Rutin is a polyphenol flavonoid found in many plants, for example, citrus fruits. The main reason it's used in cosmetics is its high antioxidant and free radical-scavenging ability (similar to that of superstar ascorbic acid), but also has some antibacterial nature and wound-healing properties.
There is also an in-vitro (made in Petri dishes on animal cell lines) study showing potential for rutin as a skin-whitening agent and people have even tried using it to increase the UV-blocking ability of SPF agents, but with inconsistent results. Either way, its antioxidant abilities should still help protect the skin against sun damage from the UV light that isn’t blocked by SPF agents!
Show me some proof
- Pyo, Sung Min, Martina Meinke, Cornelia M. Keck, and Rainer H. Müller. 2016. “Rutin—Increased Antioxidant Activity and Skin Penetration by Nanocrystal Technology (SmartCrystals).” Cosmetics 3 (1): 9.
- Taira, Junsei, Eito Tsuchida, Masatsugu Uehara, Natsuko Ohhama, Wakana Ohmine, and Takayuki Ogi. 2015. “The Leaf Extract of Mallotus Japonicus and Its Major Active Constituent, Rutin, Suppressed on Melanin Production in Murine B16F1 Melanoma.” Asian Pacific Journal of Tropical Biomedicine 5 (10): 819–23.
- Tran, Ngoc Quyen, Yoon Ki Joung, Eugene Lih, and Ki Dong Park. 2011. “In Situ Forming and Rutin-Releasing Chitosan Hydrogels As Injectable Dressings for Dermal Wound Healing.” Biomacromolecules 12 (8): 2872–80.
- Velasco, Maria Valéria Robles, Fernanda Daud Sarruf, Idalina Maria Nunes Salgado-Santos, Carlos Alberto Haroutiounian-Filho, Telma Mary Kaneko, and André Rolim Baby. 2008. “Broad Spectrum Bioactive Sunscreens.” International Journal of Pharmaceutics 363 (1): 50–57.
- Watt, Elmarie van der, and Johan C Pretorius. 2001. “Purification and Identification of Active Antibacterial Components in Carpobrotus Edulis L.” Journal of Ethnopharmacology 76 (1): 87–91.
- Yang, Jianxiong, Juan Guo, and Jiangfeng Yuan. 2008. “In Vitro Antioxidant Properties of Rutin.” LWT - Food Science and Technology 41 (6): 1060–66.