Reneta Gevrenova | Medical University - Sofia (original) (raw)

Papers by Reneta Gevrenova

Pharmacognosy Magazine, 2015

Arnica montana flowers have a long history as herbal medicines for external use on injuries and r... more Arnica montana flowers have a long history as herbal medicines for external use on injuries and rheumatic complaints. To investigate Arnicae flos of cultivated accessions from Bulgaria, Poland, Germany, Finland, and Pharmacy store for phenolic derivatives and sesquiterpene lactones (STLs). Samples of Arnica from nine origins were prepared by ultrasound-assisted extraction with 80% methanol for phenolic compounds analysis. Subsequent reverse-phase high-performance liquid chromatography (HPLC) separation of the analytes was performed using gradient elution and ultraviolet detection at 280 and 310 nm (phenolic acids), and 360 nm (flavonoids). Total STLs were determined in chloroform extracts by solid-phase extraction-HPLC at 225 nm. The HPLC generated chromatographic data were analyzed using principal component analysis (PCA) and hierarchical clustering (HC). The highest total amount of phenolic acids was found in the sample from Botanical Garden at Joensuu University, Finland (2.36 mg/g dw). Astragalin, isoquercitrin, and isorhamnetin 3-glucoside were the main flavonol glycosides being present up to 3.37 mg/g (astragalin). Three well-defined clusters were distinguished by PCA and HC. Cluster C1 comprised of the German and Finnish accessions characterized by the highest content of flavonols. Cluster C2 included the Bulgarian and Polish samples presenting a low content of flavonoids. Cluster C3 consisted only of one sample from a pharmacy store. A validated HPLC method for simultaneous determination of phenolic acids, flavonoid glycosides, and aglycones in A. montana flowers was developed. The PCA loading plot showed that quercetin, kaempferol, and isorhamnetin can be used to distinguish different Arnica accessions. A principal component analysis (PCA) on 13 phenolic compounds and total amount of sesquiterpene lactones in Arnicae flos collection tended to cluster the studied 9 accessions into three main groups. The profiles obtained demonstrated that the samples from Germany and Finland are characterized by greater amounts of phenolic derivatives than the Bulgarian and Polish ones. The PCA loading plot showed that quercetin, kaemferol and isorhamnetin can be used to distinguish different arnica accessions.

Biochemical Systematics and Ecology, Jun 9, 2013

Leaves of 22 accessions of the Bulgarian raspberry (Rubus L.) germplasm collection -five Bulgaria... more Leaves of 22 accessions of the Bulgarian raspberry (Rubus L.) germplasm collection -five Bulgarian and seven foreign cultivars, eight elite clones and two wild species, Rubus occidentalis L. and Rubus odoratus L., were analysed for phenolic constituents. The quantitative determination of caffeic (1), p-coumaric (2) and ferulic (3) acids, hyperoside (4), tiliroside (5), and isoquercitrin (6) was performed by RP-HPLC using linear gradient elution and UV detection at 254 and 310 nm. The detection limits ranged from 0.23 mg/ml (4) to 0.55 mg/ml (2). Caffeic acid was the dominant phenolic acid in the majority of the samples being present in amounts between 0.05 AE 0.01 mg/g dry weight in R. occidentalis and 1.43 AE 0.06 mg/g in the cultivars. The highest content of flavonols was found in the Bulgarian raspberry elite clones: 1.70 AE 0.002 mg/g (6), 0.60 AE 0.004 mg/g (5) and 0.97 AE 0.01 mg/g (4). Data were analyzed by hierarchical clustering (HC) and principal component analysis (PCA). The HC and PCA scoring plot showed that the samples could be classified into three clusters. Cluster C1 comprised cultivars characterized by high content of phenolic acids (1-3). Seven cultivars and the wild species R. occidentalis formed the cluster C2 presenting low content of phenolic compounds. Cluster C3 grouped the Bulgarian raspberry elite clones and R. odoratus sharing the highest content of flavonols (5 and 6). The Bulgarian elite clone E23617 displayed the highest content of the studied phenolic derivatives. The PCA loading plot showed that 1 can be used to distinguish between different raspberry varieties. (I. Badjakov), mtihomirova@yahoo.co.uk (M. Nikolova), idoytchinova@pharmfac.net (I. Doichinova).

