Impact of Soil Nutrients and Environmental Factors on Podophyllotoxin Content among 28 Podophyllum Hexandrum Populations of Northwestern Himalayan Region Using Linear and Nonlinear Approaches

Podophyllotoxin is the active ingredient in the rhizome of an endangered Indian medicinal herb, Podophyllum hexandrum. Podophyllotoxin content in the P. hexandrum differs greatly in different natural habitats. The podophyllotoxin content reached more than 6.62% when soil pH value was about 4.82, soil organic carbon (C) was more than 3.23%, and nitrogen (N) content was more than 2.7% of soil dry weight. Available phosphorous (P) content of more than 0.419% and potassium (K) content of more than 1.56% resulted in low podophyllotoxin content. The linear relationship detected between podophyllotoxin and soil nutrients, environmental factors, and altitude suggested that further optimization of these factors are important in the conservation and exploitation of P. hexandrum in the northwestern Himalayan region, Himachal Pradesh, India. In this regard, like artificial neural network (ANN) and multiple linear regression (MLR), the prediction model used in this study to map the effect of these factors on podophyllotoxin yield will be helpful.