Comprehensive analysis of elemental profiles, caffeine and chlorogenic acid contents, antioxidant activities, and isotope ratios in Thai single-origin green coffee beans

• Robusta had higher caffeine and chlorogenic acid than Arabica. • Robusta showed stronger antioxidant activity (TPC, DPPH, FRAP). • Potassium was the major element; mineral profiles varied by variety. • δ¹³C and δ¹⁵N values distinguished varieties and farming practices. • Biochemical and isotopic markers enabled coffee origin traceability. Coffee is a globally consumed beverage with increasing interest in its chemical composition and origin traceability. This study analyzed the chemical, antioxidant, elemental, and isotopic characteristics of Arabica and Robusta green coffee beans from 31 cultivation regions in Thailand. High-performance liquid chromatography (HPLC) revealed that Robusta beans had significantly higher concentrations of caffeine (15.57 mg/g) and chlorogenic acid (47.71 mg/g) compared to Arabica beans (11.76 mg/g and 40.9 mg/g, respectively). Spectrophotometric assays showed that Robusta samples exhibited significantly higher total phenolic content (TPC) (55.19 mg GAE/g), 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity (DPPH) (51.42 mg AAE/g), and ferric reducing antioxidant power (FRAP) (551.17 µmol FeSO₄/g) activities, indicating a stronger antioxidant capacity than Arabica. X-ray fluorescence (XRF) analysis identified potassium as the predominant element and revealed significant differences in the elemental compositions between the two varieties, likely influenced by geographic and agricultural factors. Isotope ratio mass spectrometry (IRMS) showed distinct δ¹⁵N values for Robusta (2.79‰) and Arabica (1.89‰), suggesting variations in fertilizer practices, while the δ¹³C values confirmed that both varieties followed the C3 photosynthetic pathway. Strong correlations were observed between TPC, DPPH, and FRAP as well as between caffeine and chlorogenic acid content. Hierarchical clustering grouped the samples based on their biochemical and isotopic profiles, supporting the use of these markers for coffee authenticity verification and origin traceability. The findings provided valuable insights into the biochemical diversity and geographic differentiation of Thai green coffee beans.