|Estell, Richard - Rick|
Submitted to: Journal of Essential Oil Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2002
Publication Date: 11/30/2005
Citation: Lucero, M.E., Estell, R.E., Sedillo, R. 2005. The composition of Dalea formosa oil determined by steam distillation and solid-phase microextraction. Journal of Essential Oil Research. 17:645-647.
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: Dalea formosa Torr. (feather dalea, featherplume) 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 N32o40.645' and W106o33.601' during July 2001. Composite samples of the plants were steam-distilled in triplicate, and the essential oil was analyzed using both GC-FID and GC/MS. To explore the possibility of using solid-phase microextraction (SPME) in place of steam distillation, compositions of plants collected from the same site were also examined using SPME. Mass spectra and retention indices were used to identify 58 previously described compounds. The retention index and EI mass spectra are provided for one unknown. Alpha-pinene (31.7%), camphene (8.4%), and limonene (8.1%) were the major constituents of the oil. Beta-pinene made up only 5.8% of the oil but accounted for 13.2% of the SPME chromatogram peak area. This difference in composition may be du to either sampling technique or harvesting time.