Labelling studies on sesquiterpene lactones and phytosterols of Gaillardia pulchella

Abstract

The flowering plant, Gaillardia pulchella, contains sesquiterpene lactones which act as anti-tumor agents. Biosynthetic studies were undertaken to elucidate the metabolic pathway to these compounds and to find other potential anti-tumor agents or compounds for structure-activity relationship studies. Compounds which showed incorporation of radioactivity from 2-¹⁴C-mevalonic and 2--¹⁴C-acetic acids were isolated and identified. It was found that incorporation of both 2-¹⁴C-mevalonic and 2--¹⁴C-acetic acids into the sequiterpene lactones was extremely low: less than 0.7 percent of the total plant-contained radioactivity with mevalonic acid and less than 1.5 percent with acetic acid. Incorporation into phytosterols was much higher, approximately 10 percent for both mevalonic acid and acetic acid. The results indicate that sequiterpene lactone biosynthesis is compartmentalized into structures impermeable to exogenously fed mevalonate and acetate.