Nootkatone for Insect Repellent Protection Antioxidant Defense and Neuroprotective Support

1. Description

Nokaton is a naturally occurring sesquiterpene compound first isolated from grapefruit juice and peel oil; it is widely found in citrus fruits and Alaskan goldenseal. It appears as a white to pale yellow crystalline powder or a colorless to pale yellow liquid with a characteristic citrus and grapefruit aroma. It is soluble in dimethyl sulfoxide, dimethylformamide, and ethanol, and slightly soluble in water. It should be stored at 2–8°C in a light-protected, sealed, and dry container. The U.S. Food and Drug Administration (FDA) lists it as a food additive generally recognized as safe (GRAS).

2. Application

(1) Food and Beverage Industry: Used as a flavoring agent and flavor enhancer in beverages, frozen dairy products, baked goods, and fruit-flavored products to impart a grapefruit flavor.

(2) Fragrance and Flavor Industry: Widely used in perfumes, cosmetics, and personal care products to provide citrus-like aromatic characteristics.

(3) Pest Control Research: Used in the development of repellents and insecticides targeting pests such as mosquitoes, lice, fleas, ticks, and termites. The U.S. Environmental Protection Agency (EPA) has approved it as an active ingredient in mosquito repellents and insecticide products.

(4) Research and Development: Used as an analytical standard for quantitative analysis and pharmacological experiments; serves as a tool compound in metabolic studies, platelet function studies, and neuroprotective research.

3. Main Efficacy

(1) Repellent and insecticidal activity: It is lethal to mosquitoes, lice, and fleas, with half-maximal lethal concentrations (LC₅₀) of 0.0046%, 0.0029%, and 0.0061% w/v, respectively. Pretreatment of wood reduces the tunnel length, feeding volume, and survival rate of Formosan termites. The mosquito repellent product NootkaShield, approved by the U.S. EPA, uses nootkatone as its active ingredient.

(2) Antiplatelet aggregation effects: Inhibits collagen-, thrombin-, and arachidonic acid-induced platelet aggregation in a dose-dependent manner within the concentration range of 10–100 μM, with nearly complete inhibition at the highest concentration.

(3) Metabolic modulatory effects: It dose-dependently activates AMPKα1 and AMPKα2 in C2C12 mouse myoblasts. In mice fed a high-fat, high-sucrose diet, oral administration of 0.1–0.3% resulted in a dose-dependent reduction in body weight and blood glucose levels.

(4) Anti-inflammatory and neuroprotective effects: In a lipopolysaccharide-induced Alzheimer’s disease mouse model, a 10 mg/kg dose improved cognitive impairment, reversed neuronal degeneration and astrocyte activation, and reduced the expression of pro-inflammatory cytokines such as IL-1β, IL-6, and TNF-α in the hippocampus.

(5) Antioxidant Effects: It exhibits antioxidant activity, scavenges free radicals, and protects cells from oxidative stress damage.