Determination of Bioactive Compounds, Antioxidant Capacity, Safety Assessment, and Antimicrobial Effect of Tristerix corymbosus Extracts

Quitral (Tristerix corymbosus), a Chilean and Argentine parasitic mistletoe, is traditionally used by Mapuche natives to treat stomach ulcers, nervous disorders, and cholesterol reduction, although scientific support is scarce. Methanolic and chloroform extracts from its leaves and stems were prepared. Chemical analysis included antioxidant capacity assays (ORAC-FL and DPPH) and chromatographic determinations. The antimicrobial activity was tested against nine bacteria and two yeast strains. Additionally, cytotoxicity (hemolysis) and toxicity (against Caenorhabditis elegans) assays were performed. The results revealed that the methanolic leaf extracts had the highest ORAC-FL value, with DPPH assays showing solvent-dependent differences. Thirty-one compounds were tentatively identified, of which 61% were phenolic compounds, primarily flavonoids like quercetin and its derivatives. Antimicrobial results showed activity against Gram-positive bacteria (Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, and Enterococcus faecalis), but not against yeast Candida guillermondii and Candida tropicalis. Methanolic extracts induced dose-dependent erythrocyte hemolysis, while chloroform extracts showed no relevant cytotoxicity. Toxicity against Caenorhabditis elegans was also dose-dependent for methanolic extracts; leaf extract reduced survival at 50 mg mL−1 after 24 h. These findings partially validate some traditional uses, highlight the importance of solvent polarity in extraction and biological effects, and establish quitral as a flavonoid source.