Antioxidant and anti-acetylcholinesterase activities of selected plants from Asteraceae family related to Alzheimer’s disease: A review

Abstract

Alzheimer’s disease (AD) is often associated with deficit levels of neurotransmitters acetylcholine (ACh) due to hydrolysis by acetylcholinesterase (AChE). Oxidative damage is also found to contribute to AD. Since neurons are vulnerable to high amounts of reactive oxygen species (ROS), damaged neurons lead to declined cognitive and learning abilities. In addition, the current medications for AD pose worrying side effects to AD patients.  Hence, more efforts have been made to discover the potential of plants in providing safer alternatives for AD treatment since they are rich with bioactive compounds like phenolics and flavonoids. The scope of this review is narrowed to Asteraceae family plants: Achillea filipendulina, Achillea millefolium, Artemisia herba-alba, Calendula officinalis, Enhydra fluctuans and Hertia cheirifolia. In the present study, the relationship between total phenolic content (TPC), total flavonoid content (TFC) and antioxidant property have been investigated in these plants subjected to different extraction techniques, plant parts, solvent polarity, type of extracts and plant harvesting period. Effects of these factors in anti-AChE activity were also discussed. Besides that, the possible synergistic effects between antioxidant and anti-AChE in the plants have been identified. The summarised results have proven that different extraction parameters bring about different bioactivity intensities. Next, results showed a strong, positive relationship between TPC, TFC and antioxidant activity except for C. officinalis where its root methanolic extract demonstrated an opposite trend. Furthermore, possible dual effects in plants were detected in four out of five plants reviewed except for A. herba-alba methanolic extract whereby the plant exhibited greater antioxidant properties while its essential oil demonstrated stronger anti-AChE properties. This study emphasized the paramount importance of considering all factors that influence the composition of bioactive compounds and their desired biological activities. Moreover, our findings on the knowledge of possible dual effects in selected plants could advance the development of therapeutic drugs in AD treatment.