ABSTRACT Export Date: 18 October 2014

Indexed in: MeDLINe, cAplus sM /chemical Abstracts, toXceNteR, eMBAse/excerpta Medica, PAscAL, BI... more Indexed in: MeDLINe, cAplus sM /chemical Abstracts, toXceNteR, eMBAse/excerpta Medica, PAscAL, BIotecHNoBAse, extraMeD tM , scoPUs Editorial/publishing policy: Manuscripts submitted to PHARMACIA are only accepted on the understanding, that they are subject to editorial review and review of at least two independent referees, that they have not been and will not be bublished whole or in part in any other journal and that recommendations to comply with with ethycal standards when performing clinical and other biological experiments have been adhered to. Publishing frequency is four times a year (volume). Only abstracts published in the Journal may be reproduced without prior permission; reproduction of other materials requires publisher's consent.

A solid-phase extraction (SPE) method followed by a reverse-phase high-performance liquid chromat... more A solid-phase extraction (SPE) method followed by a reverse-phase high-performance liquid chromatography (RP–HPLC) is reported for the assay of flavonoids in aerial parts of Bupleurum flavum Forsk. (Apiaceae). Fractiona-tion of flavonoid glycosides by means of SPE allowed a good recovery of an-alytes (up to 99%). An HPLC separation of the flavonol glycosides with run time of 9 min was performed on a Hypersil ODS C18 column using isocratic elution and UV detection. The optimized SPE–HPLC method was validated for precision, linearity, accuracy, limit of detection and limit of quantification. The precision of the entire analytical procedure was < 6%. Narcissin was the dominant glycoside being present in 64.10 ± 3.50 mg g −1 dry hydroalcoholic extract. The amount of total polyphenols and flavonoids was evaluated spec-trophotometrically and was found to be 350.59 ± 9.28 mg g −1 and 72.60 ± 0.04 mg g −1 respectively. Antioxidant activity of B. flavum hydroalcoholic extract was establis...

A reliable solid-phase extraction – high-performance liquid chromatography (SPE-HPLC) method for ... more A reliable solid-phase extraction – high-performance liquid chromatography (SPE-HPLC) method for the determination of flavonoids in European Bupleurum species B. baldense Turra and B. affine Sad-ler was developed. Extraction of aerial parts by ultrasound with 80% aqueous methanol and fractionation of flavonoids by means of SPE allowed a good recovery of analytes between 99 and 104%. The subsequent HPLC separation of the flavonoids was performed on a Luna C18 column using gradient elution and UV detection. The optimized SPE-HPLC method was validated for precision, linearity, accuracy, recovery, limit of detection and limit of quantification. The precision of the entire analytical procedure was < 2%. The total amount of assayed flavonoids was 11.53 mg/g dry weight (B. affine) and 39.16 ± 0.92 mg/g (B. baldense). Rutin was the dominant flavonol glycoside in B. baldense being present at 28.63 ± 1.57 mg/g, whilst B.affine demonstrated lower levels of flavonoids.

The quantitative determination of protocatechuic, chlorogenic and caffeic acids in Arnica montana... more The quantitative determination of protocatechuic, chlorogenic and caffeic acids in Arnica montana by reverse phase high-performance liquid chromatog-raphy (RP–HPLC) was carried out. Samples of Arnicae flos from eight different origins were selected for the assay as follows: one Bulgarian and one Polish culti-vated collection, two cultivars, three collections grown in the Botanical Garden in Finland and one is purchased from a Pharmacy Drugstore. The effect of extracting solvent was investigated and optimal extraction of assayed phenolic acids was achieved by 80% methanol. The subsequent HPLC separation of the analytes was performed on Hypersil ODS C 18 column using linear gradient elution with a mobile phase composed of 20 mM phosphate buffer (pH 3.22) and methanol, and with UV detection at 280 and 310 nm. The detection limits were 0.19 µg/ml, 0.51 µg/ml and 0.33 µg/ml for protocatechuic, chlorogenic and caffeic acids, respectively and the quantification limits were 0.57 µg/ml, 1.53...

Biotechnology & Biotechnological Equipment, 2008

The international tendency for growing and production of small fruits shows a permanent increasin... more The international tendency for growing and production of small fruits shows a permanent increasing. Bulgaria is a traditional important producer of small berries in Europe. A large variety of small fruit products are wide spread and typical for Bulgarian nutriment. Aside with the growing demand in production of small fruit, there is an obvious tendency in food quality, breeding and technology requirements improvement. Breeding purposes comprise improvement of many traits, but selection of disease resistant cultivars, with higher yield and improved consumers properties such as fruit color, shape, smell and transportation ability are among the most important tasks.

