Upcycling Roman Chamomile Hydrolate and Apple Pomace Agri-Wastes into Sustainable Cosmetic Ingredients

The aim of this study was to evaluate the potential of selected agri-food by-products-apple pomace extract from Malus domestica cv. 'Grochówka' and Roman chamomile (Chamaemelum nobile L.) hydrolate-as functional, sustainable ingredients for cosmetic applications. The work focused on their chemical composition, biological activity, formulation performance, and in vivo effects on skin condition. Volatile compounds, phenolic acids, and triterpenoids were analyzed by GC-MS, while total phenolic content, antioxidant capacity, and enzyme inhibitory activity were evaluated in vitro. An oil-in-water emulsion containing the by-products was formulated and, in a 14-day split-face study, assessed for its effects on skin hydration, elasticity, inflammation, sensitivity, pore visibility, and melanin index. Biochemical analyses have shown that chamomile hydrolate is characterized by very low antioxidant activity (DPPH 5.0 ± 1.25%, FRAP 0%) and weak protease inhibition (9.70 ± 1.84%). In contrast, apple extract contained a significant amount of polyphenols (23.94 ± 0.3 mg GAE/g) and showed strong antioxidant properties (DPPH 79.4 ± 2.12%, FRAP 70.56 ± 2.23%; IC₅₀ = 21.5 ± 0.196 mg/mL), which confirms the dominant role of phenolic compounds in its biological activity. This extract also demonstrated significant protease inhibition (60.88 ± 2.35%; IC₅₀ = 15.02 ± 0.47 mg/mL), while its lipase inhibition activity was moderate (10%), which may be beneficial from a cosmetic perspective. The obtained results indicate that apple extract is a valuable raw material with multifaceted biological potential. Overall, the results demonstrate that apple pomace extract and chamomile hydrolate can be effectively valorized as bioactive cosmetic ingredients, supporting both skin health benefits and circular economy principles in sustainable cosmetic formulation.