Parkinson's disease (PD) is a second common neurodegenerative disease. More than 6 million individuals worldwide have Parkinson disease. No disease-modifying pharmacologic treatments are available. Current medical treatment is symptomatic, focused on improvement in motor (eg, tremor, rigidity, bradykinesia) and nonmotor (eg, constipation, cognition, mood, sleep) signs and symptoms. Accumulating evidence suggests the important role for inflammation and oxidative stress in the pathogenesis of PD. Sulforaphane extracted from broccoli sprout is an agent with potent anti-oxidant and anti-inflammatory activity. Previous studies suggested sulforaphane is useful in dopaminergic neuron survival. In this study, the investigator attempts to evaluate the efficacy and safety of sulforaphane in PD patients.

The study will recruit 100 PD patients, and then these patients will be randomized to sulforaphane group or placebo group (50 patients per arm) for 24 weeks clinic trial. Participants will receive 24 weeks of either sulforaphane or placebo per day, in addition to the existing treatment. Baseline assessments include demographics, a comprehensive medical history, anthropometric measurements (weight and height), physical examination, and lab work. The motor symptoms and cognitive function will be assessed by the Unified Parkinson's Disease Rating Scale (UPDRS) and MATRICS Consensus Cognitive Battery #MCCB#, respectively, at baseline, week 12 and week 24. The cranial MRI is examined at baseline and repeated at week 24. The primary outcomes will be the cognitive function improvement. Secondary outcomes include motor symptoms, biological data, MRI, safety and tolerability. During the study period, safety index including blood routine, liver and kidney function and adverse reactions report will be recorded.

Inclusion Criteria:

1. Age range from 40 to 75, regardless of ethnic group or gender;
2. Meeting the criteria for clinically established PD (2015) by Movement Disorder Association（MDS）; duration < 5 years;
3. Mini-Mental State Examination (MMSE) ≤ 27 points, but ≥20 points. Hoehn-Yahr stage ≤ 3;
4. Before enrollment, patients should take a stable dose of dopamine-based therapies drugs;
5. No obvious visual or hearing impairment;
6. More than 9 years of education;
7. Patients understand and comply with the study procedure, and are able to complete all tests and examinations required by the program. Sign the informed consent.

Exclusion Criteria:

1. Patients who have received globus pallidotomy, thalamotomy, deep brain stimulation (DBS), or stem cell therapy;
2. Other causes of parkinsonism: medications (e.g., metoclopramide, flunarizine), metabolic neurogenetic disorders (e.g., Wilson's disease), encephalitis, cerebrovascular diseases, or degenerative disorders (e.g., progressive supranuclear palsy);
3. Central nervous system diseases (including stroke, optic neuromyelitis, Parkinson's disease, epilepsy, etc.);
4. Have liver, kidney function insufficiency;
5. Unstable or severe diseases of the heart, lung, liver, kidney and hematopoietic system according to the judgment of the researchers;
6. Participated in other clinical trials within 3 months before screening visit;
7. Other conditions are unsuitable for participating in this study according to the judgement of researchers.