The physicochemical, antioxidant and antimicrobial properties of selected Portuguese commercial honeys have been characterized aiming at establishing correlations between honey bioactivity and the physicochemical descriptors. All honey samples met the European regulations on honey quality criteria, including moisture and sugar content, free acidity, diastase activity, electrical conductivity, ashes, hydroxymethylfurfural and proline content. Antioxidant activity was evaluated based on phenolic and flavonoid content, 2,2-diphenyl-1picrylhydrazyl (DPPH) radical scavenging activity, ferric reducing antioxidant power (FRAP) and oxygen radical antioxidant capacity (ORAC) assays. The honeys showed antibacterial and antifungal activity with minimum inhibitory concentrations (MIC) between 6.25-25% (w/v) and minimum fungicidal concentrations (MFC) in the range 12.5-50% (w/v), respectively. The bioactivity and physicochemical parameters of honey samples were correlated and depended on the honey floral source. The darkest honey, i.e. heather honey, showed the highest antioxidant and antimicrobial activities, which can be attributed to its higher phenolic, flavonoid and protein content.

Ethnopharmacological Relevance:Plectranthus genus (Lamiaceae family) contain several species with acknowledged ethnopharmacological uses, such as, for gastrointestinal and respiratory-related problems, due to their anti-inflammatory, antibacterial and antifungal properties. The bioactivity of isolated medicinal compounds from this genus justifies the increased interest in recent times for species of Plectranthus, placing them in the spotlight for natural product drug development.Aim of the study: To the best of our knowledge, this is the first review on the biological activities of Plectranthus ecklonii Benth. As such, the aim of this review was three-fold: 1) to summarize the chemical compounds isolated from P. ecklonii; 2) to collate the biological activities and mechanisms of action of these compounds from in vitro studies; and 3) to evaluate the documented uses and potential applications of this species, in order to postulate on the direction of pharmaceutical uses of this species.Materials and methods: An extensive database retrieval was performed using the electronic databases Web of Science, PubMed, Google Scholar and ScienceDirect. The search criteria consisted of the keywords “Plectranthus ecklonii”, “Plectranthus ecklonii + review”, “Plectranthus ecklonii + diterpenes” or “Plectranthus ecklonii + abietanes”, “ecklonii + parviflorone D”, searched individually and as combinations. Eligibility criteria were set out and titles in English, Portuguese and Spanish were reviewed, with all references included dating from 1970 to 2021. A total of 169 papers were selected and included. Chemical structures were drawn using ChemDraw 20.0, CID numbers were searched in PubChem and the PRISMA diagram was created using PowerPoint 2012.Results: To date, a total of 28 compounds have been isolated from P. ecklonii, including diterpenes, triterpenes, flavonoids, and hydroxycinnamic acids. Most focused on the antimicrobial action of its constituents, although compounds have demonstrated other bioactivities, namely antioxidant, anti-inflammatory and antitumor. The most recent studies emphasize the diterpenoids, particularly parviflorone D, with the help of nanotechnology.Conclusions: The widespread ethnobotanical and traditional uses of P. ecklonii can be scientifically justified by a range of biological activities, demonstrated by isolated secondary metabolites. These bioactivities showcase the potential of this species in the development of economically important active pharmaceutical ingredients, particularly in anticancer therapy.

Glioblastoma (GB) is the most malignant and frequent primary tumor of the central nervous system. The lack of diagnostic tools and the poor prognosis associated with this tumor type leads to restricted and limited options of treatment, namely surgical resection and radio-chemotherapy. However, despite these treatments, in almost all cases, patients experience relapse, leading to survival rates shorter than 5 years (∼15–18 months after diagnosis). Novel therapeutic approaches are urgently required (either by discovering new medicines or by repurposing drugs) to surpass the limitations of conventional treatments and improve patients’ survival rate and quality of life. In the present work, we investigated the antitumor potential of parvifloron D (ParvD), a drug lead of natural origin, in a GB cell line panel. This natural drug lead induced G2/M cell cycle arrest and apoptosis via activation of the intrinsic mitochondria-dependent pathway. Moreover, the necessary doses of ParvD to induce pronounced inhibitory effects were substantially lower than that of temozolomide (TMZ, first-line treatment) required to promote comparable effects. Therefore, ParvD may have the potential to overcome the resistance related to TMZ and contribute to the pursuit of hopeful treatments based on ParvD as a drug lead for future chemotherapeutics.

Editorial on the Research TopicConsidering plant metabolites and their synthetic derivatives as candidates for the development of drugs against multidrug resistant (MDR) tumors Despite the great benefits of chemotherapy, the ability of tumor cells to acquire crossresistance to multiple antineoplastic drugs (MDR) results in a drastic reduction in the efficacy of these agents. Of greatest concern is the consequent failure in clinical practice, which remains one of the major barriers to successful cancer treatment. To improve patient outcome, novel efficacious anti-cancer agents or approaches to reverse MDR are necessary.Plants have been an endless and vital source of pharmacologically active compounds, many of which are widely used in cancer therapies, not only to control tumor cells, but also to increase their sensitivity to chemotherapeutic agents. The structural diversity and array of biological properties of plant-derived metabolites, in particular against tumors, make these strong candidates to combat MDR cells or establish their scaffolds as a valuable base for the synthesis of derivatives.This enormous potential of plants to tackle MDR tumors encouraged us to publish this Research Topic to display and discuss the cutting-edge research in the field. As editors, it was a pleasure to review a wide range of fascinating articles with different perspectives, and we summarize here the main findings of accepted articles.