Estudo das propriedades antioxidante e antimicrobiana de extractos de Mentha Cervina

Abstract

Mentha cervina (L.) Opiz (Lamiaceae) is a type of mint that grows wild in the river banks of the north-western regions of the Iberian Peninsula. It is an aromatic plant used for culinary purposes, especially to aromatize fish dishes, and for its medicinal properties, namely in infusions with digestive properties. The main objective of this work was to analyze the antioxidant and antimicrobial activity of Mentha cervina extracts - infusions, tinctures and essential oils - in order to assess its potential for the development of functional ingredients that may be applied in the food or cosmetic industries. The antioxidant activity of the tinctures (ethanol/water mixtures) and of the infusions was assessed by the ABTS.+ method, total phenol content by the Folin-Ciocalteu method and the LC-MS/MS analysis was performed directly on the crude extracts for the identification of phenolic compounds. For the essential oil the TEAC method was applied to evaluate the antioxidant properties. The antimicrobial activity of essential oil was assessed by disc diffusion and MIC assays, being this property, in the tinctures and infusions, analysed by the agar well diffusion method. The biologic potential for antioxidant activity of all extracts was analysed by the protection of DNA from oxidation . The hydroethanolic extracts of stem at 65 % ethanol and of leaves at 40 % ethanol showed the highest antioxidant activity. However, when the analysis was based on dry matter only the stem at 65% ethanol exhibited the highest antioxidant capacity. The extract obtained from leaves at 65 % ethanol presented a highest total phenol content in solution. Nevertheless, when the study was based on dry matter, the stem at 65 % ethanol revealed the highest content of phenolic compounds. All extracts, except for the essential oils, protected DNA from degradation by oxidation, but hydroethanolic extracts showed the highest protection. The main phenolic compounds identified by LC-MS/MS in the extracts where caffeic acid and cholorogenic acid. Both tinctures and infusions didn‟t inhibit the pathogenic or food contaminants microorganisms, but the essential oil inhibited E. coli, Salmonella spp., S.aureus, S. aureus ATCC, Listeria innocua, B. cereus, Candida albicans and Yarrowia lipolytica. Essential oil of M. cervina showed better efficiency against Gram negative bacteria and yeast, demonstrated by the complete inhibition observed in their growth curve.

Date of Award	2011
Original language	Portuguese
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Maria Manuela Pintado (Supervisor), Susana Carvalho (Co-Supervisor), Matteo Politi (Co-Supervisor) & Paula M. L. Castro (Co-Supervisor)