Journal of Functional Foods, 2015

Industrial Crops and Products, 2014

Asphodeline lutea (L.) Rchb. is a wild edible plant, traditionally consumed in the Mediterranean ... more Asphodeline lutea (L.) Rchb. is a wild edible plant, traditionally consumed in the Mediterranean diet, but there are limited literature data about its medicinal properties. Methanol extracts of A. lutea roots from Bulgarian (ALB) and Turkish (ALT) origin were evaluated for their antioxidant activity using various in vitro models: phosphomolybdenum assay, free radical scavenging activity, metal chelating activity and ferric and cupric reducing power. Both methanolic extracts were analyzed for phenolic derivatives by HPLC-DAD. Caffeic acid was the dominant phenolic acid being present up to 2.19 ± 0.020 mg/g extract in ALB. The highest content of (+) catechin (1.54 ± 0.060 mg/g) and (−) epicatechin (3.18 ± 0.160 mg/g) was found in ALB as well as total polyphenolics (22.45 ± 0.95 mg/g GAEs/g extract). The ALT revealed the highest total flavonoid content (34.99 ± 0.39 mg REs/g extract). Free radical scavenging activity of ALB against DPPH (25.39 ± 0.36 mg TEs/g extract) and ABTS (33.99 ± 1.06 mg TEs/g) was evaluated. In addition, ALB had stronger metal chelating activity (7.31 ± 0.31 mg EDTAEs/g extract) and higher ferric (34.67 ± 0.51 mg TEs/g extract) and cupric (23.82 ± 0.36 mg TEs/g) reduction ability as compared with the ALT. Total antioxidant capacity of ALB in phosphomolybdenum test was assayed (236.80 ± 0.86 mg AEs/g extract). A. lutea roots have a significant potential in safeguarding against various induced oxidative stress.

Letters in Drug Design & Discovery, 2014

Pharmaceutical Biology, 2014

Context: Saponins have been reported to possess antitumor properties, to inhibit angiogenesis and... more Context: Saponins have been reported to possess antitumor properties, to inhibit angiogenesis and to induce tumor apoptosis. Objective: To test the possible cytotoxic effect of crude extracts from four Caryophyllaceae species including Gypsophila paniculata L., Gypsophila trichotoma Wend., Saponaria officinalis L., and Dianthus sylvestris Wulffen on cultured monocyte/macrophage cell lines. Materials and methods: After acid hydrolysis of the methanol-aqueous extracts, two representative prosaponins of the Caryophyllaceae, gypsogenin 3-O-glucuronide and quillaic acid 3-O-glucuronide were purified using solid-phase extraction (SPE), then identified by ultra-performance liquid chromatography-electrospray/mass spectrometry (UPLC-ESI/MS). Cytotoxic activity of the crude extracts at concentrations ranging from 0.1 to 200 mg/ml was evaluated on rat alveolar macrophage NR8383 and human monocytic THP-1 cell lines. Apoptosis was determined by measuring caspase-3 activity. Results: Quantitative analysis by reversed-phase high-performance liquid chromatography (RP-HPLC) revealed a high content of gypsogenin 3-O-glucuronide in Gypsophila species roots (0.52-1.13% dry weight). At a concentration !10 mg/ml of crude extracts, a significant reduction of NR8383 and THP-1 cell lines viability was evidenced using the Trypan blue exclusion test. D. sylvestris extract exhibited the highest toxicity against THP-1 cells. Caspase-3 activation was evidenced after 4 and 24 h incubation of macrophages with 100 mg/ml of S. officinalis and G. trichotoma extracts, indicating apoptosis induction. Discussion and conclusion: Crude extracts from the assayed species revealed cytotoxic effects toward macrophage cell lines. In Gypsophila species, gypsogenin 3-O-glucuronide derivatives could be responsible for the observed cytotoxicity. Therefore, crude extract of Caryophyllaceae is worth investigating for the potential development of agents against cancer cells.

Planta Medica, 2012

Eleven triterpenoid saponins were isolated from the roots of Gypsophila trichotoma Wender. (G. tr... more Eleven triterpenoid saponins were isolated from the roots of Gypsophila trichotoma Wender. (G. trichotoma Wender. var. trichotoma) (Caryophyllaceae), together with one known compound. The structures were established on the basis of extensive NMR analysis ( 1 H, 13 C NMR, COSY, TOCSY, ROESY, HSQC, and HMBC), completed by analysis of HR-ESI-MS and ESI-MS n . The saponins have the commonly found gypsogenin as the aglycone substituted at C-3 with trisaccharide and at C-28 with oligosaccharide through a fucose residue, as saponins isolated from Gypsophila perfoliata L. originated from China. The oligosaccharide attached to C-28 is substituted with acetyl and (or) sulfate groups.

