South Brazilian Amber Propolis: Chemical Profile, and Antioxidant, Antimicrobial and Antileukemic Activities.

This study introduces "amber propolis," a unique variety from the Pampa biome in southern Brazil, characterized by a distinct chemical fingerprint and high biological potency. The composition was comprehensively analyzed via GC-MS and LC-MS/MS; biological activity was evaluated through antimicrobial (Staphylococcus aureus and Escherichia coli) and antileukemic screenings against K562, Jurkat, and U937 cell lines. Results revealed a terpenoid-dominant profile (comprising 60-70% of identified features) despite a lower flavonoid abundance compared to traditional reference samples. Amber propolis exhibited significantly higher antibacterial activity against S. aureus than green propolis, whereas all varieties showed similar dose-dependent inhibition of E. coli, reaching complete growth suppression at 500 µg/mL. Notably, it acted as a potent antileukemic agent, inducing rapid apoptosis starting at 12 h in Jurkat and U937 cell lines, and at 24 h for K562 cells, while concomitantly triggering G2/M cell cycle arrest. Unlike the variable responses observed for green and red propolis across lineages, amber propolis demonstrated a uniquely uniform cytotoxic effect, suggesting the involvement of distinct, conserved molecular mechanisms. These findings challenge the prevailing paradigm associating propolis bioactivity primarily with phenolic abundance. Collectively, this study establishes amber propolis as a chemically distinct and biologically active variety with strong potential for pharmaceutical and nutraceutical applications, supporting its future valorization and geographical indication within the Brazilian Pampa biome.