ABSTRACT

Alzheimer’s disease (AD) is the most common cause of dementia, mainly in an elderly population. The incidence of AD not only increases in developed countries, but increasing cases is estimated in developing countries by 2025. The cause of AD is poorly understood thus it is necessary to discover a marker which is able to accurately detect AD at an early stage. In addition to beta amyloid (Aβ), tau protein is also one of the important biomarkers of AD. We aim to review the studies focused on tau protein as a greater therapeutic target due to its significantly elevated levels and hyperphosphorylation in AD and how tau protein can be targeted by several tropical medicinal plants. Increased tau levels and hyperphosphorylation has been observed to be independently contributed in AD pathogenesis and progression, therefore, new therapeutic strategies to reduce tau hyperphosphorylation are needed. The current study is based on pertinent papers that were retrieved using relevant keywords in PubMed and Science Direct. The literature searches mainly focusing on the tropical medicinal plants with activity in targeting tau protein were identified. This review presents various tropical medicinal plants that have been scientifically proven on their effects as tau-targeting drug on AD, such as Curcuma longa, Cinnamomum zeylanicum, Camellia sinensis, Vitis vinifera, Salvia militorrhiza, Nicotiana tabacum, Rosmarinus officinalis, Capsicum annuum, Lavandula angustifolia, Cocos nucifera and Panax notoginseng. The medicinal plants targeting tau protein mainly exhibited the effect through increasing tau clearance, reducing tau phosphorylation and/or inhibiting tau aggregation. Preclinical studies have shown those plants as new potential therapeutic agents for patient with AD, however, further studies are highly required to demonstrate the safety and efficacy of these medicinal plants uses in patient with AD.

Keywords: Alzheimer’s disease; Tau protein; tropical medicinal plants; mechanism of action