<p>Thymoquinone (TQ) is known for its antioxidant properties, and although metformin (MM) is known as</p><p>an antidiabetic drug, it is suggested that it reduces neurodegeneration. The study aimed to investigate</p><p>the neuroprotective effects of TQ and MM, particularly when used together, in relation to Parkinson’s</p><p>disease (PD). In the study, sixty-eight male C57BL/6 mice weighing 25–30 g were divided into five</p><p>groups as follows: control, MPTP, MPTPþTQ, MPTPþMM, and MPTPþTQþMM. MM (500 mg/kg, orally)</p><p>and TQ (5 mg/kg, i.p.) were administered for 21 days. Motor coordination and locomotor activities</p><p>were evaluated by the pole test. TOS and TAS analyses were conducted to determine oxidative stress</p><p>levels in the substantia nigra. Dopaminergic degeneration in the substantia nigra was evaluated by</p><p>analyzing Tyrosine hydroxylase (TH). To evaluate the apoptotic pathway, the expression levels of iNOS,</p><p>BDNF, Complex 1, Bax, Bcl-2, Cytochrome C, AIF, and Caspase-3 were examined immunohistochemically.</p><p>Compared to the MPTP-treated group, TQ, MM and MMþTQ treatment provided significant</p><p>improvement in locomotor activity in mice, significantly increased antioxidant activity, significantly</p><p>reduced the expression levels of iNOS, Bax, Cytochrome C, Caspase-3, and AIF, significantly increased</p><p>BDNF, Bcl-2, and Complex 1 expressions, and significantly increased the number of TH positive cells.</p><p>The separate use of TQ and MM exhibits neuroprotective activity, however, we showed that using TQ</p><p>and MM in combination may be more effective. This may provide preclinical evidence supporting the</p><p>therapeutic potential of their combined use for treating PD.</p>