Argentatin Content in Guayule Leaves (Parthenium argentatum A. Gray)

Abstract

Approximately one-third of the waste biomass from the cultivation of guayule (Parthenium argentatum A. Gray) for natural rubber production is leaf tissue; however, whether it can be valorized is not known. Guayulins and argentatins are potential high-value products that can be recovered from guayule resin during rubber/latex processing. Argentatins are highly abundant in guayule stem resin; however, unlike the guayulins, their occurrence in leaves has not been investigated. The present study determined the content of argentatins and isoargentatins A and B in the leaves of a pure guayule accession (R1040) and two hybrids (CAL-1 and AZ-2) under conditions of irrigation and non-irrigation. The resin content in leaves was ~10%, which provides a suitable starting point for economic exploitation. The highest production of argentatins occurred in plants under irrigation, with yields of 4.2 and 3.6 kg ha−1 for R1040 and AZ-2, respectively. The R1040 accession had the highest percentage of resin and the greatest total argentatin content (24.5 g kg−1 dried leaf), principally due to the abundance of argentatin A. Contrastingly, CAL-1 consistently showed the lowest argentatin content based on dried leaf weight and production (0.6 kg ha−1). The substantial abundance of argentatins in guayule leaves suggests the potential for future exploitation.

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“…For example, a study on maize plants found that optimal leaf excision from the top of the plants signi cantly improved biomass partitioning to seeds, resulting in higher seed yield [23]. Additionally, research on guayule plants suggested that the content of certain highvalue compounds in the leaves could be exploited, implying that broader leaves may not always directly correlate with higher biomass yields [24]. Furthermore, a study on beet leaves demonstrated that the recovery of bioactive compounds from the leaves could provide a sustainable solution for underutilized by-products, indicating that broader leaves do not necessarily translate to higher biomass utilization [25].…”