Assessment, Validation and Application to Real Samples of an RP-HPLC Method for the Determination of Guayulins A, B, C and D in Guayule Shrub

Nadia Spano,Ilenia Idda,Maria Pilo,Gavino Sanna,Ancelmo Orona-Espino,Paola Meloni,Alberto Mariani,Joanna Lachowicz,Ernesto Rivera,Valeria Nurchi

doi:10.3390/separations5020023

Nadia Spano, Ilenia Idda + Show 8 more

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https://doi.org/10.3390/separations5020023

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Abstract

Guayule (Parthenium argentatum Gray) is a shrub native to the arid regions of Mexico. In the last decades, significant attention to its cultivation has arisen because it is the raw material for the production of hypoallergenic natural rubber. Guayule biomass also contains high amounts of resin, which is not normally exploited in any way. Among other sesquiterpenic esters, guayulins (i.e., the parteniol esters of cinnamic acid, guayulin A, or of anisic acid, guayulin B) are contained in resin. In addition, minor amounts of guayulin C and guayulin D are formed by degradation/oxidation of guayulins A and B, respectively. Guayulins likely act as cinnamate and p-anisate reservoirs for the Guayule shrub; in addition, it has been postulated that they might have a key role in the chemical defense system of Guayule. Furthermore, it seems reasonable that guayulins may possess significant biological properties (e.g., antibacterial and anticancer activities), in close analogy with those shown by sesquiterpene lactones contained in many other species of Parthenum genus. As a matter of fact, guayulins A and B play an important role in the synthesis of antineoplastics used in breast cancer treatment. In this contribution we propose an original and validated RP-HPLC approach to the simultaneous quantification of guayulins A, B, C and D. The procedure of resin extraction from Guayule biomass has been optimized in terms of both extraction method and solvent. RP-HPLC separation has been accomplished by an Ascentis® C18 column under isocratic elution with a 80:20 (v:v) acetonitrile:water mixture. Validation was carried out in terms of limits of detection and quantification, linearity, precision, and trueness. Finally, the method was tested with a number of fresh and seasoned samples of spontaneous Guayule shrub from Mexico.

Highlights

Guayule (Parthenium argentatum Gray) is a perennial and low-growing shrub belonging to the Asteraceae family, native to arid regions of Mexico and the southwestern United States
Acetone and ethanol, one of the most important green polar solvent, were the pure solvents used in this phase
Quantification of resin in organic extracts was performed by means of UV-Vis spectroscopy according to literature methods [25]

Summary

Introduction

Guayule (Parthenium argentatum Gray) is a perennial and low-growing shrub belonging to the Asteraceae family, native to arid regions of Mexico and the southwestern United States. Guayule plant contains a resinous material (the so-called ‘resin’), which has to be separated from rubber in order not to compromise its physical and technological properties. Since the resin fraction is soluble in polar solvents (like acetone), whereas the rubber one can be dissolved only in non-polar solvents (like hexane), sequential or simultaneous extractions have to be made in order to separate these fractions from plant tissue and, eventually, the resin from the latex [1]. The high manufacturing costs of the process of rubber extraction from Guayule make the success of its exploitation dependent to a large extent on the possibility of using as much as possible the residual plant fractions, like resin or bagasse, as raw materials to obtain high-value coproducts [4]

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