Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Limonene is a naturally occurring organic compound that is classified as a terpene. It is the primary constituent of the oil extracted from citrus fruit rinds and is responsible for the distinct citrus aroma and flavor.
5 Must Know Facts For Your Next Test
Limonene is a colorless liquid with a strong, pleasant citrus aroma and flavor, often described as having a lemon or orange-like scent.
Limonene is widely used in the food, cosmetic, and cleaning industries due to its natural citrus fragrance and potential antimicrobial properties.
Limonene is biosynthesized in plants through the mevalonate pathway, which involves the condensation of two molecules of isopentenyl pyrophosphate (IPP).
In addition to its use in flavors and fragrances, limonene has been studied for its potential therapeutic properties, such as its ability to act as an anti-inflammatory, antioxidant, and chemopreventive agent.
Limonene is classified as a Generally Recognized as Safe (GRAS) compound by the U.S. Food and Drug Administration (FDA) and is approved for use as a food additive and flavoring agent.
Review Questions
Describe the biosynthesis of limonene and its relationship to the mevalonate pathway.
Limonene is biosynthesized in plants through the mevalonate pathway, which involves the condensation of two molecules of isopentenyl pyrophosphate (IPP). IPP is a five-carbon precursor that serves as the building block for the synthesis of various isoprenoid compounds, including terpenes like limonene. The mevalonate pathway is a series of enzymatic reactions that convert acetyl-CoA into IPP, which is then used to construct the hydrocarbon skeleton of limonene and other terpenes.
Explain the significance of limonene's classification as a Generally Recognized as Safe (GRAS) compound and its widespread use in the food, cosmetic, and cleaning industries.
Limonene's classification as a GRAS compound by the FDA indicates that it is considered safe for use as a food additive and flavoring agent. This recognition, along with limonene's natural origin and pleasant citrus aroma, has led to its widespread use in the food, cosmetic, and cleaning industries. Manufacturers often incorporate limonene into products such as citrus-flavored foods, fragrances, and household cleaners to take advantage of its natural properties and consumer appeal.
Evaluate the potential therapeutic properties of limonene and discuss how its chemical structure and classification as a terpene may contribute to these effects.
As a terpene, limonene's chemical structure and classification as an isoprenoid compound may contribute to its potential therapeutic properties. Studies have suggested that limonene may possess anti-inflammatory, antioxidant, and chemopreventive effects. The hydrocarbon skeleton and cyclic structure of limonene, which is characteristic of terpenes, may allow it to interact with and modulate various biological pathways and cellular processes involved in inflammation, oxidative stress, and cancer development. Further research is needed to fully elucidate the mechanisms by which limonene may exert these beneficial effects and to evaluate its potential as a therapeutic agent.
Terpenes are a large and diverse class of organic compounds produced by a variety of plants. They are the primary constituents of essential oils and contribute to the characteristic aromas and flavors of many plants.
Monoterpenes are a class of terpenes that contain two isoprene units. Limonene is a common example of a monoterpene found in citrus fruits and other plants.
Isoprenoids are a class of organic compounds that are derived from the five-carbon precursor isopentenyl pyrophosphate (IPP) and its isomer dimethylallyl pyrophosphate (DMAPP). Terpenes, including limonene, are a type of isoprenoid.