When it comes to the development of new active ingredients for cosmetics, biodiversity is a rich source for inspiration that must be tapped in a sustainable manner to cause no social nor ecological damage. Agri-food by-products are therefore more and more considered as available biomass that can be reused to extract their maximum value to produce new cosmetic ingredients before returning to the biosphere. The process to transform plant waste materials into powerful cosmetic actives is thoroughly described in the present paper via the example of the design of a liquid anti-aging ingredient based on a Prunus domestica L. extract obtained by maceration of plums' dried leaves in propylene glycol. The subsequent development of an SPE (solid-phase extraction) methodology used to remove the propylene glycol to get access to the extracted molecules is thoroughly described as a means to follow the stability of the ingredient over time once formulated into a finished product.Cosmetics 2019, 6, 8 2 of 21 for the cosmetics sector [3,4]. These new environmentally-friendly habits offer valuable advantages: (a) reusing such "waste" material to get as much value as possible from every resource, which offers a unprecedented degree of traceability on the materials' origin as sourcing channels already exist and are secured [5]; (b) developing the potential of waste to be used as raw material enables the diversification of value chains for one single market segment and may subsequently imply the growth of farmers/producers' incomes, hence strengthening those sourcing channels; and (c) they constitute furthermore fantastic communication opportunities and with the appropriate marketing strategy, cosmetic brands can really connect with customers through their mutual responsibility toward the environment preservation and gain new market shares.This article presents a procedure to design efficient cosmetic ingredients while meeting the challenging consumer's demands for sustainability, naturality, transparency and traceability.In order to integrate those sustainability values into our process of ingredients' development and to take advantage of the "green" phenomenon, we accessed a wide range of by-products that were extracted using several solvents. Given the promising results already shown by our research team regarding leaves of Prunus domestica L. (Rosaceae) [6], special attention was brought to the potentiality to create valorisation channels for by-products of the plum industry (food usages mainly: fresh, canned or dried fruits, more processed products, etc.).Prunus domestica L. is a species of flowering plant that includes many varieties of plum trees. P. domestica is the most commonly grown plum in Europe over a wide range of climatic conditions: the fruits constitute a first-rate dessert, and are appreciated to produce tarts, eau de vie, as well as dried plums, known as prunes.The Blue Perdrigon (also known as Violet Perdrigon, Perdrigon Viollette or Brignoles Violette) is a very old plum variety cultivated in the Provence regio...