[AVX Seminar] The ecosystem of Serra da Estrela: plant biodiversity and bioactive compounds from underexplored natural sources

Avx Seminar

Title: The ecosystem of Serra da Estrela: plant biodiversity and bioactive compounds from underexplored natural sources

Speaker: Ana Paula Duarte

Affiliation: Centro de Investigação de Ciências da Saúde da Universidade da Beira Interior

Abstract

The ecosystem of Serra da Estrela has a very rich vegetal biodiversity and some plant species have the potential to be used as raw material for extraction of bioactive products. The goal of our team is to screen the bioactivity of extracts of these plants, some of which are used in traditional medicine. So, phytochemical compounds as total phenolics, tannins, flavonoids and alkaloids, as well as, the identification of phenolic compounds using RP-HPLC, were carried out with the extracts of some plants (shrubs and/or trees) such as Echinospartum ibericum, Pterospartum tridentatum, Juniperus communis, Ruscus aculeatus, Rubus ulmifolius, Hakea sericea, Cytisus multiflorus, Crataegus monogyna, Ailanthus altissima (Miller) Swingle, Erica spp. and Ipomoea acuminata.

The antioxidant and antimicrobial activities were evaluated for these extracts and most of the studied shrubs showed significant antioxidant properties, which are probably due to the contents in phenolic compounds. According to the results obtained in this screening study, Hakea sericea extracts showed the best results and were selected for further studies. This shrub has been introduced in Portugal for ornamental purposes and no phytochemical or biological studies were known.

The antimicrobial activity and toxicity of extracts of this shrub against several Gram-positive, Gram-negative and yeasts, were evaluated. Regarding the antimicrobial activity, the extracts were more effective against Gram-positive bacteria. The fruits extract yielded the lowest MIC for several strains of microorganisms, namely, S. aureus, B. cereus, L. monocytogenes and clinical MRSA. This extract showed a significant activity against the food borne pathogens, B. cereus and L. monocytogenes, indicating a potential use of this plant as food preservative. Regarding leaves extract, hemolysis was not observed, and in the case of stems and fruits, hemolysis was verified only for higher concentrations, suggesting its low toxicity. Fruits extract presented no toxic effect to normal human dermal fibroblasts (NHDF) cells however for concentrations of 0.017 and 0.008 mg/mL this extract was able to decrease human breast adenocarcinoma cells (MCF-7) cells viability in about 60%, as MTT test results had confirmed.

The crude methanolic extract of H. sericea fruits was subjected to a bioassay-guided fractionation and the compound 9-(3,5-dihydroxy-4-methylphenyl)nona-3(Z)-enoic acid was isolated for the first time. The structure of this new compound was established by one- and two-dimensional NMR and IR spectroscopy, and high-resolution mass spectrometry.

Other plants of this group, usually used in traditional medicine, were also subjected to further antimicrobial studies, namely, Erica spp. and C. monogyna, showing antilisterial activity in the case of Erica spp. and a synergistic effect with amphotericin B against Candida species, in the case of C. monogyna.

Other study concerning natural sources from the region was directed to sweet cherries from Fundão, namely by using simulated digestion and Caco-2 cells for assessing the in vitro bioavailability of its phenolic compounds. In addition, the Saco cultivar extract highly-enriched in anthocyanins presented the capacity to target the hallmarks of cancer in LNCaP human prostate cells: diminishing cell viability, increasing apoptosis and suppressing glycolytic metabolism.