Agronomic practices impact argentatin content in guayule (Parthenium argentatum A. Gray)

There is increasing interest in the development and exploitation of argentatin compounds from guayule (Parthenium argentatum A. Gray), which are known to have several beneficial effects on human health. However, limited information is available about the best experimental approaches for the analysis of argentations and the potential influence of agronomic practices on their yield. The aim of the present study was to develop an accurate, robust and simple analytical method to analyze argentatin A and B and isoargentatin A and B in one pure accession of guayule (R1040) and two hybrids (AZ-2 and CAL-1). Plants were grown under different conditions of irrigation and fertilization and were harvested at three different dates. Guayule resin was analyzed by liquid chromatography combined with a reflection index detector or a diode-array detector. In factor analysis, Harvest had the greatest significant effect on argentatin content, which was highest between winter and spring. Fertilization had a negative influence on argentatin accumulation in the AZ-2 hybrid, the accession with the highest content (up to 22.4 g kg−1 stem dry weight), representing up to 19.1% of the total composition of guayule resin. Contrastingly, irrigation and no fertilization had the greatest impact in the CAL-1 and R-1040 accessions. Of the three accessions studied, the combination fertilization + irrigation resulted in the poorest total content. Generally, argentatin production was lower in CAL-1 than in AZ-2 and R-1040, although a higher production of argentatin B versus argentatin A was characteristic of this accession.