Neuroprotective Potential of Thai Cinnamon (Cinnamomum bejolghota) Bark Extracts against Oxidative Stress-Induced Neurotoxicity in SH-SY5Y Neuroblastoma Cells

Neurodegenerative diseases are associated with oxidative stress, which may be alleviated by antioxidant-rich plant compounds such as cinnamon. This study investigates the neuroprotective effects of Thai cinnamon bark (Cinnamomum bejolghota) extracts, in both powder and essential oil forms, against H2O2-induced neurotoxicity in SH-SY5Y neuroblastoma cells. The extracts were analyzed for their phenolic and flavonoid content as well as their antioxidant activities using DPPH, FRAP, and ABTS assays. Neurotoxicity and neuroprotection were assessed via MTT, LDH, TBARs, and ROS assays. The powder extract exhibited a high phenolic content (1,275.25 ± 24.07 mg GAE/g) and demonstrated stronger antioxidant activity across all assays compared to the oil form. DPPH and ABTS assays revealed IC50 values of 195.80 µg/mL and 35.55 µg/mL, respectively, for the powder extract, while the FRAP assay confirmed its dose-dependent scavenging effects (p ≤ 0.01). Conversely, the oil extract exhibited low flavonoid content (3.05 ± 3.82 mg QE/g), weaker antioxidant activity, and no significant effects at any tested concentration (p ≤ 0.01). MTT assays confirmed the safety of powder concentrations (100–1,000 µg/mL) for neurons, whereas oil concentrations as low as 80 µg/mL reduced cell survival to 68.85%. Both extracts displayed neuroprotective properties against oxidative stress, with the powder extract demonstrating superior efficacy. At 1,000 µg/mL, the powder extract significantly reduced LDH activity, ROS levels, and lipid peroxidation (p ≤ 0.01). These findings suggest that Thai cinnamon powder, when incorporated into food or beverages, may help prevent neurodegeneration caused by oxidative stress. Further studies are needed to optimize its therapeutic potential.