Effects of Sulforaphane in Patients With Prodromal to Mild Alzheimer's Disease

Inclusion Criteria: * 1\. Age range from 50 to 75 (including 50 and 75 years old), regardless of ethnic group or gender; * 2\. The subjects should be able to complete the cognitive ability measurement and other tests specified in the protocol; * 3\. Meeting the criteria for likely Alzheimer's Disease （AD） dementia (2011) by National Institute of Neurological Disorders and Strokes - Alzheimer's Disease and Related Diseases Association（NINCDS-ADRDA）; * 4\. Patients with mild dementia: the total score of Mini-Mental State Examination (MMSE) : ≥22 points; Clinical Dementia Rating scale （CDR）score \> or equal to 0.5 and \< or equal to1；The MMSE score provides evidence of mild disease severity and the CDR-GS score indicates that the patients have noticeable amnestic (pAD) or cognitive and functional (mAD) deficits * 5\. The total score of the Hachinski Ischemic Score （HIS ）was \< 4. * 6\. Hamilton depression scale (17 items) total score ≤7 points; * 7\. Brain MRI shows a high likelihood of AD; * 8\. Before enrollment, patients should take a stable dose of dementia drugs (donepezil 5mg) ≥8 weeks; * 9\. The expected survival time is \> 1 year; * 10\. Subjects should have a stable and reliable caregiver, or at least have frequent contact with the caregiver (at least 3 days per week and at least 2 hours per day), who will help patients participate in the whole study; Caregivers must accompany the subjects to the visit and assist in completing the relevant scale. Exclusion Criteria: * 1\. Refuse to sign the inform consent form; * 2\. Other causes of dementia: known vascular, central nervous system infection ,Parkinson's disease, traumatic brain dementia, other physical and chemical factors; serious body disease , intracranial space-occupying lesions, endocrine system disease, such as thyroid disease, and a lack of vitamin B12, folic acid, or any other known causes of dementia. * 3\. Central nervous system diseases (including stroke, optic neuromyelitis, Parkinson's disease, epilepsy, etc.); * 4\. Obvious positive signs of nervous system examination; * 5\. Psychotic patients, including schizophrenia or other disorders with bipolar disorder, major depression or delirium; * 6\. Uncontrolled hypertension or hypotension during screening: systolic blood pressure ≥180（millimetres of mercury ）mmHg or \< 90mmhg, or diastolic blood pressure ≥120mmHg or \< 60mmhg; * 7\. Unstable or severe diseases of the heart, lung, liver, kidney and hematopoietic system according to the judgment of the researchers; * 8\. Patients with incurable visual and auditory disorders that cannot complete neuropsychological tests and scales; * 9\. Female subjects who are positive in pregnancy test or breast-feeding and who cannot take effective contraceptive measures or have a birth plan; * 10\. Severe allergy, non-allergic drug reaction or multi-drug allergy history; * 11\. Participated in other clinical trials within 3 months before screening visit; * 12\. Taking any health care products related to brain and brain improvement currently and failing to keep the promise to stop using the above products; * 13\. Other conditions are unsuitable for participating in this study according to the judgement of researchers.