Title

Extraction and Quantification of Cardiac Glycosides from Asclepias viridis Leaves

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

Date of Award

Spring 2020

Abstract

The purpose of this research was to determine how to efficiently extract cardiac glycosides from the leaves of Asclepias viridis plants, and to analyze the concentrations of these compounds. Asclepias viridis, also known as the green-flowered milkweed plant, is native to northeast Texas and is broadly distributed from south Texas north to southeast Nebraska, east to Virginia, and south to Florida. It serves as a host plant for the larva of Danaus plexippus, also known as the monarch butterfly. The larvae spend their lives and feed on the plant and, in doing so, sequester cardiac glycosides consumed from the plant. Cardiac glycosides are a class of compounds that include cardenolides, which are found in milkweed plants as well as other groups of plants, such as foxglove and oleander. These cardenolides are a defense mechanism for the milkweed plant, as well as for the monarch larva. Cardenolides are toxic when consumed in high doses because they interfere with ATPase, a protein that regulates the flux of sodium and potassium across the cell membranes of animals. For this study, dried leaf material was ground to a fine powder and cardenolides were extracted in an ethanol solution. The crude extract was used to determine cardenolide concentration using a spectrophotometer. This technique used tetranitrobiphenyl as a colorimetric reagent that complexes with cardenolides to produce a colored compound, which was measured at 575nm using Beer' s Law to calculate concentration. It has been shown in this research that female monarchs are being selective on the plants they lay eggs on some years, but not in other years. There was no evidence of cardenolide induction through the two years studied. Finally, there was no evidence found that higher cardenolide concentration leads to mortality in larvae.

Advisor

Bukuo Ni

Subject Categories

Chemistry | Physical Sciences and Mathematics

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