Contents of Bioactive Compounds and Antioxidant Activities of Commercial Dried Noni and Noni Powder

This study aimed to evaluate the functional compound content and antioxidant activity of eight commercially available dried and powdered noni (Morinda citrifolia) products (NP1-8).Quantitative analysis of key bioactive compounds (scopoletin, quercetin, and rutin) revealed significant variation among samples, with NP3 showing the highest concentrations, while NP7 contained the lowest or undetectable levels.Moreover, six lignan compounds (secoisolariciresinol, matairesinol, pinoresinol, lariciresinol, syringaresinol, and medioresinol) were quantified, showing marked variation among the NP samples, with NP3-NP6 exhibiting relatively high total lignan content.In contrast, medioresinol was undetectable in all samples.Total polyphenol content (TPC) and total flavonoid content (TFC) were also highest in NP1 and NP3, correlating strongly with their 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities.Notably, NP3 exhibited significant cytoprotective effects in tert-butyl hydroperoxide-induced oxidative stress in HepG2 cells, indicating biologically relevant antioxidant activity.Pearson's correlation analysis showed strong positive correlations among all variables, with the highest correlation observed between ABTS and DPPH radical scavenging activities (r=0.996,P<0.01).Among the functional compounds, TFC showed a near-perfect correlation with DPPH radical scavenging activity (r=0.977,P<0.01).These findings suggest that the antioxidant potential of noni powder is closely linked to its polyphenol and flavonoid content, and highlight the need for standardization and quality control in commercial noni products.The results provide valuable baseline data for developing highly functional noni-based products and evaluating their health benefits.