Theses (MSc. Medical and Health Sciences)

Loss of neurons, excessive accumulation of beta-amyloid (Aβ) peptides in certain brain regions along with accumulation and excessive stimulation of glutamate receptors in the central nervous system (CNS) are common pathological hallmarks of neurodegenerative disease such as Alzheimer’s disease (AD). Although a number of drugs have been approved for the treatment of AD, most of these synthetic drugs have diverse side effects and yield relatively modest benefits. Marine algae have great potential in pharmaceutical and biomedical applications as they are valuable sources of bioactive properties. Hence, this study aimed to provide an overview of potentials of Malaysian seaweeds (Padina australis, Sargassum polycystum, Turbinaria ornata and Caulerpa racemosa) in inhibiting cholinesterase (ChE) enzymes, Aβ-induced and glutamate-induced toxicity. Cholinesterase inhibitory activity was conducted using Ellman’s colorimetric assay while protective effects against Aβ-induced and glutamate-induced toxicity were assessed by determining percentage of viable cells using MTT assay. C. racemosa and S. polycystum showed the most potent anti-acetylcholinesterase activities with the IC50 values ranging from 0.086-0.115 mg/mL. Moreover, C. racemosa and T. ornata were also found to be active against butyrylcholinesterase with IC50 values ranging from 0.118-0.162 mg/mL. Seaweed with dual anti-cholinergic activity is an important finding in this study, as C. racemosa methanol extract and caulerpin exhibited very potent inhibitory activities against both enzymes. Besides that, methanol extract of C. racemosa and caulerpin showed very good neuroprotective effect against beta-amyloid1-42 induced toxicity. In evaluating glutamate-induced toxicity, T. ornata dichloromethane extract had 143.02% viable cells at 0.00030 mg/mL. Moreover, the cell viability continues to increase in the presence of seaweed extracts for other seaweeds extracts except T. ornata extracts. It is extremely noteworthy that the extracts that gave good ChE inhibition activity also gave best protection against Aβ and glutamate induced toxicity. These findings suggest that Malaysian seaweeds have potential to be used as neuroprotective agents in treatment of AD.