Submitted to: Journal of Essential Oil Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 31, 2002
Publication Date: N/A
Interpretive Summary: Shrubs are increasing on arid grasslands at an alarming rate, and hypotheses explaining these increases abound. However, most will agree that this trend, which proceeds at the expense of grasses, is undesirable. Many desert shrubs are unpalatable to livestock and wildlife, and shrubs are less effective than grasses at stabilizing soil and protecting watersheds. For these reasons, a long-term goal of our research is to identify factors contributing to the success of shrubs and to devise noninvasive methods for restoring grasslands. It is known that plants interact with their surroundings by producing diverse arrays of chemicals which act to kill pathogens, deter herbivores, attract pollinators, filter sunlight, and inhibit growth of neighboring plants. The array of chemicals produced by each species is unique and may include thousands of individual compounds. By identifying the compounds present in desert shrubs, we hope to identify keys to their successful competition on rangelands. In this study, we have identified 58 volatile compounds produced by Dalea formosa, commonly known as feather dalea. Some of these compounds are known to deter herbivory in other plants and possibly serve the same purpose here. Curiously, nearly half of the oil (46%) isolated from Dalea formosa was composed of three compounds (alpha-pinene, beta-pinene, and limonene) known to be cytotoxic to human tumor cells.
Technical Abstract: Psorothamnus scoparius (broom dalea) was collected from the Jornada Experimental Range in south central New Mexico. Current year's growth was collected from 10 plants, all found within an approximate 50 m radius of the GPS coordinates N 32 deg 41.286' and W 106 deg 46.922' during June 2000. Composite samples were steam distilled and the essential oil was analyzed using GC with FID and GC/MS. Mass spectra and retention indices were used to identify 64 compounds. Retention indices and EI mass spectra are also provided for 15 unknowns. Gamma-terpinene (22.3%), p-cymene (14.0%), and alpha-pinene (9.0%) were the major constituents of the oil.