An NMR-based metabolomics strategy for adulteration detection of natural resins: Application to Chios mastic gum

Chios mastic gum (CMG), the resin from Pistacia lentiscus L. var. Chia, is a valuable natural product with a long history of therapeutic use and significant economic impact. However, its authenticity is increasingly challenged by adulteration with chemically similar resins, particularly Pistacia atlantica. This study presents a robust ¹H NMR-based metabolomics approach combined with principal component analysis (PCA) to authenticate CMG and distinguish it from other resins. A total of 131 resin samples—including 71 authentic CMG samples from four Chios subregions—were analyzed. A distinct metabolic signature for CMG was revealed, primarily characterized by high levels of masticadienonic acid (MNA), isomasticadienonic acid (IMNA), oleanonic aldehyde, and cis-1,4-poly-β-myrcene. The resulting chemometric model effectively differentiated CMG from adulterants, including Iranian mastic gum (IMG) and aged CMG, and identified mislabeled commercial samples. Two authentication indices (MA Index-1 and MA Index-2) were developed based on key metabolite concentrations and their ratios, providing a quantifiable, reproducible framework for CMG quality control. This method enables rapid, non-destructive authentication without extensive sample preparation or reference standards, offering a valuable tool for safeguarding the integrity of CMG in commercial and regulatory settings.