Bioactive compounds from endemic plants of Southwest Portugal: Inhibition of acetylcholinesterase and radical scavenging activities

Abstract

Context: Natural products are reported to have substantial neuroprotective activity due to their radical scavenging capacity, and also acetylcholinesterase (AChE) inhibitory capacity, both activities important in neurodegeneration.

Objective: The undesirable side effects of compounds in pharmacological use make it important to identify natural neuroprotective molecules. This work assesses the potential of five endemic Portuguese plants as sources of neuroprotective compounds.

Materials and methods: Antioxidant capacity for peroxyl radical was determined by Oxygen Radical Absorbance Capacity method and for hydroxyl by Electron Paramagnetic Resonance, as well as AChE inhibitory capacity of the plant hydroethanolic extracts. The molecules responsible for these valuable properties were also tentatively identified by HPLC.

Results and discussion: Armeria rouyana and Thymus capitellatus presented some of the highest phenolic contents (76.60 ± 7.19 and 12.82 ± 0.24 mg GAE g⁻¹ dw, respectively) and antioxidant capacities (592 ± 116 and 449 ± 57 μmol TE g⁻¹ dw, respectively). The flavonoids were identified as the phytomolecules related to the antioxidant capacity of these plant extracts; in the case of A. rouyana, l-ascorbic acid also made an important contribution (3.27 ± 0.26 mg g⁻¹ dw). Plant extracts clearly demonstrated effective AChE inhibitory activity (480 ± 98 and 490 ± 46 μg mL⁻¹, respectively), that could be associated to polyphenols.

Conclusions: The extracts of A. rouyana and T. capitellatus and their active components, especially polyphenols, demonstrate interesting neuroprotective potential. They, therefore, deserve further study as their phytomolecules are promising sources of either natural neuroprotective products and/or novel lead compounds.

Keywords:

• Portuguese endemic plants
• polyphenols
• antioxidant capacity
• acetylcholinesterase inhibitor
• neuroprotective phytomolecules

Acknowledgments

The authors wish to thank the Fundação para a Ciência e Tecnologia for financial support of C. Santos (SFRH/BPD/26562/2006), L. Tavares (SFRH/BD/37382/2007) and A. Serra (SFRH/BD/19238/2004).

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.