Abstract Objective The primary objective of this study was to investigate the biological activities of freeze‐dried Ganoderma lucidum (Reishi) extract obtained from hazelnut pruning waste and to compare its antioxidant, tyrosinase inhibitory and cytotoxic properties with two widely used cosmetic actives—argireline peptide and α‐arbutin. Additionally, the study aimed to develop a topical cream formulation containing Reishi extract and to assess its microbiological safety, preservative efficacy and physicochemical stability under controlled environmental conditions. By integrating bioactivity evaluation with formulation performance, the research sought to determine the potential applicability of Reishi extract as a natural and multifunctional cosmetic ingredient suitable for anti‐aging and skin‐brightening applications. Methods The antioxidant capacity of Reishi extract, argireline peptide and α‐arbutin was determined using a copper(II)‐based total antioxidant capacity assay. Tyrosinase inhibitory activity was measured with human tyrosinase sourced from MNT‐1 melanoma cells, while cytotoxicity and safe dose limits were determined in HaCaT human keratinocyte cells via the AlamarBlue® method. A topical cream formulation was prepared using a multi‐phase emulsification technique and characterized physicochemically. Microbiological safety was assessed according to Turkish Cosmetic Regulations, and preservative efficacy was determined through challenge testing. Stability assessments included temperature cycling, long‐term storage at different temperatures and centrifugation tests, monitoring visual, physicochemical and microbiological parameters over a three‐month period. Results Reishi extract demonstrated 861 μmol TE/g antioxidant activity, 30% tyrosinase inhibition and a broader safety margin compared with argireline peptide and α‐arbutin, which exhibited cytotoxicity at lower concentrations. The formulated cream retained a skin‐compatible pH and stable viscosity, while showing no signs of phase separation, colour change or integrity loss under all storage conditions. Microbiological analysis confirmed microbial counts below regulatory limits, and challenge testing revealed rapid log reductions in all tested microorganisms, satisfying the acceptance criteria for preservative efficacy. Stability studies supported the physical robustness and microbiological safety of the final product throughout the evaluation period. Conclusion Overall, the findings highlight Reishi extract as a bioactive‐rich, safe and stable natural ingredient with strong potential for incorporation into cosmetic formulations. Its antioxidant performance, moderate tyrosinase inhibition and compatibility within the cream matrix support its use in multifunctional anti‐aging and skin‐brightening products.
Küçük et al. (Mon,) studied this question.