Staleva
JHJosé G. Hernández
José G. Hernández
Carsten BolmCarsten Bolm
Carsten Bolm

21 February 2023 in Polymers
Verified
Journal Article
Open access
PDF file
NSNikoleta Stoyanova
Nikoleta Stoyanova
Maria SpasovaMaria Spasova
Maria Spasova
NMNevena Manolova
Nevena Manolova
IRIliya Rashkov
Iliya Rashkov
MKMariana Kamenova-Nacheva
Mariana Kamenova-Nacheva
MTMaya Tavlinova-Kirilova
Maya Tavlinova-Kirilova
In the present study, the plant extract Melissa officinalis (M. officinalis) was successfully loaded in polymer fibrous materials on the basis of a biodegradable polyester–poly(L-lactide) (PLA) and biocompatible polyether–polyethylene glycol (PEG) by applying the electrospinning method. The optimal process conditions for the preparation of hybrid fibrous materials were found. The extract concentration was varied—0, 5 or 10 wt% in respect of the polymer weight, in order to study its influence on the morphology and the physico-chemical properties of the obtained electrospun materials. All the prepared fibrous mats were composed of defect-free fibers. The mean fiber diameters of the PLA, PLA/M. officinalis (5 wt%) and PLA/M. officinalis (10 wt%) were 1370 ± 220 nm, 1398 ± 233 nm and 1506 ± 242 nm, respectively. The incorporation of the M. officinalis into the fibers resulted in slight increase of the fiber diameters and in increase of the water contact angle values to 133°. The presence of the polyether in the fabricated fibrous material assisted the wetting of the materials imparting them with hydrophilicity (the value of the water contact angle become 0°). Extract-containing fibrous materials displayed strong antioxidant activity as determined by the 2,2-diphenyl-1-picryl-hydrazyl-hydrate free radical method. The DPPH solution color changed to yellow and the absorbance of the DPPH radical dropped by 88.7% and 91% after being in contact with PLA/M. officinalis and PLA/PEG/M. officinalis mats, respectively. These features revealed the M. officinalis—containing fibrous biomaterials promising candidates for pharmaceutical, cosmetic and biomedical use.

10 February 2025 in Foods
Verified
Journal Article
Open access
PDF file
Zvezdelina YanevaZvezdelina Yaneva
Zvezdelina Yaneva
NGNeli Hristova Grozeva
Neli Hristova Grozeva
Mima TodorovaMima Todorova
Mima Todorova
MKMariana Kamenova-Nacheva
Mariana Kamenova-Nacheva
PSPlamena Staleva
Plamena Staleva
Milena Tankova TzanovaMilena Tankova Tzanova
Milena Tankova Tzanova
Alkanna tinctoria L. Tausch (“alkanet” or “alkanna”) is a medicinal plant. Extracts from alkanet roots have applications as natural food coloring agents. In addition, they have proven antioxidant effects. Three classical solvents (ethanol and acidified ethanol/water) and four natural eutectic solvents (NADES)—choline chloride/urea; choline chloride/citric acid; choline chloride/lactic acid; and sodium acetate/formic acid—were compared for their effectiveness as “green” solvents for the extraction of the alkanet pigment. Notably, this study is the first to apply choline chloride-based NADESs for alkanet extraction, providing a comprehensive profile of key bioactive compounds and their contributions to antioxidant activity using UV/Vis and FT-IR spectrometry, GC-MS, and HPLC-PDA-MS. Among the classical solvents, 50% acidified ethanol showed the highest extraction capacity, as indicated by its total flavonoid (708 ± 32 mgCE/L) and total phenolic (1318 ± 63 mgGAE/L) content. However, this extract exhibited the highest total alkaloid content (256 ± 15 µg/L) compared to the other classical extraction solvents. Consequently, absolute ethanol was identified as a more suitable alternative. Among the NADES, the sodium acetate/formic acid (1:2 mol/mol, NADES4) extract was the only one to show the presence of alkannins. This extract also contained high levels of phenols (355 ± 21 mg GAE/L) and tannins (163 ± 10 mg CE/L), exhibited strong antioxidant potential (DPPH: 131 µmol TE/g dw, FRAP: 7.49 mg Fe(II)/mg dw), and contained significantly lower alkaloid levels (7.0 ± 0.5 µg/L). Comparative analyses indicated that the sodium acetate/formic acid extract outperformed those prepared with ethanolic solvents and other NADES.

Verified
Journal Article
Open access
PDF file
PAPetya Angelova
Petya Angelova
АHАnton Hinkov
Аnton Hinkov
VDVanya Dimcheva
Vanya Dimcheva
PSPlamena Staleva
Plamena Staleva
MKMariana Kamenova-Nacheva
Mariana Kamenova-Nacheva
KSKalina Avgust Shishkova
Kalina Avgust Shishkova
Recently, previously known viruses have changed their pathogenicity and encompassed new types of host populations. An example of such an infection is that caused by SARS-CoV, belonging to the “well-known” coronavirus family. Another group of viruses that are of great importance to the human population are the herpes viruses. Due to increasing viral resistance to existing antiviral drugs, plant extracts are attracting increasing interest due to their complex composition and their simultaneous attack of different viral targets. Based on the above, we tested the antiviral potential of water–alcoholic extract obtained from a commercial sample of the plant Cistus incanus L. against the enveloped viruses SvHA1, SvHA2 (ACV resistant) and HCoV 229E. The results showed both complete inhibition of the intracellular stages of the viral replication and a strong effect on extracellular virions in the three viral models. In a study of the effect on the replication of SvHA 2, the calculated selectivity index was over 10. From the experiments on the virucidal effects on the two herpes viruses, it was found that the viral titer of the samples decreased by about 4 lg compared to the control sample. The extract is of interest for introduction into practice.

8 May 2026 in Molecules
Verified
Journal Article
Open access
PDF file
NMNeli Memdueva
Neli Memdueva
Milena Tankova TzanovaMilena Tankova Tzanova
Milena Tankova Tzanova
PSPlamena Staleva
Plamena Staleva
MKMariana Kamenova-Nacheva
Mariana Kamenova-Nacheva
KKKalina Krastilova
Kalina Krastilova
TDToncho Dinev
Toncho Dinev
Due to its abundant content of biologically active compounds, Althaea officinalis L. (marshmallow) has been extensively researched and applied in both the food and pharmaceutical industries. This study aimed to evaluate hydroethanolic and natural deep eutectic solvent (NADES) extracts from leaves, flowers, and roots in terms of their chemical composition and biological activities. Extracts were characterized using chromatographic and spectrophotometric methods. Phytochemical profiling by HPLC-MS revealed a diverse composition, with 35 secondary metabolites identified or tentatively assigned, mainly hydroxycinnamic acid derivatives and flavonoid glycosides. GC-MS analysis of the ethanol extracts identified ten free amino acids, seven organic acids, several mono- and disaccharides, and one oligosaccharide. Their concentrations varied across different parts of the plant depending on the specific metabolism of the respective organ. Ethanolic extracts showed the highest total phenolic content (up to 176 mg GAE/L), while flower extracts exhibited the strongest antioxidant activity (DPPH up to 89 µmol TE/L). The antimicrobial potential of the extracts was assessed by the agar well diffusion method. NADES1 extracts demonstrated significant antibacterial activity, with inhibition zones reaching up to ~34 mm, whereas NADES2 extracts were largely inactive. In contrast, antifungal activity was negligible or absent across all samples.