Caffeic acid is an organic compound that is classified as a hydroxycinnamic acid. Caffeic acid is naturally found in many agricultural products, such as fruit, vegetables, wine, olive oil, and coffee, and therefore, significantly present in human diet. Caffeic acid has been reported to have a wide variety of biological activities, including antioxidants, antithrombosis, antihypertensive, antifibrosis, antiviral and anti-tumor properties. Caffeic acid can be effectively employed as a natural antioxidant in various food products such as oils. Caffeic acid exhibits potent anticancer effect in HT-1080 cell line and that it may be used as an anticancer agent. Caffeic acid showed neuroprotective action against oxidative and DNA damage produced in the kindling epilepsy model, although they did not produce antiepileptogenic effect in vivo. Caffeic acid was effective in patients with primary immune thrombocytopenia. Detected in clinical trial caffeic acid-related adverse events were: mild nausea and elevation of liver enzymes.

Kojic acid was first discovered in Japan in 1907. Kojic acid is a chelation agent produced by several species of fungi, especially Aspergillus oryzae, which has the Japanese common name koji. Kojic acid is a by-product in the fermentation process of malting rice, for use in the manufacturing of sake, the Japanese rice wine. It is a mild inhibitor of the formation of pigment in plant and animal tissues, and is used in food and cosmetics to preserve or change colors of substances. It forms a bright red complex with ferric ions. Kojic acid may be used on cut fruits to prevent oxidative browning, in seafood to preserve pink and red colors, and in cosmetics. In skin care products, kojic acid functions primarily as a skin-lightening agent. It is a potent tyrosinase inhibitor. It penetrates the upper skin layers and inhibits the production of epidermal melanin. As an example of the latter, it is used to treat skin diseases like melasma. Kojic acid also has antibacterial and antifungal properties. The cocrystals of kojic acid with quercetin were found to have two times better cytotoxic activity to human cervical cancer cells (HeLa) and human colon cancer cells (Caco-2) in comparison with quercetin itself.