Gerianiol is a clear or pale yellow, oily, rose-scented liquid. It is found in a wide variety of plants. Geraniums are high in gerianiol, as you can guess from the names. Aged tobacco also contains a lot of this compound. Honeybees produce geraniol from their glands to mark nectar bearing flowers and to find the entrance to their hives.

Structure and Properties of Geraniol

Geraniol is a phytonutrient in a class of chemicals called terpenes. Terpenes are hydrocarbons, which means they are made up of - guessed it - hydrogen and carbon. The word terpene is derived from the word turpentine. Terpenes contain isoprene units, which are a combination of 5 carbon atoms and 8 hydrogen atoms. The different types of terpenes are classified according to their number of isoprene units. Geraniol is a monoterpene, meaning it has two isoprene units in its chemical makeup.

Uses for Geraniol

Gardeners and herbalists have known for centuries that geraniums have insect repelling properties, and this is because their oil contains geraniol. Geraniums have a high enough geraniol quantity to extract it for commercial uses. It is used to make insect repellant, which is effective against all sorts of critters from mosquitoes, all types of flies, cockroaches and fire ants to fleas, gnats and ticks. Geraniol, like many terpenes, is also used in perfumes and aromatherapy products. It is also an additive used to improve the flavor of some cigarettes.

Geraniol is an antioxidant, and is being studied for its abilities to suppress tumour growth. In 1995 the Journal of Nutrition reported that geraniol suppressed the growth of hepatomas and melanomas transplanted to rats and mice. The journal Lipids, published by the American Oil Chemists' Society, published a study in February of 1997 showing that several terpenes, including geraniol, suppressed pancreatic tumour growth without affecting blood cholesterol levels. In 2001 The American Society for Pharmacology and Experimental Therapeutics published a study showing that geraniol inhibits growth in human colon cancer cells.

The Herb Companion has more details on studies done with geraniol and tumour suppression.

Aromatherapy clinics claim that inhaling geranium scent lowers or raises blood pressure a few points, and use it to control depression and mental disturbances. Herbalists use geranium as a skin therapy, in the form of a salve or massage oil, to treat eczema, burns, stretch marks, fungus, acne and inflammation. Geraniums are unusual among scented flowers because the scent is actually in the leaves, rather than the flower.

Here are a few more good sources of gerianiol.