A Natural Additive Alternative to the Cosmetics Industry: Hazelnut and Its Waste Products

Background: Today, individuals tend to use natural products instead of synthetic additives in many areas. The hazelnut tree produces many by-products and fruit. Nuts and their by-products are rich in bioactive compounds. Objectives: This study investigated the biological activities of water and ethanol extracts obtained from hazelnut and its waste products to determine their potential usage in the cosmetic industry. Methods: In this experimental study, disc diffusion test, minimal inhibitory concentration (MIC), minimal bactericidal concentration (MBC), or minimum fungicidal concentration (MFC) were applied to evaluate the antimicrobial potential of the extracts. The sun protection factor (SPF) of the extracts and commercial cream + extract mixtures was determined in vitro. In addition, antimicrobial cream formulations containing hazelnut extracts and Limosilactobacillus fermentum MA-7 probiotic candidate lactic acid bacteria from human milk were developed for the pharmaceutical industry to prevent infections. The good diffusion test was applied against test microorganisms to evaluate antimicrobial activity. Results: The hazelnut husk methanol extract had the highest inhibition zone diameter (19.41 mm) against Yersinia ruckeri. The MIC, MBC, or MFC of the extracts ranged from 1.25 to > 40 µg/µL. The SPF values of the extracts (range: 6.85-27.64) and commercial cream + extract (range: 11.92-26.28) mixtures were determined in vitro to obtain their potential use in sunscreens. The cream groups containing hazelnut extracts and probiotics showed a high antimicrobial effect on the tested microorganisms. The results of statistical analysis indicated that the cream + extract + probiotic pellet + probiotic supernatant group was statistically significant (P < 0.05) compared to other test groups. Conclusions: The results showed that hazelnuts and their by-products have the potential to be used as a natural source of antimicrobials. Hazelnut and its by-products can be an alternative to synthetic antimicrobials and sunscreens in the cosmetic industry as a natural bioactive substance. In addition, it might contribute to the country’s economy by evaluating hazelnuts and their waste and by-products resulting from their processing in the cosmetic industry.