Variation in podophyllotoxin concentration in leaves and rhizomes of American mayapple (Podophyllum peltatum L.)

Podophyllotoxin is a precursor for compounds used in the synthesis of commercially available anticancer drugs and their precursors etoposide, teniposide, and etopophos. Podophyllotoxin is currently obtained from the underground plant parts (roots and rhizomes) of Himalayan mayapple (Podophyllum emodii Wall.) but is also found in several other species, including American mayapple. There is no information in the literature on podophyllotoxin concentration in the roots or rhizomes of the American mayapple, and it was not clear if podophyllotoxin concentration in underground plant parts is correlated with the concentration in aboveground plant parts. The objective of this study was to estimate podophyllotoxin concentration in the leaves and rhizomes of 28 accessions of American mayapple under natural conditions (wild) and compare this to podophyllotoxin concentrations of the same accessions in the leaves when cultivated. Podophyllotoxin concentration in the rhizomes was positively correlated to soil organic matter content and to the concentrations of soil-available P and Na. Podophyllotoxin in the leaves was negatively correlated to soil-available Mg concentrations. The concentration of podophyllotoxin in the leaves varied from undetectable amounts to 2.52%, whereas podophyllotoxin in rhizomes varied from 0.14% to 0.42%. Most of the accessions had greater than 0.45% podophyllotoxin concentration in the leaves under both wild and cultivated conditions. There was no significant correlation between the podophyllotoxin concentrations in rhizomes and leaves; nine accessions had the highest podophyllotoxin concentration in leaves under natural environment. Another nine accessions had the highest podophyllotoxin in the leaves under cultivated conditions, and an additional eight accessions had greater podophyllotoxin concentrations in roots than in leaves irrespective of the environment. The results from this study may contribute toward developing American mayapple into a new cash crop for U.S. farmers.

Research highlights▶ This is the first report on podophyllotoxin concentration in the rhizomes of the American mayapple and the first to demonstrate that the podophyllotoxin concentration in underground plant parts is not correlated with the concentration in aboveground plant parts. ▶ This and a previous study (Zheljazkov et al., 2009) demonstrated the leaves of some colonies may have undetectable amounts of podophyllotoxin. ▶ The results suggest that wild collection of American mayapple may not be feasible and support developing high-podophyllotoxin varieties for commercial production.