Cosmetic New Raw Materials Use Purpose Interpretation Series-Antioxidants

Release time:

2023-11-17 09:32

As of November 15, 2023, NMPA announced the record of new cosmetic raw materials, a total of 23 antioxidant raw materials, second only to skin protectants and moisturizers. Different from skin protectants, moisturizers, anti-wrinkle agents, etc., which take skin as the description object, and cosmetic systems, such as solvents, preservatives, etc., the concept of antioxidants does not seem to have a clear definition. In authoritative organizations, such as PCPC and SCCS, the definition takes cosmetic formula system as the description object, and in cosmetic product efficacy claims, human skin is the description object, which is quite puzzling. Here, the editor in this comprehensive authority and cosmetics industry in various documents on the definition of antioxidants, as well as the existing antioxidant evaluation methods.

Definition of Antioxidants

An antioxidant is defined in the EU COSING as "inhibiting oxygen-promoted reactions, thereby avoiding oxidation and acidification".

The American PCPC Association defines antioxidants as "ingredients used in cosmetics to prevent or delay the acid deterioration of products (or deterioration due to reaction with oxygen). Antioxidants play a vital role in maintaining the quality, integrity and safety of cosmetics. Typical cosmetic antioxidants include reducing agents and free radical scavengers."

l Anti-oxidation mechanism

From the point of view of the cosmetic formulation system, the unsaturated fatty acid esters contained in the commonly used oils and fats will be oxidized to generate low-molecular carbonyl compounds, such as aldehydes, ketones, acids, etc., when exposed to the air, resulting in a special odor, which is a process of oxidative rancidity of oils and fats. The mechanism of lipid oxidative rancidity process is generally considered to be a free radical (free radical) chain reaction, including three stages: chain initiation, chain transmission and growth, and chain termination. Antioxidants can act as hydrogen donors to scavenge free radicals generated at the chain initiation stage, thereby inhibiting or mitigating the oxidation of fats and oils.

From the perspective of human skin, free radicals are a natural product of human survival activities, and they can also produce free radicals under the influence of the external environment (smoking and drinking, ultraviolet rays, electromagnetic waves, environmental pollutants, drugs and emotional stress, etc.). Under the action of antioxidants SOD, CAT, GSH-Px, VC and VE in the body, the balance of free radicals in the body can be maintained. When ROS content exceeds the body's ability to remove, it will cause oxidative stress. Cosmetic antioxidant mainly reduces skin damage caused by oxidative stress by scavenging free radicals, reducing ROS levels, increasing antioxidant enzyme activity, and reducing lipid metabolites.

l Anti-oxidation evaluation method

Common antioxidant evaluation methods are shown in the following table:

mechanism	Method
Oxidative degradation of lipids	Peroxide value method
	iron thiocyanate method
	conjugated diene method
	thiobarbituric acid reactant method
scavenging free radicals	oxygen radical absorption capacity
	total radical absorption capacity
	crocetin bleaching method
	β-carotene bleaching
	hydroxyl radical scavenging ability
	Superoxide anion scavenging capacity
	Hydrogen peroxide scavenging capacity
	singlet oxygen scavenging capacity
	nitrogen peroxide scavenging capacity
	Clear ABTS Ability
	Clear DPPH ability
	Clear DMPD ability
reduction ability	iron ion reduction ability
	copper ion reduction ability
	cyclic voltammetry
	determination of total phenol