Phytochemical Analysis, 2007

The determination of 18 aromatic and arylaliphatic carboxylic acids in honey from different flora... more The determination of 18 aromatic and arylaliphatic carboxylic acids in honey from different floral origin using solidphase extraction (SPE) and reversed-phase high performance liquid chromatography (RP-HPLC) is reported. The behaviour of the solutes on SPE cartridges was predicted from preliminary calculations involving the pK a constants of the carboxylic groups, the noctanol:water partition coefficients and the distribution coefficients at different pH values of the conditioning and washing solvents. The proposed SPE isolation and pre-concentration of the acids was achieved on reversed-phase Bond Elut C 18 cartridges using an acetonitrile:tetrahydrofuran (1:1, v/v) elution system. RP-HPLC separations were performed on a Spherisorb ODS-2 column using linear gradient elution with a mobile phase composed of 20 mm phosphate buffer (pH 2.92) and methanol, and with UV detection. The reported SPE and RP-HPLC methods were applied to the analysis of 49 authentic honey samples from various floral sources and the results indicate that they may serve with respect to the quantitative control of a number of phenolic acids in plant-derived foods and medicinal plants.

Magnetic Resonance in Chemistry, 2006

The assignments of 1 H and 13 C NMR spectra of two new aminoacyl triterpene saponins from roots o... more The assignments of 1 H and 13 C NMR spectra of two new aminoacyl triterpene saponins from roots of Gypsophila trichotoma Wend. are reported. In addition to 1D NMR methods, 2D NMR techniques (COSY, TOCSY, ROESY, HSQC, HMBC, and HSQC-TOCSY) were used for the assignments. The structures were completed by analysis of HR

The determination of the colouring compounds apigenin (1), lawsone (2), juglone (3) and indigotin... more The determination of the colouring compounds apigenin (1), lawsone (2), juglone (3) and indigotin (4) in plant extracts using HPLC–UV/Vis methods is reported. The methods were applied to the analysis of 1–4 in ethanolic and propylene glycolic extracts originating, respectively, from chamomile (Chamomilla recutita [L] Rauschert, Asteraceae), henna (Lawsonia inermis L., Lythraceae), walnut (Juglans regia L., Juglandaceae) and natural indigo (In-digofera sp., Fabaceae). In the case of the indigo extracts, an optimized acid hydrolysis was applied. HPLC separations were performed on a Hypersil ODS RP18 column using linear gradient elution programs. The detection limits for 1–4 were 0.11, 0.6, 0.10, 0.089 μg mL-1 , respectively. The procedure did not involve any sample " clean-up " methods. The amounts of the colouring compounds ranged from 0.006 (3) to 0.13 mg mL-1 (4) in the ethanolic extracts and from 0.22 (2) to 1.44 mg mL-1 (4) in propylene glycolic extracts. The proposed HPLC methods are advantageous in terms of sample preparation and the selective separation of the compounds. The plant dye extracts are commonly used in hair colouring formulations. The results indicate that the methods developed may serve for the quantitative control of dying plants and cosmetic products.

International Journal of Botany, 2006

Flavonoid profiles of aerial parts of two subspecies of V. chamaedrys L. growing at different alt... more Flavonoid profiles of aerial parts of two subspecies of V. chamaedrys L. growing at different altitudes were investigated. Five external flavones apigenin, luteolin, luteolin 3`-methyl ether (chrysoeriol), luteolin 7,4`-dimethyl ether and scutellarein 6,4`-dimethyl ether ( ...

Enzyme and Microbial Technology, 2010

A simple and rapid method of excised root cultures from six Gypsophila species was performed allo... more A simple and rapid method of excised root cultures from six Gypsophila species was performed allowing continuous growth without phytohormones. Established on MH3 medium from solid-grown seedlings these roots were subcultured for 1 year on a solid medium before being transferred in a liquid medium to obtain substantial biomass for saponin content analysis. Morphologically, the different root lines presented different growth behaviors and different physical aspects: some have linear growth by the tip of the main axial root from the original seedling; others have additional lateral root initiations producing a hairy root-system more or less dense. A marked increase of biomass was observed in the light by comparison with dark conditions. Significant growth for Gypsophila glomerata was achieved within 3 weeks on liquid medium; biomass grew up to 50-fold in batch cultures reaching 10 g DW. The fingerprints of the saponin HPLC profiles of the six Gypsophila species were drastically different with at least up to 30 different saponins detected for some of them. The roots of Gypsophila elegans accumulated saponins up to 65 mg/g DW. These amounts were higher than in Gypsophila paniculata roots classically found as the best producing ones. On the contrary the root lines of G. glomerata showed a smaller quantitative amount of saponins (between 1.3 and 7.10 mg/g DW) than those of G. elegans but nearly the same HPLC profiles as for root extracts of G. paniculata plants grown directly in the fields.