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Newcastle University (2007)

Evaluation of selected Libyan medicinal plant extracts for their antioxidant and anticholinesterase activities

Elmestiri, Fatma M. 

Titre : Evaluation of selected Libyan medicinal plant extracts for their antioxidant and anticholinesterase activities

Auteur : Elmestiri, Fatma M. 

Université de soutenance : Newcastle University

Grade : Doctor of Philosophy (PhD) 2007

Résumé
In different parts of the world, the use of medicinal plants has always been important in the therapeutic armory of mankind and remains an important source for the discovery of new bio-active compounds. Libya constitutes an apt example where medicinal plants are widely used. While some individual plant species such as Ginkgo biloba have been investigated in some detail, there is relatively little information available concerning the antioxidant potential and anticholinesterase activities of plant species in general and Libyan plants in particular. In this study twenty three Libyan medicinal plants were chosen for the study of antioxidant capacity and phenolic content. Aqueous plant extracts were screened for their antioxidant activity using the FRAP, TEAC and DPPH methods. These methods enable high-throughput screening of potential antioxidant capacity. Results show that of these twenty three plants, hot and cold extracts of Myrtus communis, Quercus robur and Syzygium aromaticum exhibited the strongest antioxidant activity in all tests and this is higher than that of the green tea control. It is suggested that the efficacy of these plants could be explained, at least in part, by their antioxidant activity. A selection of ten Libyan plants which have various ethnobotanical uses were evaluated for anticholinesterase activity. Most plants screened showed some inhibitory activity with either or both acetyl- and butyrylcholinesterase. Digestion is an initial step involving changes in pH and activity of proteolytic enzymes. Plant extracts were evaluated for possible changes in antioxidant properties and anticholinesterase activity using an artificial digestion technique. Most extracts showed an increase in antioxidant activity after the final pancreatin step although results varied with the antioxidant assay used. However, almost all anticholinesterase activity was lost at the HC1 stage of the in vitro digestion procedure. Testing in vitro bioavailability of plant extracts is a useful step in evaluating in vivo bioavailability.

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