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Biochemical Characterization and Fuel Properties of Endemic Taurus Flowering Ash (Fraxinus ornus subsp. cilicica) Bark from Turkey
Publication . Sen, Ali Umut; Simões, Rita; Yüceda˘, Cengiz; Miranda, Isabel; Fernandes, Ângela; Pereira, Helena
Taurus flowering ash (Fraxinus ornus subsp. cilicica) is an endemic tree species in Turkey.
The bark of the species was characterized for summative chemical composition, the monomeric
composition of polysaccharides, phenolic content, in vitro and ex vivo antioxidant properties of
hydrophilic extracts, the composition of lipophilic extractives and suberin, and thermal degradation.
The bark has an elevated ash content (17%), primarily composed of calcium, and a noteworthy
extractive content (38.9%), predominantly of hydrophilic compounds. The antioxidant activity of the
bark extracts is moderate, with an IC50 value of 40 g/mL and an EC50 value of 230 g/mL by DPPH
and TBARS methods. The lipophilic extractives principally contain fatty acids and diterpenoids. The
suberin content is low (1%) and composed primarily of !-hydroxy acids with 9,10,18 trihydroxyoctadecanoic
acid as the major suberin monomer. The lignin content is low (9.8%), and polysaccharides
represent 33%. The ignition temperature of the bark is 190 C, the burnout temperature is 653 C, and
the activation energy in combustion is 29 kJ mol1. A biorefinery concept was developed considering
the bark’s chemical and thermal characteristics to convert approximately 90% of the bark mass into
valuable chemicals, extracts, functional materials, and additives.
Cuticular Waxes and Cutin in Terminalia catappa Leaves from the Equatorial São Tomé and Príncipe Islands
Publication . Pereira, Helena; Simões, Rita; Miranda, Isabel
This study presents for the first time an analysis of the content and chemical composition
of the cuticular waxes and cutin in the leaves of the widespread and important tropical species
Terminalia catappa. The leaves were collected in the equatorial Atlantic islands of São Tomé and
Príncipe, in the Gulf of Guinea. The epicuticular and intracuticular waxes were determined via
dichloromethane extraction and their chemical composition via GC-MS analysis, and the content and
monomeric composition of cutin were determined after depolymerization via methanolysis. The
leaves contained an epidermal cuticular coverage of 52.8 g cm2 of the cuticular waxes (1.4% of
mass) and 63.3 g cm2 (1.5% of mass) of cutin. Cuticular waxes include mainly n-alkanols and fatty
acids, with a substantial proportion of terpenes in the more easily solubilized fraction, and sterols
in the more embedded waxes. Cutin is mostly constituted by C16 fatty acids and dihydroxyacids,
also including aromatic monomers, suggesting a largely linear macromolecular arrangement. The
high proportion of triacontanol, a-amyrin, b-amyrin, germanicol, and lupeol in the easily solubilized
cuticular fraction may explain the bioactive properties attributed to the T. catappa leaves via the
popular medicine, which allows us to consider them as a potential source for the extraction of
these compounds.
Variation in leaf cutin content and chemical composition along one annual cycle in the Mediterranean Cork Oak (Quercus suber L.)
Publication . Simões, Rita; Sousa, Isabel; Pereira, Helena
Plant leaves have one important protection barrier made up by a cuticle that covers
their external surface and builds up a continuous extracellular, mostly hydrophobic, membrane
on the epidermis that provides protection from biotic or abiotic stresses, namely
from climatic harsh conditions, e.g., by limiting water loss and in heat insulation [1,2]. The
cuticle includes a polymeric cutin matrix and cuticular waxes, linked to the epidermal
cell wall by polysaccharides, also considered part of the cuticle as a cutin–polysaccharide
matrix. Cutin is a polyester formed predominantly by cross-linking through ester bonds
of C16 and C18 hydroxy fatty acids and glycerol, while cuticular waxes comprise very
long-chain fatty acids and derivatives, alcohols, and alkanes as well as terpenes, sterols,
and aromatics, and are soluble in non-polar solvents [3–6]. Cuticular waxes are located
in the cuticle within the cutin matrix as an intracuticular layer, and on the outer surface
of the cutin as an epicuticular layer [3]. Some cuticles also contain a resistant aliphatic
polymer that is not depolymerized by ester-bond hydrolysis, the cutan, that has only a
small proportion of aromatic moieties [7,8].
Influence of environmental conditions on the chemical composition of the cuticle of Quercus suber L. leaf
Publication . Simões, Rita Fabiana Silva; Pereira, Helena Margarida Nunes; Miranda, Isabel Maria Silva Sanches de; Gominho, Jorge
suber is a species well adapted to the environmental and climatic conditions prevailing in the Mediterranean area, with sclerophylly leaves covered by the cuticle that acts as a protective barrier to the environment. The composition of the cuticle regarding cutin and cuticular waxes can be decisive for the species performance, namely its ability to adapt to environmental conditions. This study aims to deepen the knowledge of the characteristics of Q. suber leaves, mainly regarding the quantity and chemical composition of cuticular waxes and cutin, using samples from cork oaks growing in the same location in Portugal but with different seed geographical origins. The seasonal variation of cuticular waxes and cutin throughout the leaf life cycle was studied and the experimental methodology to extract and study cutin and cuticular waxes was analysed.
Cork oak leaves after full expansion in summer have on average an area of 4.6-6.8 cm2 with a specific leaf area (SLA) of 55.6-67.8 cm2 g-1, a substantial cuticular wax coverage of 189.4 μg cm-2, composed predominantly of triterpenes and aliphatic compounds, and a cutin coverage of 518 μg cm-2, essentially composed of long-chain aliphatic ω-hydroxy fatty acids and fatty acids. No between provenances differences were found in cuticular wax and cutin content and composition.
The cork oak leaf cuticle has seasonal dynamics. The cuticular wax coverage increased from the newly expanded leaves to a maximum in the fully expanded leaves (115.7 μg cm-2, in spring; 235.6 μg cm-2, after summer). The cutin composition varied along the leaf development cycle with a significant decrease of aromatics (e.g. 24.2% in May and 8.5% in March) and an increase in -hydroxyacids (45.8% in May, 50.8% in December).
The extent and selectivity of the cuticular wax solubilization depended on the solvent and the extraction duration and solvents with low polarity such as n-hexane or dichloromethane are the most suitable for cuticular lipids extraction. Cutin depolymerization by methanolysis required 3% NaOMe catalyst concentration for complete ester bond cleavage and monomer solubilization.
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Fundação para a Ciência e a Tecnologia
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Funding Award Number
PD/BD/128259/2016