Turmeric (Curcuma longa) is extensively used as a spice and a coloring agent in Southeast Asia. Turmeric is used as a traditional remedy for cough, diabetic wounds, hepatic disorders, and rheumatism due to its antiseptic, antibacterial, and anti-inflammatory properties. Since the last few decades, extensive work has been done on turmeric and its constituents to explore its pharmacological actions. Curcumin is the main constituent of turmeric and is well demonstrated for its anti-inflammatory, hypoglycaemic, antioxidant, wound-healing, and antimicrobial activities. The functional neurons of the brain and synapses are lost in neurodegenerative disorders for which there is no permanent cure. Oxidative damage and inflammation play a role in age-related neurological disorders. The antioxidants have the ability to prevent different neurological disorders. Recent studies have shown that both turmeric and curcumin possess neuroprotective and cognitiveenhancing properties that help to prevent neurodegenerative diseases like Alzheimer's disease and Parkinson’s disease. Different experimental studies have indicated the antioxidant and anti-ageing properties of turmeric and curcumin. Various studies have shown that curcumin acts as a strong barrier against neurological disorders and, hence, it may be a potential drug candidate for the prevention of neurodegenerative diseases. The aim of this review was to present the current pieces of evidence in the literature regarding the neuroprotective effects of turmeric and curcumin.

Of many neurodegenerative diseases, Alzheimer’s disease (AD) is the most common cause of dementia globally, which is still incurable even after decades of extensive research to find a definite and permanent cure. Accumulation of free radicals and acetylcholine (ACh) deficiency in the brains of Alzheimer’s patients are considered as the factors leading to dementia and cognitive problems. This is by mechanisms involving disturbance in the balance between the amount of free radicals and the antioxidant defense system along with cholinergic deficit leading to impaired cholinergic neurotransmission. Currently available anti-AD drug therapy carries only the partial benefit of slowing down the progression of disease besides having various side effects and, hence, there is a developing interest to search for new drugs. Plants have always been of special interest in the field of new drug discovery research by virtue of their enormous biological diversity and tremendous potential of bioactive molecules. Many herbs are known to ameliorate the symptoms related to memory and cognitive disorders. Centella asiatica (L.) Urb. is one of the widely used plants claimed by the traditional system of medicine to have its positive effects on memory and brain functioning. The objective of this review is to present a comprehensive account on C. asiatica by summarizing the research until date related to its medicinal potential with a special focus on antioxidant and anti-acetylcholinesterase (antiAChE) properties reflecting their potential therapeutic application for the treatment of AD.

Clinacanthus nutans is a great medicinal herb with high polyphenols content and had been used in its infusion form to treat illness. In this paper, microwave-assisted extraction of C. nutans tea infusion was investigated by using central composite design combined with response surface methodology. The influence factors of microwave power (80 - 800 W); brewing time duration (0 – 240 s) and extraction time duration (60 s – 300 s) on total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity (DPPH) and acetylcholinesterase inhibition activity (AChE) were investigated. The optimum extraction conditions were determined as follows: microwave power X1, 560 W; brewing duration, X2, 60 s and extraction time, X3, 240 s. Under this optimal extraction conditions, the responses were as followed: Total phenolic content (251.58±10.98 mg GAE/L); Total flavonoid content (102.21±5.16 mg RE/L); DPPH (62.22±0.03%) and acetylcholinesterase inhibition activity (AChE) of 24.77±0.12%. Results demonstrated that MAE could be used to extract bioactive constituents having antioxidant and anti-acetylcholinesterase properties that may benefit in Alzheimer’s disease.