M.I. Fortea

ORAC-fluorescein assay to determine the oxygen radical absorbance capacity of resveratrol complexed in cyclodextrins.

The effect of the complexation of resveratrol with hydroxypropyl-beta-cyclodextrins (HP-beta-CDs) on the antioxidant capacity of the polyphenol is studied for the first time by means of the oxygen radical absorbance capacity (ORAC) method, using fluorescein (FL) as the fluorescent probe. The method is validated through its linearity, precision, and accuracy for measuring the ORAC of resveratrol in the absence or presence of cyclodextrins (CDs). The complexation of resveratrol in CDs increased the net area under the FL decay curve (net AUC) of resveratrol up to its saturation level, at which the polyphenol showed almost double the antioxidant activity it shows in the absence of CDs. The complexation constant ( K c) between resveratrol and HP-beta-CDs was calculated by linear regression of the phase solubility diagram ( K c = 18048 M (-1)). The antioxidant activity of resveratrol was dependent on the complexed resveratrol because CDs acts as a controlled dosage reservoir that protects resveratrol against rapid oxidation by free radicals. In this way, its antioxidant activity is prolonged and only reaches its maximum when all the resveratrol is complexed.

Kaempferol complexation in cyclodextrins at basic pH.

The complexation of kaempferol with cyclodextrins (CDs) (beta-, G(2)-beta-, and HP-beta-CDs) in basic medium was studied, and the complexation constants (K(c)) were calculated by using enzymatic, solubility, and fluorometric methods. This is the first time that a decrease in fluorescence has been observed as result of the analyte complexation by CDs. The highest K(c) value for kaempferol complexation was obtained for HP-beta-CDs. To establish the validity of the fluorometric method for determining the K(c) between kaempferol and CDs, the same parameters were also determined by enzymatic and solubility methods. The enzymatic method was carried out by using horseradish peroxidase as oxidative enzyme, and the K(c) values obtained were similar to those obtained by using the solubility method. However, the fluorometric method underestimated the K(c) value by about 1.2-fold with respect to the other methods used. In all cases HP-beta-CDs showed the highest K(c) value, indicating that they are more efficient in the formation of inclusion complexes with kaempferol.

Preparation and characterization of the inclusion complex of chlorpyrifos in cyclodextrins to improve insecticide formulations.

The chemical control of crops by organophosphate insecticide treatment is usually limited because the insecticides do not maintain their efficiency for long periods for several reasons, including environmental conditions or rapid degradation of the active ingredient. Chlorpyrifos is an organophosphate insecticide used worldwide to control a variety of soil insects and arthropods in a wide range of crops. It is easily soluble in organic solvents but shows poor water solubility. The inclusion of chrorpyrifos in cyclodextrins (CDs) improves its water solubility, bioavailability, and insecticidal activity and helps prevent overdosing, leading to more cost-effective and more environmentally friendly agricultural practices. Solubility studies of chlorpyrifos in the presence of different types of CDs show G2-beta-CDs to be the most effective CDs in the complexation process, giving 1:2 complexes, with complexation constant (Kc) values of 12.34 +/- 3.1 M(-1) for K1 and 3895 +/- 183 M(-1) for K2. These complexation constant values were corroborated by applying a fluorimetric method.

Kinetic characterisation and thermal inactivation study of red alga (Mastocarpus stellatus) peroxidase

Peroxidase (POD) was extracted from red alga (Mastocarpus stellatus) using Triton X-114 and characterised by UV-spectrophotometry. Optimum activity using 2,2´-azinobis(3-ethylbenzothiazolinesulphonic acid) (ABTS) as the H-donor was obtained at pH 5.0. In the presence of the anionic detergent, sodium dodecyl sulphate (SDS), however, POD was inactivated at all the pH values studied and totally inactivated at 1mM SDS. When the enzyme was kinetically characterised, the KM and Vm values for ABTS were found to be 13mM and 40μM/min, respectively. In addition, when the H2O2 concentration was increased, at a fixed concentration of ABTS, the activity was inhibited at the highest H2O2 concentrations. In a study of the effect of several reducing agents, l-cysteine was found to be the most active. A thermal inactivation study showed a first-order inactivation kinetic, and the Arrhenius plot yielded a straight line with a slope equivalent to an activation energy of 121.6kJ/mol. Significant inactivation occurred at temperatures of>35°C, with>90% of the relative activity being lost after only 5min of incubation at 48.4°C.

YIELD AND FRUIT QUALITY RESPONSE OF SWEET PEPPER GENOTYPES GROWN UNDER SOILLESS CULTIVATION

Total yield, physical, and phytochemical characterization of three yellow and five red-colored sweet pepper genotypes were analyzed under fully controlled environmental and irrigation conditions under soilless culture. Results showed both greater fruit firmness and pericarp thickness in the red-colored genotypes than in the yellow ones. However, no significant differences between these two colors were found for total yield, shape index and dry matter percentage. Additionally, peroxidase activity, total protein and total phenolic compounds were not modified according with the color of the genotype. With respect to the genotypes studied, ‘Cierva’, ‘A67’, ‘Traviatta’, ‘Cabezo’ and ‘Limona’ showed the highest yields in the “extra” fruit category whilst ‘Disco’ and ‘Zar’ showed the lowest. Additionally, ‘Cierva’ and ‘Cabezo’ showed higher protein concentration and peroxidase activity than any other genotype.