Pistacia lentiscus L. is an evergreen shrub or tree-like plant named as ‘mastic tree’. The phytochemical studies of Chios mastic gum have revealed that it is a complex natural product comprising several organic ingredients like natural polymers, essential oils and triterpenic compounds. Triterpenes are the main components of mastic gum, and they are thought to be responsible for important biological activities such as anti-cancer, anti-ulcer, cytotoxic, antidiabetic, and anti-inflammatory. Within the scope of this thesis, mastic gum collected from the mastic trees (Pistacia lentiscus var. chia) grown on the Karaburun peninsula of İzmir was investigated to reveal its phytochemical composition and neuroprotective effects of the isolates. Isolation and purification studies utilizing chromatographic methods are followed by structural elucidation of the isolates by spectroscopic methods (1D NMR, 2D NMR, MS and X-RAY). Detailed analysis of the obtained spectra helped us to establish structures of 14 molecules possessing triterpenic skeleton, and two of them turned out to be undescribed compounds. The bioactivity of selected compounds was screened for their neuroprotective effects against H2O2 induced oxidative stress on differentiated and undifferentiated SH-SY5Y cells. Two compounds showed neuroprotective effects against H2O2-induced cell death on undifferentiated SH-SY5Y cells at 5 and 10 μM concentrations, while the other compounds either showed little or no effect. This study provides promising new insights into the use of mastic gum or its components in the treatment of neurodegenerative diseases.