Mary E. Lucero,* Rick E. Estell and Ruth L. Sedillo

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 N32°40.645’ and W106°33.601’ during July 2001. Composite samples of the plants were steam distilled in triplicate, and the composite oil was analyzed using both GC-FID and GC/MS. The volatile composition of plants collected from the same site was also examined using solid-phase microextraction (SPME) with a 100 μm polydimethylsiloxane fi ber. 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. The most abundant constituents of the oil were α-pinene (31.7%), camphene (8.4%) and limonene (8.1%). In contrast, α-pinene (33.6%), β-pinene (13.2%) and camphene (11.1%) were the most abundant constituents of the SPME samples. This difference in composition may be due to either sampling technique or harvesting time.

Dalea formosa Torr., commonly known as feather dalea, is a woody shrub of the family Fabaceae found on rocky hillsides from southeastern Colorado to northern Mexico, and from Arizona east to Oklahoma and Texas. The plant has been described as good native browse for deer (1) and antelope (2). The Dalea genus is large, consisting of at least 250 species in the Americas (3), yet only a few of these have been examined chemically. Of those species that have been studied, phenolic compounds have been emphasized (3-6), with little attention given to the volatile fraction. We found no published essential oil compositions for any member of the Dalea genus. Our group is working to describe the volatile compounds of Chihuahuan Desert plants (7-10) and explore interactions between plant volatiles and large herbivores (11-13). In the oil compositions we have published to date, oils have been isolated using steam distillations of above-the-ground tissues or ethanol extraction of leaf-surface volatiles. Steam distillation is a tedious approach that is diffi cult to apply to large numbers of samples. This has restricted our ability, with available resources, to examine plant-to-plant and seasonal variation of oil production. In Flourensia cernua D.C., ethanol extraction of leaf surfaces provided oil profi les similar to those obtained by steam distillation (8). However, with some plant species, ethanol extracts contain many semi-volatile compounds that are diffi cult to remove from GC columns and injectors (unpublished data). Therefore, a second objective of this study was to explore the ability of solid phase microextraction (SPME) to detect a broad range of plant volatiles.