Evaluation of the Bioactive Composition and in vitro Neuroprotective Potential of the Combined Curcuma longa and Rosmarinus Officinalis Ethanol Extract

Background and Objective: Oxidative stress and acetylcholinesterase activities have been implicated in the pathogenesis of neurological conditions leading to memory loss. The bioactive constituents derived from individual plants are sometimes insufficient to provide attractive substantial pharmacological action when compared to a combination of multiple herbs. This study was aimed at investigating the neuroprotective property of the combined ethanolic extract of Rosmarinus officinalis (rosemary) leaf and Curcuma longa (turmeric) rhizome by assessing the antioxidant activity (DPPH, FRAP and NO scavenging ability) and inhibitory activity of cholinergic enzyme (acetylcholinesterase inhibitory activity) of the combined extract in vitro. Materials and Methods: The polyherbal extract was prepared from the combined turmeric and rosemary leaf ethanol extract at a ratio of 3:1. The identification and characterization of bioactive composition of this combined extract was obtained using GC-MS (Gas Chromatography-Mass Spectrometry). Results: Sixty-five bioactive compounds were identified at various concentrations and retention times. The major compounds identified include; 1-Hexacosene (6.46%), Eicosane (4.06%), 6,11-Dimethyl-2,6,10-dodecatrien-1-ol (14.67%), 9-Octadecenoic acid (3.97%) and Trans-13-octadecenoic acid (4.46%). Results also showed that ethanol extract of combined rosemary leaf and turmeric rhizomes (polyherbal), rosemary extract singly, or turmeric extract singly exhibited DPPH radical scavenging abilities, nitric oxide scavenging abilities, reducing power (Fe³⁺-Fe²⁺) and lipid inhibitory activities in concentration-dependent manner. Current study findings indicated that the polyherbal contained a considerably higher DPPH radical scavenging ability, nitric oxide scavenging ability, reducing power (Fe³⁺-Fe²⁺) and lipid inhibitory activity than the single extracts. Furthermore, the polyherbal elicited a higher inhibitory effect on acetylcholinesterase (IC₅₀ = 48.72 µg/mL) than standard drug physostigmine (49.9880 µg/mL). Conclusion: Hence, Curcuma longa rhizome in combination with Rosmarinus officinalis leaf was rich in biologically active components; thus, could be employed to formulate new plant-based pharmaceutical drugs for the management of neurological conditions like Alzheimer’s disease.