Violeta Lopes

Dr. Violeta Lopes

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Research Focus & Metrics

Academic Career Length

11Years (2016-Present)

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

Representative Publications

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1 October 2016 in Industrial Crops and Products
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Journal Article
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ABAna Maria Barata
Ana Maria Barata
FRFilomena Rocha
Filomena Rocha
VLVioleta Lopes
Violeta Lopes
Ana Maria CarvalhoAna Maria Carvalho
Ana Maria Carvalho

28 April 2018 in Molecules
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Catarina Lourenço-LopesCatarina Lourenço-Lopes
Catarina Lourenço-Lopes
Eliana PereiraEliana Pereira
Eliana Pereira
MSMarina Soković
Marina Soković
Ana Maria CarvalhoAna Maria Carvalho
Ana Maria Carvalho
ABAna Maria Barata
Ana Maria Barata
Isabel FerreiraIsabel Ferreira
Isabel Ferreira
The aim of this study was to characterize the phenolic composition and evaluate the bioactivity of several samples of Lavandula pedunculata (Mill.) Cav, and to compare aqueous and hydroethanolic extracts. Plant materials were obtained by growing some accessions (seed samples) of various wild populations from different regions of Portugal conserved at the Portuguese Genebank in Braga. Phenolic compounds were analised by HPLC-DAD-ESI/MSn, antioxidant potential through in vitro assays (DPPH radical scavenging activity, reducing power and inhibition of lipid peroxidation), cytotoxicity on tumor cells (MCF-7, NCI-H460, HeLa and HepG2) and non-tumor (PLP2) cells, anti-inflammatory activity in rat RAW 264.7 macrophages, by the ability to inhibit NO production and antimicrobial potential by the microdilution method with INT dye (iodonitrotetrazolium chloride). Thirteen compounds were identified, being salvianolic acid B, rosmarinic acid and luteolin-7-O-glucuronide, the main compounds present, with values ranging between 44.3–582, 50.9–550, and 24.36–101.5 mg/g extract, respectively. L. pedunculata aqueous extract revealed a higher antioxidant potential (EC50 values between 14 to 530 μg/mL), which could be related to its higher concentration in phenolic compounds; however, the hydroethanolic extract showed a higher anti-inflammatory (lower EC50 values than 124 μg/mL) potential and antiproliferative capacity (lower GI50 values than 34 μg/mL). Thus, this study highlights the bioactive effects of this species and opens up possibilities of uses in food and pharmaceutical formulations. However, there are potential differences in such properties according to geographical origin of plant material, as in general, the samples from Alentejo presented higher results in all the bioactivities, compared with Trás-os-Montes samples.

3 October 2024 in Applied Sciences
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Ana Rita Soares MateusAna Rita Soares Mateus
Ana Rita Soares Mateus
Maria do Carmo SerranoMaria do Carmo Serrano
Maria do Carmo Serrano
Carina AlmeidaCarina Almeida
Carina Almeida
ASAndreia Martins Soares
Andreia Martins Soares
VLVioleta Lopes
Violeta Lopes
Ana Sanches SilvaAna Sanches Silva
Ana Sanches Silva
Oregano (Origanum vulgare L.) and thyme (Thymus mastichina L.) are popular aromatic plants used in the culinary sphere and are known for their antioxidant capacity. This study investigates the variability in the antioxidant capacity and phenolic profiles, focusing on flavonoids and phenolic acids, of oregano and thyme accessions from the Portuguese Bank of Plant Germplasm. The antioxidant capacity was assessed by measurements using the ferric-ion-reducing antioxidant power and DPPH radical scavenging activity assays, Total Phenolic Content, and individual phenolic compounds. Oregano extracts presented the highest total phenolic content (~2152 mg GAE/g DW), while thyme extracts showed the highest ferric-reducing antioxidant powers. However, both aromatic plants (~0.58 mmol TE/g DW) presented similar DPPH radical scavenging capacities. Rosmarinic acid was the major phenolic compound in methanolic extracts from oregano and thyme, but higher amounts were found in thyme (23.11 to 40.45 mg/g DW). The accessions of oregano and thyme showed statistical differences in the phenolic content and antioxidant capacity. This study provides valuable insights into the phenolic profile of Portuguese oregano and thyme, which could constitute potential sources of natural antioxidants and bioactive compounds, to be used by the food industry as natural food additives.

