M. D. Fuster

Effects of α- and γ-tocopherols on the autooxidation of purified sunflower triacylglycerols

The antioxidant effects of α- and γ-tocopherols were evaluated in a model system based on the autooxidation of purified sunflower oil (p-SFO) triacylglycerols at 55°C for 7 d. Both tocopherols were found to cause more than 90% reduction in peroxide value when present at concentrations >20 ppm. α-Tocopherol was a better antioxidant than γ-tocopherol at concentrations ≤40 ppm but a worse antioxidant at concentrations >200 ppm. Neither α- nor γ-tocopherol showed a prooxidant effect at concentrations as high as 2000 ppm. The amount of tocopherols consumed during the course of oxidation was positively correlated to the initial concentration of tocopherols, and the correlation was stronger for α- than for γ-tocopherol. This correlation suggested that, besides reactions with peroxyl radicals, destruction of tocopherols may be attributed to unknown side reactions. Addition of FeSO4, as a prooxidant, caused a 12% increase in the peroxide value of p-SFO in the absence of tocopherols. When tocopherols were added together with FeSO4, some increase in peroxide value was observed for samples containing 200, 600 or 1000 ppm of α- but not γ-tocopherol. The addition of FeSO4, however, caused an increase in the amount of α- and γ-tocopherols destroyed and led to stronger positive correlations between the amount of tocopherols destroyed during oxidation and initial concentration of tocopherols. No synergistic or antagonistic interaction was observed when α- and γ-tocopherols were added together to autooxidizing p-SFO.

Citrus limon: a source of flavonoids of pharmaceutical interest

Some of the medicinal properties of lemons are due to the flavonoids they contain since they are involved in many biological activities and have many health-related functions. The levels of the principal flavanones and flavone found in different cultivars of Citrus limon, are analysed in an attempt to identify the most interesting as regards the content of such secondary compounds. The results show that the immature fruits from cultivars Lisbon and Fino-49 are ideal for obtaining the flavanone hesperidin, while the mature fruits of cultivar Fino-49 and the leaves of cultivar Eureka are the most interesting for obtaining the flavone diosmin and the flavanone eriocitrin.

Citrus cultivars with high flavonoid contents in the fruits

Abstract The flavanone contents of some lesser known citrus cultivars grown in Cuba have been determined in research searching for citrus species/cultivars with high flavanone contents. The cultivar ‘Galleta’ of the mandarin (Citrus reticulata Blanco) has a higher hesperidin content than the hybrid mandarin ‘Nova’, which is currently being used for the commercial obtainment of this flavanone. The grapefruit cultivar ‘Isaac’ had higher naringin levels than reported in the literature for any citrus species or cultivar. These two species seem potential candidates for the industrial obtainment of flavanones. With regard to neohesperidin, the ‘Afin’ and ‘Bouquet de Fleur’ varieties of Citrus aurantium L. from Spain are the best choices. A preliminary study indicated that the high flavanone contents resulted from the genetic characteristics of the cultivars, rather than from climatic effects.

Tylose formation and changes in phenolic compounds of grape roots infected with Phaeomoniella chlamydospora and Phaeoacremonium species.

The role of phenolic compounds in strengthening resistance of grapevine to young grapevine decline was analysed. The formation of tyloses has also been associated with this disease. A microscopic study showed that tyloses originated in parenchyma cells associated with the xylem and from there invaded the xylem lumen. As tyloses formed, there were changes in the cell wall, associated with the accumulation of crystalline structures. The cells surrounding the blocked xylem contained more polyphenolic compounds than the cells of intact xylem. Changes in the level and composition of polyphenolic compounds occurred in relation to the severity of infection. Tannin concentrations also increased with increasing numbers of xylem vessels containing tyloses. Root extracts added to fungal culture media inhibited mycelial growth of Phaeomoniella chlamydospora, Phaeoacremonium aleophilum and Pm. inflatipes. Inhibition was greater with extracts from roots with tyloses, and was also correlated with polyphenol content. Extracts of the leaves, stems and berries of vines treated with Brotomax, which increases the biosynthesis of phenolic compounds, inhibited mycelial growth of the fungi compared to untreated control plants.

Selection of citrus varieties highly productive for the neohesperidin dihydrochalcone precursor

Abstract The levels of the flavanones, neohesperidin and naringin, and the neohesperidin naringin ratio in immature and mature fruit of different varieties of Citrus aurantium and the Citrus paradisi Macf. × Citrus depresssa Hayata hybrid are compared, and the flavonic content is analysed for the first time. Fruits of the hybrid, which are used to obtain neohesperidin for industrial-scale transformation into the intensely sweet neohesperidin dihycrochalcone, have two advantages: (1) although the levels of neohesperidin in the hybrid are similar to those detected in the immature fruit of Citrus aurantium , the levels of naringin detected in the immature fruit of the hybrid are lower, which means that the neohesperidin naringin ratio is greater and the need for costly neohesperidin purification processes correspondingly less; (2) unlike the mature fruit of Citrus aurantium , the mature fruits of the hybrid accumulate high levels of neohesperidin with a high neohesperidin naringin ratio, so that these too can be used to obtain neohesperidin.