Biological Investigation of Spent Coffee Ground for Potential Cosmeceutical Applications

The global shift towards coffee consumption has resulted in a significant increase in spent coffee grounds (SCG) waste. The potential biological activities of SCG, however, remain underexplored. This research investigated the cosmeceutical application potential of SCG, exploring the phytochemical composition, radical scavenging activity, anti-melanogenic activity, and photoprotective properties of SCG extracts obtained from both conventional and cold brewing methods. SCGs were extracted using ethanol, ethyl acetate, and hexane; after conventional and cold brewing methods, revealing differences in phytochemical yields. Ethyl acetate and ethanol extractions in both conventional and cold brew SCG exhibited the highest total phenolic content. Conversely, there was no difference in total steroidal content among different solvents. Cold brew SCG ethanol extract presents the highest antioxidant capacity, owing to its ability to scavenge neutral radical [1,1-diphenyl-2-picrylhydrazyl] (DPPH^•), cation radical [2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)] (ABTS^+•), and metal ions, followed by the cold brew SCG ethyl acetate extract. Nevertheless, none of the extracts exhibited inhibitory activity against mushroom tyrosinase, suggestive of the absence of anti-melanogenic activity. UV absorption spectra indicated relatively effective UVB protection in cold brew ethyl acetate and ethanol extracts, with determined Sun Protection Factor (SPF) of 7.74 and 5.39, respectively. Spearman correlation analysis revealed significant correlations between total phenolic content and radical scavenging assays (p < 0.05). In summary, this study underscores the potential of cold brew SCG ethanolic and ethyl acetate extracts as a sustainable source of cosmeceutical ingredients, offering good antioxidant and mild photoprotective benefits for skincare formulations and sustainable waste management.