11 April 2024 in Foods
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Maria do Carmo SerranoMaria do Carmo Serrano
Maria do Carmo Serrano
MOMaria Conceição Monteiro André Oliveira
Maria Conceição Monteiro André Oliveira
VLVioleta Lopes
Violeta Lopes
ASAndreia Martins Soares
Andreia Martins Soares
Adriana Katherine Molina VargasAdriana Katherine Molina Vargas
Adriana Katherine Molina Vargas
ABAna M. Barata
Ana M. Barata
This study aimed to analyse the chemical profile and biological activities of 29 accessions of Brassica rapa (turnips) and 9 of Brassica napus (turnips and seeds) collections, maintained ex situ in Portugal. HPLC-HRMS allowed the determination of glucosinolates (GLS) and polyphenolic compounds. The antioxidant and antimicrobial activities were determined by using relevant assays. The chemical profiles showed that glucosamine, gluconasturtiin, and neoglucobrassin were the most abundant GLS in the extracts from the turnip accessions. Minor forms of GLS include gluconapoleiferin, glucobrassicanapin, glucoerucin, glucobrassin, and 4-hydroxyglucobrassin. Both species exhibited strong antioxidant activity, attributed to glucosinolates and phenolic compounds. The methanol extracts of Brassica rapa accessions were assessed against a panel of five Gram-negative bacteria (Enterobacter cloacae, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica subsp. enterica serovar, and Yersinia enterocolitica) and three Gram-positive bacteria (Bacillus cereus, Listeria monocytogenes, and Staphylococcus aureus). The extracts exhibited activity against S. enterica and S. aureus, and two showed inhibitory activity against E. coli and Y. enterocolitica. This study provides valuable insights into the chemical composition and biological properties of Brassica rapa and Brassica napus collections in Portugal. The selected accessions can constitute potential sources of natural antioxidants and bioactive compounds, which can be used in breeding programs and improving human health and to promote healthy food systems.

19 March 2024 in Foods
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Orlanda Viamonte PóvoaOrlanda Viamonte Póvoa
Orlanda Viamonte Póvoa
NFNoémia Farinha
Noémia Farinha
VLVioleta Lopes
Violeta Lopes
AMAlexandra Machado
Alexandra Machado
AFAna Cristina Figueiredo
Ana Cristina Figueiredo
Coriander is a medicinal and aromatic plant (MAP) traditionally cultivated and used in Alentejo, Portugal. However, few publications are available about its ethnobotanical applications. Four independent ethnobotanical surveys were carried out: throughout the region (2002–2003), in three villages (2013), and in city markets (2007 and 2022). Coriander was the most common fresh cultivated MAP (75% of the total area) and also the most representative MAP fresh herb in city markets. The leaves, mostly, were used fresh or frozen or transformed in piso. Some of the recipes have agro-industrial potential, such as piso and aromatized olive oil. Coriander essential oils (EOs) were isolated by hydrodistillation from aerial parts with inflorescence emergence (APIs) and from fruits, and fatty acids (FA) by solvent extraction from the fruits. Gas chromatography and gas chromatography-mass spectrometry analysis showed EOs dominated by n-decanal (21–24%), 2-trans-decenal (12–18%) and n-nonane (10–17%) in APIs, and linalool dominance (73–78%) in the fruits. Petroselinic acid (32–55%) was the dominant fatty acid. A literature survey on conventional and nonconventional extraction techniques showed a constancy in the dominant compounds isolated, highlighted piso as a home-made green-extraction procedure, but also reflected the relevance of coriander as a MAP with diverse industrial potential uses.

8 July 2023 in Plants
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Orlanda Viamonte PóvoaOrlanda Viamonte Póvoa
Orlanda Viamonte Póvoa
VLVioleta Lopes
Violeta Lopes
ABAna Maria Barata
Ana Maria Barata
NFNoémia Farinha
Noémia Farinha
The main goal of this work was to study the genetic erosion risk of plants with aromatic, medicinal and gastronomic applications in Portugal, particularly in the Alentejo region. The target species were coriander (Coriandrum sativum L.), hart’s pennyroyal (Mentha cervina L.) and pennyroyal (Mentha pulegium L.). The methodology involved direct observations and surveys (2002/2003 and 2011). The GE formula applied in Hammer’s studies was used to estimate genetic erosion. The main factors causing genetic erosion were the primary drivers of biodiversity loss: habitat loss, invasive species, and overexploitation influenced by human intervention such as the clearing of watercourses, vegetation control, grazing and desertification. The results indicate a reduction in individuals per species in Alentejo, with a net erosion loss of 11% for M. pulegium, 32% for M. cervina and 33% for C. sativum. The overall loss of accessions (genetic erosion risk) was higher in cultivated accessions (33%) than in wild accessions (11%), with an annual genetic erosion rate of 3.7% and 1.2%, respectively. The annual risk of genetic erosion for M. pulegium accessions collected in a natural habitat was 0.6%, which is much lower than the 3.7% for M. cervina. These results consolidate the importance of collecting and conserving genetic resources.