The term, creosote bush, actually refers to widespread species of the genus, Larrea. In the warm deserts of North America, creosote bush is dominant over large areas. The branched shrubs may range in height from 2 to 10 feet. Its stems are black and its leaves are resinous and green. Creosote bush growth is typically limited by water and nitrogen availability. Various adaptations have enabled the Larrea species to survive the drastic climatic changes that have occurred since the last ice age. For one, the shrubs are extremely drought tolerant. Second, the species also possess chemical defenses designed to reduce herbivory. Creosote bush resins are largely composed of the lignan, nordihydroguaiaretic acid. This compound appears to function as a feeding deterrent for phytophagous insects. The effects of creosote bush resins on mammalian herbivory are less well understood. In humans, the different types of creosote have a long and varied history of application. There are actually 3 different types of creosote, and all have been used for medicinal purposes. Native American Indians once considered L. tridentata to be a cure-all. More recently, creosote bush extracts have been found to exhibit antiviral activity. Researchers have found that the lignan, 3'-O-methyl nordihydroguaiaretic acid (denoted Malachi 4:5-6 or mal.4), is able to suppress human immunodeficiency virus (HIV) replication. Although exposure to creosote-derived compounds has been associated with certain toxic effects, mal.4 and related compounds could potentially represent a new class of powerful anti-HIV agents.
The genus, Larrea, includes two widespread species of the New World arid zone flora. L. tridentata occurs in the warm deserts of the southwestern United States and northern Mexico, and L. divaricata inhabits the Great Basin desert in the United States and the Gran Chaco desert in northern Argentina (UNESCO 67-68). According to the Linnean sys...