I. Porras

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.

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.

Pathogenicity of Alternaria alternata on fruits and leaves of ‘Fortune’ mandarin (Citrus clementina × Citrus tangerina)

Abstract Nine isolates of Alternaria causing black rot of ‘Fortune’ mandarin were obtained from a commercial orchard in the Murcia region of south-east Spain. The isolates, according to their morphological and physiological characteristics, were identified as A. alternata. Analysis of DNA sequences of the internal transcribed spacers 1 (ITS1) and 2 (ITS2) of the ribosomal DNA corroborated the morphological identification. In this work, we evaluated the pathogenicity of each of the nine isolates on fruits and leaves as well as fruit susceptibility to the pathogen at different growth stages. Studies were performed on both wounded and unwounded fruits and leaves. Disease development was faster in wounded than in unwounded organs, one and two days after inoculation, respectively. Differences in pathogenicity were observed among the A. alternata isolates, depending on the plant organ. Immature fruits were more susceptible; fruit infection tolerance increased with maturity, for both wounded and unwounded fruits. These findings could contribute to more-successful phytosanitary management of the disease.

Effect of Ethylene on Sesquiterpene Nootkatone Production during the Maturation-Senescence Stage in Grapefruit (Citrus paradisi Macf.)

In a previous work, we described how the synthesis of nootkatone, a bicyclic sesquiterpene ketone, which is an important constituent of commercial flavourings and fragances, is correlated with the development of morphological differentiation in the cells of Citrus paradisi calli (1) and the maturation-senescence process in the fruit (2),(3).