## 1 Introduction  
Free radicals are chemical intermediates with single or multiple unpaired electrons and are active either as an atom, molecule, or ion. Oxygen-containing radicals are substances produced by the metabolism of oxygen in the human body and contain reactive oxygen species (ROS), singlet oxygen (1O\({}_{2}\)), hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)), superoxide anion (O\({}_{2}\)\({}^{-}\)), and hydroxyl radical (OH-) [1]. Free radicals may directly cause DNA damage, mutation, and resulting cancers, as well as phosphate peroxidation of cell membranes, thus alteringthe fluid properties of cell membranes, damaging cellular integrity, or accelerating cell aging [2; 3]. Moreover, they can continuously damage cells and tissues in the body, or lead to decreased energy and organ failure, causing diseases such as vascular sclerosis, heart disease, gout, type 2 diabetes, arthritis, cataracts, and diseases of the immune system [2; 4]. Normally, levels of free radicals in the human body are in a balanced state. When the human body is invaded by bacteria, fungi, or viruses, the body's defense system prompts phagocytes to fight. Consequently, the phagocytes produce superoxide anion and hydrogen peroxide through the catalysis of related enzymes to remove bacteria or infected cells. Therefore, the human body has a certain number of free radicals as a weapon against diseases [3; 4]. However, when polyunsaturated fatty acids in the body are attacked by free radicals, oxidation occurs and more free radicals form [1; 3]. Studies have found that stress, radiation, trauma, disease, infection, or inflammation can result in accumulation of large amounts of free radicals after activation of the body's defense system, which may attack healthy cells, trigger apoptosis, or cause cellular aging [2; 3; 4; 5; 6]. Phenolic compounds in plants are natural antioxidants. These natural antioxidants found in vegetables, fruits, and daily beverages (e.g., tea and wine) are quite effective in scavenging free radicals [7; 8; 9; 10; 11; 12; 13; 14; 15; 16]. Phenolic acids are a class of compounds formed by the substitution of hydrogen atoms on benzene rings by a carboxylic acid group and at least one hydroxyl [17]. Polyphenols are phenolics with more than one hydroxyl group in their structures, while flavonoids are a phenolic subclass composed of a common diphenylpropane structure and varying degrees of hydroxylation for oxidation and substitution, which are usually present in plants in the form of glycosides [18]. A high intake of vegetables and fruits in the diet, in which plant polyphenols composed of flavonoids act as antioxidants for the body, has been shown to have preventive effects on cancer, diabetes, and cardiovascular diseases [5; 7; 9; 15; 18]. Plant polyphenols have multiple functions, not only as antioxidants, but also as reducing agents, and, in some cases, as metal chelators [17; 18], which may reduce the risk of death from heart-related diseases in elderly men. They dilate blood vessels and have anti-cancer, anti-inflammatory, antibacterial, immune stimulating, and anti-viral effects [7; 15; 17; 19; 20]. Over the years, there has been more interest in the bioactivity and biocompatibility of plant extracts with increasing popularity of cosmetic products that contain natural plant extracts. Many natural plant extracts have attracted attention for their antioxidant or whitening effects. Several studies have shown that antioxidant activities are associated with skin-whitening and skin-energizing effects [21; 22; 23; 24; 25]. _Chrysanthemum morifolium_ Ramat is a perennial herb of the family Asteraceae that is native to China. The whole plant can be used as medicine. According to the shape and size of the dried flower heads and the length of the petals, they are classified into four types: Hang Ju, Gong Ju, Chu Ju, and Bai Ju. Traditionally, only the flowers are used in folk medicine for promoting diuresis, relieving fever, and improving vision [26; 27; 28; 29]. Chrysanthemums have been brewed to make tea for thousands of years.