A. Ortuño

Antioxidant activity of phenolics extracted from Olea europaea L. leaves

The purpose of this study was to identify the main phenolic compounds present in an olive leaf extract (OL) in order to delineate the differential antioxidant activities of these compounds through the extent of their abilities to scavenge the ABTS+ radical cation and to clarify the structural elements conferring antioxidant capacity in aqueous systems. The results show that the relative abilities of the flavonoids from olive leaf to scavenge the ABTS+ radical cation are influenced by the presence of functional groups in their structure, mainly the B-ring catechol, the 3-hydroxyl group and the 2,3-double bond conjugated with the 4-oxo function. For the other phenolic compounds present in OL, their relative abilities to scavenge the ABTS+ radical cation are mainly influenced by the number and position of free hydroxyl groups in their structure. Also, both groups of compounds show synergic behaviour when mixed, as occurs in the OL.

Enhancement of phenolic compounds in olive plants (Olea europaea L.) and their influence on resistance against Phytophthora sp.

Abstract The total phenol levels in different olive organs and tissues are studied. The HPLC-MS studies point to the presence of oleuropein, catechin and tyrosol as some of the main phenolic compounds in these extracts. The effect of Brotomax treatment on phenolic compound levels in this plant and the possible role of these compounds as antifungal agents against Phytophthora sp. are also studied. An increase in the total phenol content of leaves and stems was observed 120 days after treatment with 0.3% Brotomax. The cortex was the stem tissue which showed the greatest accumulation of these secondary compounds. An in vitro study of the inhibitory effect of these compounds on fungal growth revealed that tyrosol was the most active agent, followed by catechin and oleuropein, their fungitoxic effect being greater when they acted synergically.

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.

Beneficial action of Citrus flavonoids on multiple cancer-related biological pathways.

Attempts to control cancer involve a variety of means, including the use of suppressing, blocking and transforming agents. Suppressing agents prevent the formation of new cancers from pro-carcinogens, blocking agents prevent carcinogenic compounds from reaching critical initiation sites, while transformation agents act to facilitate the metabolism of carcinogenic components into less toxic materials or to prevent their biological actions. Flavonoids can act as all three types of agent. Epidemiological and animal studies suggest that flavonoids have a protective effect against cardiovascular diseases and some types of cancer. Although flavonoids have been studied for about 50 years, the cellular mechanisms involved in their biological action are still not completely understood. In recent years, experimental studies have provided growing evidence supporting the beneficial action of flavonoids on multiple cancer-related biological pathways (carcinogen bio-activation, cell-signaling, cell cycle regulation, angiogenesis and inflammation). Within the last decade, reports on flavonoid activity have largely associated with enzyme inhibition and anti-proliferative activity. Many of these studies have pointed to a structural-functional relationship, in that the antioxidant, enzyme-inhibition or antiproliferative activities of flavonoids are dependent on particular structural motifs. Our own studies have shown that structural factors would explain the antioxidant, antiproliferative and antimetastatic properties of some citrus flavonoids. In this paper we discuss the relation between each structural factor and the anticancer activity of Citrus flavonoids.

BIOPRODUCTION OF DIOSGENIN IN CALLUS CULTURES OF TRIGONELLA FOENUM-GRAECUM L

The production of the steroidal sapogenin, diosgenin, by callus cultures of Trigonella foenum-graecum L. (fenugreek) is described. The levels of this secondary compound were examined by high performance liquid chromatography with a diode-array detector, and its identity was confirmed by mass spectrometry. The levels of diosgenin detected in leaf callus exceeded the levels detected in stem and root calli. The diosgenin levels accumulated in leaf, stem and root calli at 45 days (maximum production) represent 22, 10 and 27%, respectively, of the levels detected in the corresponding organs of the mother plant at 45 days.

Lateral diffusion of polarly transported indoleacetic acid and its role in the growth of Lupinus albus L. hypocotyls.

The transport and metabolism of indole-3-acetic acid (IAA) was studied in etiolated lupin (Lupinus albus L, cv. Multolupa) hypocotyls, following application of dual-isotope-labelled indole-3-acetic acid, [5-3H]IAA plus [1-14C]IAA, to decapitated plants. To study the radial distribution of the transported and metabolized IAA, experiments were carried out with plants in which the stele was separated from the cortex by a glass capillary. After local application of labelled IAA to the cortex, radioactivity remained immobilized in the cortex, near the application point, showing that polar transport cannot occur in the outer tissues. However, following application of IAA to the stele, radioactivity appeared in the cortex in those hypocotyl sections below the first 1 cm (in which the capillary was inserted), and the basipetal IAA movement was similar to that observed after application of IAA to the complete cut surface. In both assays, longitudinal distribution of 14C and 3H in the stele outside the first 1 cm was positively correlated with that of cortex, indicating that there was a lateral migration of IAA from the transport pathway (in the stele) to the outer tissues and that this migration depended on the amount of IAA in the stele. Both tissues (stele and cortex) exhibited intensive IAA metabolism, decarboxylation being higher in the stele than in the cortex while IAA conjugation was the opposite. Decapitation of the seedlings caused a drastic reduction of hypocotyl growth in the 24 h following decapitation, unless the hypocotyls were treated apically with IAA. Thus, exogenous IAA, polarly transported, was able to substitute the endogenous source of auxin (cotyledons plus meristem) to permit hypocotyl growth. It is proposed that IAA escapes from the transporting cells (in the stele) to the outer tissues in order to reach the growth-responsive cells. The IAA metabolism in the outer tissues could generate the IAA gradient necessary for the maintenance of its lateral flow, and consequently the auxin-induced cell elongation.

Distribution and changes of diosgenin during development of Trigonella foenum-graecum plants. Modulation by benzylaminopurine

The distribution and evolution of diosgenin levels in the different organs of Trigonella foenum-graecum were investigated. The results revealed that the maximum levels of this secondary compound are reached in the young leaves (20mg g−1 dry weight). A considerable increase in the levels of this sapogenin was observed after treatment of seeds with benzylaminopurine. These results open up new perspectives for the possible development of plants with high concentrations of this compound.

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.

Bioproduction of neohesperidin and naringin in callus cultures of Citrus aurantium

The accumulation of both neohesperidin and naringin as major flavonoids in callus cultures of bitter orange (Citrus aurantium) was demonstrated using high performance liquid chromatography with a diode-array detector. The identity of both compounds was confirmed by their corresponding nuclear magnetic resonance spectra. The levels of neohesperidin are higher than those of naringin in callus culture, as they are in immature fruit, and high concentrations of both are found in young tissues such as immature fruits and the outer zone of calli.

Accumulation of the sesquiterpenes nootkatone and valencene by callus cultures of Citrus paradisi, Citrus limonia and Citrus aurantium

The production of the sesquiterpenes nootkatone and valencene by callus cultures of Citrus species is described. The levels of these compounds were examined by gas chromatography-mass spectrometry and their yields were compared with the amounts found in mature fruits. A simultaneous increase and decrease in the levels of nootkatone and valencene, respectively, were observed with the aging of callus cultures of Citrus paradisi. These results suggest that valencene might be a possible precursor of nootkatone in this species. The high level of nootkatone detected in 9-month-old callus cultures of Citrus paradisi might be associated with the corresponding cell morphological changes observed.