Terpenes - What ar they and what do they do in cosmetics ?

What are terpenes?

Terpenes belong to a large group of chemical compounds. There are around 8,000 terpenes and up to 30,000 substance related. They are considered lipids and occur mainly in plants^[1].

What are terpenes chemically?

Fig. 1 The isoprene

Terpenes are all derived from isoprene. This was named after the resin resin turpentine. One can not make out a clear group of substances from the terpenes, as there are too many variations. They occur as hydrocarbons, aldehydes, ketones, glycosides, alcohols, ethers or carboxylic acids. They are found mainly in plants, mostly in their oils, resins, flowers, leaves and barks. Many of them are antimicrobial, and insect pheromones^[2].

One differentiates into the following subgroups:

- Monoterpenes: There are about 900 known pieces. They have high bioavailability and anti-carcinogenic effects. They are part of essential oils. e.g. Geraniol, citral, limonene, menthol

- Sesquiterpenes: There are more than 3000 known. They consist of three isoprene units, all derived from farnesyl pyrophosphate. They are found in vegetable oils of e.g. Hops, roses, chamomile. e.g. Humulan, farnesol, bisabolol

- Diterpenes: There are about 5000 pieces known. They each consist of two isoprene units. They are found in some plants. A representative group put the A vitamins such as retinal and retinol there.

- Sesterpene: There are about 150 known pieces. They occur in lower mushrooms, as well as sponges. They have as a basic structure the furan, and special antibacterial effects.

Fig. 3 The squalane molecule

- Triterpene: There are about 1700 pieces. They each consist of 6 Isoprene units, and are all derived from squalane. They come in e.g. Fern, birch and irises in front. Their cyclic variants have Hopan or Steran skeletons.

- Tetraterpenes: Consist of eight isoprene units, and have as subgroup all carotenoids.

- Polyterpenes: Consist of more than eight isoprene units. They are found in natural rubber, e.g. In the rubber tree, or in the latex of certain plants^[3].

What are the uses of terpenes?

Terpenes are part of many vegetable oils, and make up a large part of the essential oils. They have very unique smells and tastes, and are therefore used in perfumes and cosmetics. Most recently, they appear promising in the pharmaceutical industry. For example, they are to be used in cancer research, but they have not been thoroughly explored enough. They are also used as environmentally friendly insecticides^[4].

What do terpenes in cosmetics do and are they harmful?

Terpenes are found in natural cosmetics, but also in conventional cosmetics. They make up the majority of essential oils, which is why they are contained in many, which is offset with fragrances. They are also contained in herbal extracts and oils. Many of them have good properties for cosmetics, but some are so-called allergens. Citral, limonene, geraniol, etc. May cause skin irritation, redness and itching in sensitive people. Even with people who had no previous symptoms, allergies can train against such substances. So you should make a dermatologist in advance allergy tests in order to exclude early substances for topical application. Due to the sensitizing properties, however, caution should be taken as far as possible^[5].

Sources:

Wikipedia^[1]

Scientific book about terpenes^[2][3][4][5]