Plant hormones, and especially auxins, are low molecular weight compounds highly involved in the control of plant growth and development. Auxins are also broadly used in horticulture, as part of vegetative plant propagation protocols, allowing the cloning of genotypes of interest. Over the years, large efforts have been put in the development of more sensitive and precise methods of analysis and quantification of plant hormone levels in plant tissues. Although analytical techniques have evolved, and new methods have been implemented, sample preparation is still the limiting step of auxin analysis. In this review, the current methods of auxin analysis are discussed. Sample preparation procedures, including extraction, purification and derivatization, are reviewed and compared. The different analytical techniques, ranging from chromatographic and mass spectrometry methods to immunoassays and electrokinetic methods, as well as other types of detection are also discussed. Considering that auxin analysis mirrors the evolution in analytical chemistry, the number of publications describing new and/or improved methods is always increasing and we considered appropriate to update the available information. For that reason, this article aims to review the current advances in auxin analysis, and thus only reports from the past 15 years will be covered.

Olive (Olea europaea) is one of the most important fruit species in the Mediterranean basin, where 95% of the world's olive orchards are planted, and it has become an economically valuable crop worldwide, due to an increasing interest in olive oil for human consumption. New olive orchards are being planted outside the Mediterranean, calling for an effort to identify the genotypes best adapted to the new conditions. However, some olive cultivars remain difficult to propagate, which significantly reduces the capacity to use the full genetic diversity of the species. Improving rooting ability in cuttings from recalcitrant olive cultivars has become a critical topic, which implies fundamental research on the anatomy, physiology, biochemistry and genetics of the adventitious root formation process. Besides, the existence of different rooting behaviors among olive cultivars also makes the species a candidate model plant for these studies. Olive propagation techniques evolved through time from field-or nursery-planted hardwood cuttings, to semi-hardwood cuttings in greenhouses under mist, and, more recently, to in vitro culture techniques. Nevertheless, research about adventitious root formation carried on each propagation method was mostly based on trial and error approaches. Researchers have mainly investigated different factors involved in the process of adventitious rooting by testing their effect in the rooting capacity of different cultivars, leading to a high dispersion and fragmentation of the available information. The goal of this review is to present the most relevant results achieved on adventitious root formation in olive cuttings, aiming to provide an integrated perspective of the current knowledge.

The esterification reaction of geraniol with acetic acid catalyzed by Novozym was studied in supercritical ethane (sc-ethane) and in supercritical carbon dioxide (sc-CO(2)). Water activity (a(W)) had a very strong effect on enzyme activity, with reaction rates increasing up to a(W) = 0.25 and then decreasing for higher a(W). Salt hydrate pairs could not prevent changes in a(W) during the course of reaction but were able to control a(W) to some extent and had a beneficial effect on both initial rates of esterification and conversion in sc-ethane. The enzyme was more active in sc-ethane than in sc-CO(2), confirming the deleterious effect of the latter already observed with some enzymes. Temperatures between 40 and 60 degrees C did not have a strong effect on initial rates of esterification, although reaction progress declined considerably in that temperature range. For the mixture of 50 mM acetic acid plus 200 mM geraniol, 100% conversion was achieved at a reaction time of 10 h at 40 degrees C, 100 bar, an a(W) of incubation of 0.25, and a Novozym concentration of 0.55 mg cm(-)(3) in sc-ethane. Conversion was below 50% in sc-CO(2) at otherwise identical conditions. With an equimolar mixture of the two substrates (100 mM), 98% conversion was reached at 10 h of reaction in sc-ethane (73% conversion in sc-CO(2)).

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The acylation of the model substrate (R,S)-2-octanol with succinic anhydride catalysed by immobilised Candida antarctica lipase B was studied in two water-miscible organic solvents, two water-immiscible ones, nine 1-alkyl-3-methylimidazolium ionic liquids (RTILs) and two quaternary ammonium RTILs. From previous reports, the reaction was expected to yield an acidic half ester (hemiester). However, it was found that the diester was also produced, in many cases at an even higher yield. The major reaction products were the (R)-hemiester and the (R,R)-diester. In some of the solvents, the amount of hemiester formed increased and then remained constant, whereas in others the amount of hemiester first peaked and then decayed. This behaviour could be explained by the coupling of two reaction pathways: the hydrolysis of the hemiester, and the esterification of the hemiester. The solubility limit of succinic acid, produced in the former pathway, was found to be a discriminating parameter, the precipitation of the acid acting as a driving force for the consumption of the hemiester formed. The impact of the choice of solvent on the outcome of the acylation with succinic anhydride was confirmed by conducting the reaction on a preparative scale: in acetonitrile, the reaction produced 32% (w/w) of (R)-hemiester and 68% (w/w) of (R,R)-diester, whereas in tetrahydrofuran 85% (w/w) of (R)-hemiester and 15% (w/w) of (R,R)-diester were obtained.

We studied the reaction between vinyl butyrate and 2-phenyl-1-propanol in acetonitrile catalyzed by Fusarium solani pisi cutinase immobilized on zeolites NaA and NaY and on Accurel PA-6. The choice of 2-phenyl-1-propanol was based on modeling studies that suggested moderate cutinase enantioselectivity towards this substrate. With all the supports, initial rates of transesterification were higher at a water activity (a(w)) of 0.2 than at a(w) = 0.7, and the reverse was true for initial rates of hydrolysis. By providing acid-base control in the medium through the use of solid-state buffers that control the parameter pH-pNa, which we monitored using an organo-soluble chromoionophoric indicator, we were able, in some cases, to completely eliminate dissolved butyric acid. However, none of the buffers used were able to improve the rates of transesterification relative to the blanks (no added buffer) when the enzyme was immobilized at an optimum pH of 8.5. When the enzyme was immobilized at pH 5 and exhibited only marginal activity, however, even a relatively acidic buffer with a pK(a) of 4.3 was able to restore catalytic activity to about 20% of that displayed for a pH of immobilization of 8.5, at otherwise identical conditions. As a(w) was increased from 0.2 to 0.7, rates of transesterification first increased slightly and then decreased. Rates of hydrolysis showed a steady increase in that a(w) range, and so did total initial reaction rates. The presence or absence of the buffers did not impact on the competition between transesterification and hydrolysis, regardless of whether the butyric acid formed remained as such in the reaction medium or was eliminated from the microenvironment of the enzyme through conversion into an insoluble salt. Cutinase enantioselectivity towards 2-phenyl-1-propanol was indeed low and was not affected by differences in immobilization support, enzyme protonation state, or a(w).

This work describes the development of a new selective photocontrollable molecularly imprinted-based sorbent for the selective enrichment/pre-concentration of dimethoate from spiked olive oil samples. To achieve this goal an improved molecularly imprinted strategy relying on the embedding of a functional monomer containing an azobenzene chromophore as light-responsive element, on the crosslinked tridimensional molecular imprinted network, has been assessed. To address the mechanisms underlying template recognition and uptake/release of the analyte from the functional imprinted material, computational studies using a quantum chemical approach, have been explored. This new functional sorbent provides a straightforward controllable uptake/release of the target template using light as the stimuli tool, which is highly advantageous due to light manipulation characteristics, such as superior clean, precision and remote controllable properties. In general, this work will contribute to the implementation of a photoswitchable analytical methodology that proves to be suitable for the selective isolation and further quantification of dimethoate from olive oil matrices at levels similar to the maximum residues limits imposed by the legislation. The limits of detection, calculated based on 3σ, was 1.6 mgL and the limit of quantification, based on 10σ, was 5.2 mgL. The implemented sample preparation shows high reproducibility and recoveries (93.3 ± 0.4%).