Bachelor of Science, Ashland University, 2019, Chemistry/Geology/Physics
Syrian rue (Peganum harmala), a desert plant native to the Middle East and southern Asia,
has a long history of use in rituals and folk medicine. It was introduced into the United States in the
1920's and has become an invasive plant thriving in deserts of the southwest. Syrian rue produces
six harmala alkaloids that have the potential to inhibit the growth of neighboring plants and
negatively impact organisms living in soil near its roots. In order to better understand the toxic
properties of these compounds toward other plants, the alkaloids released by Syrian rue in soil were
measured using silicone tube microextraction, a technique developed in our laboratory.
Silicone sequesters and concentrates lipophilic organic compounds, such as the harmala
alkaloids. This method also allows for repeated sampling of the soil without disturbance. The
compounds are extracted from the silicone and the concentration of each compound is measured
using high performance liquid chromatography (HPLC). Harmine and harmaline can be detected by
fluorescence detection down to 10 and 1 ng/mL, respectively. The spatial and temporal profiles of
the dynamic release of harmala alkaloids in the rhizosphere were measured using various planting
methods (pots of unique design) and variations of silicone probe designs. Silicone sheet probes show
the spatial profile of harmine ranging from 11 ng to 46 ng released in soil.
The toxic effect of the alkaloids to three dicot species (Amaranthus hypochondriacus,
Rudbeckia hirta, and Lactuca sativa) was examined. Germination and growth studies in the
presence of harmine and harmaline have shown that harmaline is more inhibitory to the plants than
harmine. Amaranth root growth was decreased by 41% for 5 μg/mL harmaline and was not affected
for 5 μg/mL harmine. Changes in amaranth root growth were seen at higher concentrations of
harmine: root growth decreased by 53% at 100 μg/mL harmine. Similar results were seen in the
other spec (open full item for complete abstract)
Committee: Brian Mohney Ph.D. (Advisor); Jeffrey Weidenhamer Ph.D. (Other)
Subjects: Agricultural Chemicals; Analytical Chemistry; Chemistry; Soil Sciences