Natural toxicants, particularly methoxy
phenols (MPs) generated by wildfire
lignin, can accumulate in the environment, and cause serious health hazards in living organisms. Although the toxicity of MPs such as
guaiacol and
catechol has recently been described, there is minimal evidence of ecotoxicological effects of
syringol. As a result, this study focuses on determining the toxicity by evaluating the cytotoxic and teratogenic effects of
syringol in vitro and in vivo in human embryonic kidney (HEK-293) cells and zebrafish embryos, respectively. The ecotoxicity of
syringol was predicted to be 63.8 mg/L using the ECOSAR (ECOlogical Structure Activity Relationship) prediction tool, and molecular docking analysis was used to determine the interaction and binding affinities of
syringol with human apoptotic
proteins in silico. In HEK-293 cells, exposure of
syringol (0.5-2 mg/L) has induced cytotoxicity in a concentration-dependent manner. In zebrafish larvae, exposure of
syringol (0.5-2 mg/L) has induced dose-dependent embryo toxic effects (or growth abnormalities such as yolk sac
edema, pericardial
edema, skeletal abnormality, and
hyperemia), and changes in growth morphometrics (head height, eye, yolk sac, and pericardial area, heart rate) in particular, the heart rate of larvae was found to be significantly decreased (p<0.001). After a 4-day experimental trial, the accumulated concentration of
syringol in zebrafish larvae was confirmed both qualitatively (HPLC-MS - High Performance Liquid Chromatography-Mass spectrometry) and quantitatively (LC-QTOF-HRMS - Liquid Chromatography-Quadrupolar Time of Flight-High Resolution Mass spectrometry). The
craniofacial abnormalities induced by
syringol exposure (0.5-2 mg/L) were detected as anomalies in cartilaginous development and locomotor deficits using
alcian blue staining and locomotor analyses, respectively. Significant increase in oxidative stress parameters (including
reactive oxygen species generation, lipid peroxidation,
superoxide dismutase,
catalase,
lactate dehydrogenase and
nitric oxide production) (p<0.001) and substantial decrease in
glutathione levels were observed (p<0.05) in
syringol exposed zebrafish larvae through enzymatic analysis. Additionally, through
acridine orange staining and gene expression analyses,
syringol (2 mg/L) was found to activate apoptosis in zebrafish larvae. Considering the cytotoxic, embryotoxic (teratogenicity), and oxidative stress-related apoptotic effects of
syringol in the zebrafish model,
syringol has the potential to emerge as a potent environmental toxicant posing serious health hazards in many living systems; however, further research on its toxicological effects on the actual ecosystem and in higher animal models is required to confirm its consequences.