Conjugation of Glycine max (L.) Merrill Oligopeptide with Monosaccharides: A Novel Approach for Stability and Efficacy in Cosmeceutical Applications

Background/Objectives: Conjugation techniques are increasingly valued in food chemistry for enhancing sensory properties, nutritional profiles, and bioactivity, with potential applications in cosmeceuticals. This study aimed to investigate the potential of Glycine max (L.) Merrill oligopeptide–monosaccharide conjugates as active ingredients in cosmeceuticals, emphasizing their biological activities and stability. Methods: G. max isolate was prepared and subsequently hydrolyzed using alcalase to obtain the oligopeptide (OP). The OP was then conjugated with allulose (AL) or mannose (MN) through a controlled humid-dry heating process to produce the conjugates, OPA and OPM, respectively. Their biological activities, including antioxidant, anti-tyrosinase, anti-collagenase, anti-elastase, and anti-hyaluronidase properties, were assessed and compared to the individual components. Additionally, the irritation potential was evaluated using the hen’s egg test on chorioallantoic membrane (HET-CAM). The stability was examined under varying pH levels, temperatures, and light conditions based on their biological activity profiles. Results: OPA demonstrated the highest antioxidant activity, showing the lowest DPPH• IC50 value of 198.6 ± 2.7 µg/mL along with a strong ferric reducing power of 1.37 ± 0.04 µg FeSO4/g sample. Besides, OPM showed superior tyrosinase inhibition on both L-tyrosine and L-DOPA substrates, highlighting its potential for skin whitening. Both OPA and OPM significantly enhanced collagenase inhibition, supporting their anti-aging potential. All samples were non-irritating in the HET-CAM test. The conjugates (OPA and OPM) demonstrated enhanced stability against pH, heat, and light compared to OP, AL, and MN. Conclusions: Oligopeptide–monosaccharide conjugation not only improved bioactivity but also enhanced biological stability, suggesting their potential for use in cosmeceutical applications.