Use of at least an active ingredient of natural peptide, obtained from hydrolysis of flax protein ( Linumgenus), in a cosmetic composition or for preparing a pharmaceutical composition, to activate cytochrome c and stimulate mitochondria, is claimed. An independent claim is included for a process for cosmetic treatment to stimulate defense and protect skin and integument from external aggregation, comprising applying the composition on the skin and integument. ACTIVITY : Dermatological. MECHANISM OF ACTION : None given.