Proceedings of the 7th World Congress on Mechanical, Chemical, and Material Engineering (MCM'21)
Prague, Czech Republic Virtual Conference – August, 2021
Paper No. ICCPE 112
DOI: 10.11159/iccpe21.112

Silicon in Agave Angustifolia Haw Leaves
Margarita Mondragón1, Luis E. Elizalde2, Victor Rejón3
1
Instituto Politécnico Nacional, CIIDIR-Oaxaca
C. Hornos 1003, 71230 Santa Cruz Xoxocotlán, Oax., MX
mmondragon@ipn.mx
2
Centro de Investigación en Química Aplicada, CIQA
Enrique Reyna H. 140, 25294 Saltillo, Coah., MX
luis.elizalde@ciqa.edu.mx3CINVESTAV-LANNBIO
Km. 6 Carr. Mérida - Progreso, 97205 Mérida, Yuc., MXv.rejon@gmail.com

Extended Abstract

The enormous agricultural waste generated from Agave species used for the production of mezcal in the southern
Mexican state of Oaxaca, has intensified interest in finding ways to use the leaves and bagasse of these plants as sources ofraw materials for other applications [1]. The objective of this work was to determine the presence of silicon in leaves ofadult-Agave angustifolia Haw plants. Plants take up silicon from soil in the form of monomeric orthosilicic acid, which ispolymerized and precipitated as distinct silica (SiO2) bodies (phytoliths), or within certain cells [2]. Silica-based
nanomaterials have grown in importance for catalysis, biosensing and biomedical applications [3].
Middle part of leaves of adult-Agave angustifolia plants from two different regions in Oaxaca, were cut into small cubesand fixed in a solution of formalin, glacial acetic acid, ethanol (95%) and deionized water (10:5:50: 35) for 48 h. Then,
washed with deionized water and dehydrated in an ethanol series. Thin slices cut out from the cubes were observed byscanning electron microscopy with energy dispersive X-ray spectroscopy (SEM with EDX). Dehydrated samples weregrinded and vibrational spectroscopy measurements were performed at room temperature by Fourier transmission infrared(FT-IR) spectroscopy. Thin slices of non-dehydrated samples were sectioned using a razor blade and stained with safranine
for light microscopy observations.
The presence of elements-silicious and oxygen was initially confirmed in Agave leaves by sharp and strong peaks in theEDX spectra of some small areas (~ 2-5 µm). However, the EDX spectra of wider areas (~ 50 µm) in the same region showedvery small signals or none of Si, indicating the specificity of the Si location. SEM images not only revealed the formationof irregular-shaped silica particles with an average width of ~ 5 µm, but also isolated zones with Si having no capability toproduce Si particles. Although phytoliths in different Agave species (e.g., A. americana, A. tequilana, and A. atrovirens)
have been reported as composed of calcium oxalate, the possibility of phytoliths composed of amorphous silica (SiO2.nH2O)
in Agave has not been reported [4]. Conversely, photomicrographs showed prismatic structures at the junction between
parenchyma cells in Agave leaf tissue, assigned to oxalate crystals according to other authors [5]. However, our SEM images
were helpful in also observing oxalates crystals near the cuticle and guard cells of Agave leaves. The presence of the small
silica particles could not be detected by the optical microscopy technique.
FTIR spectra showed typical bands assigned to cellulose, lignin, and oxalates. In addition, FTIR spectra also showed asignal at 1050 cm-1 in the rather broad peak at ca. 1190-865 cm-1 which denoted the Si-O-Si antisymmetric stretching mode
(TO3 mode) in the Agave leaves. The shoulder toward higher frequency side, that generally accompanied the TO3 mode wasalso present (~1150 cm-1). The inflection point located at ~804 cm-1 indicated the bending vibrations of (SiO2) groups [6].
Therefore, the availability of Si in the leaves of Agave Angustifolia Haw was here confirmed by EDX and FTIR analysis.

ICCPE 112-1

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