The major health problems observed all over the world are often associated to age since people are living longer [
1]. In recent years, marine natural products have become one of the most important sources of new compounds potentially useful in the treatment of age-related diseases, such as cancer, neurodegenerative and cardiovascular diseases, metabolic syndrome and many others [
2,
3,
4].
Spirulina (cyanobacteria:
Arthrospira platensis) is a photosynthetic Gram-negative filamentous bacterium that grows naturally in alkaline, brackish, marine and fresh waters [
5], but it is also commercially produced in large outdoor or greenhouse ponds under controlled conditions [
6]. In recent years,
A. platensis has attracted more and more attention as a potential source of pharmaceutical compounds. Indeed, this cyanobacterium is a source of many, but only partially identified and purified compounds with potential health benefits and activities. It is particularly rich in proteins (65% to 70%) as well as phycocyanin (PC), vitamins, beta-carotene, polyunsaturated fatty acids, minerals, especially iron, polysaccharides and others [
7]. Phycocyanin, which accounts for up to 20% of this cyanobacterium’s dry weight, is the association of proteins of the phycobiliprotein family and water-soluble pigments of photosynthesis, the phycocyanobilins. Phycocyanin consists of α and β subunits whose ratio is usually 1:1; the molecular weight of the α and β subunits is 16.3kD and 18.9kD, respectively [
8]. The determination of the purity of phycocyanin is based on the absorbance ratio A620/A280; the absorbance at 620nm corresponds to the phycocyanin present in the preparation (it is proportional to the quantity of pigment), while the absorbance at 280nm corresponds to the total proteins (it is proportional to the proteins in solution). When A620/A280 is > 0.7 phycocyanin is considered edible, when 0.7≤A620/A280≤3.9 the phycocyanin is considered reagent grade and finally, when A620/A280 is ≥4.0 the phycocyanin is considered analysis level [
9]. Phycocyanin is considered responsible for
A. platensis anti-cancer, anti-inflammatory and antioxidant activities [
10,
11]. In particular, phycocyanin has been shown to reduce oxidative stress in both yeast and mammals [
12,
13]. Moreover, data in literature showed that the antioxidant properties of phycocyanin might arise from both radical-scavenging and metal chelation [
14]. Since, ROS are considered important factors causing aging, the anti-aging activity of phycocyanin has been investigated. However, the question how exactly phycocyanin works against aging remains elusive. In particular, the intracellular mechanism of action of PC has been poorly studied and most of its possible targets are still unclear [
8,
15].
In this paper, we used the yeast
S. cerevisiae as a model organism to study the anti-aging properties of PC purified from the cyanobacterium
A. platensis. We show that phycocyanin has a powerful anti-aging effect, greatly extending the chronological life span of yeast cells grown in SD medium, under both calorie restriction (CR) conditions (0.2% glucose) or non-CR conditions (2% glucose), Interestingly, we show an increase in ROS level, which does not correlate with cell death measured counting the colony forming units over time, when cells are grown in the presence of phycocyanin. This result might suggest that phycocyanin promotes longevity by inducing hormesis [
19,
20,
21], an adaptive response to a variety of stresses according to which low doses of ROS act as essential signaling molecules to promote metabolic health and longevity.