Comparative analysis of curcuminoid content, antioxidant capacity, and target-specific molecular docking of turmeric extracts sourced from Thailand

Abstract

Curcuminoids are the active compounds richest in turmeric rhizomes (Curcuma longa L.), comprising curcumin I, demethoxycurcumin (curcumin II), and bisdemethoxycurcumin (curcumin III). This study hypothesized that particular curcumin derivatives could mitigate oxidative stress and inflammation response by targeting specific inflammatory mediators. Therefore, this study aimed to quantify the concentrations of these curcuminoid forms in local turmeric extracts from Thailand. Subsequently, the study analyzed their in vitro antioxidant properties, alongside molecular docking and dynamics simulations targeting key oxidative stress- and inflammation-related proteins. Samples were collected from three representative cultivated areas in Thailand: the eastern, southern, and northern regions. The ethanolic extracts from all samples exhibited relatively high total curcuminoid content (eastern: 15.1 %, southern: 25.9 %, and northern: 31.6 % w/w in extract), as determined by high-performance liquid chromatography. Curcumin I emerged as the predominant variant, followed closely by curcumin II and III. The ethanolic extracts from the three cultural areas demonstrated significant antioxidant activity, as assessed by ORAC, FRAP, and DPPH assays. Among the three curcuminoids, curcumin III exhibited the strongest predicted binding affinities in molecular docking studies toward antioxidant and anti-inflammatory targets, including 5-LOX, NRF2, IKK1, NF-κB, and NOX4. Molecular dynamics simulations corroborated these findings, revealing that curcumin III formed the most stable complexes, particularly with IKK1, as indicated by low RMSD values (2–3 Å), and high hydrogen bond occupancy. Thus, curcumin III exhibits potential in silico inhibition of inflammatory mediators, supporting its promise as a natural compound for antioxidant and anti-inflammatory nutraceutical development.