L. (Saffron) in Alzheimer's Disease Treatment: Bioactive Effects on Cognitive Impairment

Crocus sativus L. (saffron) appears to own neuroprotective effects on cognitive impairment in patients with Alzheimer's disease (AD). The purpose of this work is to review evidence and mechanisms of saffron-induced therapeutic outcomes and measureable cognitive benefits in AD. The literature was reviewed, and preclinical and clinical studies were identified. In vitro and in vivo preclinical studies were selected according to these criteria: 1) development of saffron pharmacological profile on biological or biophysical endpoints; 2) evaluation of saffron efficacy using animal screens as an AD model, and 3) duration of the studies of at least 3 months. As for the clinical studies, the selection criteria included: 1) patients aged ≥ 60, 2) AD diagnosis according to National Institute on Aging-Alzheimer's Association (NIAAA) criteria, and 3) appropriate procedures to assess cognitive, functional, and clinical status. A total of 1477 studies published until November 2020 were identified during an initial phase, of which 24 met the inclusion criteria and were selected for this review. Seventeen in vitro and in vivo preclinical studies have described the efficacy of saffron on cognitive impairment in animal models of AD, highlighting that crocin appears to be able to regulate glutamate levels, reduce oxidative stress, and modulate Aβ and tau protein aggregation. Only four clinical studies have indicated that the effects of saffron on cognitive impairment were not different from those produced by donepezil and memantine and that it had a better safety profile. Saffron and its compounds should be further investigated in order to consider them a safer alternative in AD treatment.