Coffee is one of the most popular beverages in the world. Europe has the highest consumption of green coffee beans and generates about 3.4 million tons of spent coffee grounds (SCGs) every year. Despite the long and complex processing of coffee beans, SCGs still contain numerous valuable compounds, including antioxidants. These compounds have a beneficial influence on various aspects of human health and even anticancer activity. Cancer is one of the leading causes of death worldwide. The skin, as the largest organ of our body, is exposed to dangerous external factors such as UV, which has been defined as the main cause of skin cancers. This research aims to investigate the possible usage of a full antioxidant extract from SCGs, as well as single compounds like caffeine and chlorogenic acid. in anti-cancer therapies.

The antioxidant extract, caffeine and chlorogenic acid were obtained by way of an optimized extraction process. The influence of the obtained compounds and the entire extract on normal and cancer skin cell lines was checked. The effect on melanoma cells at various metastatic stages and on squamous-cell carcinoma was tested. The impact of the tested compounds was assessed using cytotoxicity tests such as FDA/PI, MTT and resazurin staining.

The impact of each tested extract, along with caffeine and chlorogenic acid, varied depending on the cell lines analyzed. Notably, differences were observed even among melanoma cells at distinct metastatic stages. For instance, the ethanolic extract demonstrated a suppressive effect on the metabolic activity of primary melanoma cells.

SCGs are a remarkable source of various antioxidants with possible applications in various fields. This study allows us to gain unique knowledge about the impact of the antioxidants contained in SCGs on normal and cancerous skin cells.

This work was supported by the National Science Centre (Poland) Grants no.2023/49/N/NZ5/03578.