José M. Olías

Methyl jasmonate vapor promotes β-carotene synthesis and chlorophyll degradation in Golden Delicious apple peel

Methyl jasmonate (JAMe) vapors (⩽8 ppm) for 4 h at 25°C dramatically increased Golden Delicious apple peel β-carotene synthesis by nearly threefold to 35 ng/mm2, while control fruits remained nearly constant at 11 ng/mm2 during the 10 day measurement period. Chlorophyll a and to a lesser extent chlorophyll b and lutein degradation were accelerated by JAMe treatment, but all showed some recovery after 6 days. Peel chlorophyll a∶b ratio held almost constant at 4.2–4.5 in control fruits during 10 days, while JAMe-treated apple chl a∶b ratio decreased linearly to 2.9 during 10 days.

Analysis of secreted flavonoids of Cistus ladanifer L. by high-performance liquid chromatography–particle beam mass spectrometry

Abstract The analysis of secreted flavonoids of the leaf Cistus ladanifer was carried out by high-performance liquid chromatography–mass spectrometry coupled through a particle beam interface. The mass spectra were recorded using electron impact. Apigenin, 4′-methyl-apigenin, 7-methyl-apigenin, 7,4′-dimethyl-apigenin, 3-methyl-kaempferol, 3,4-dimethyl-kaempferol, 3,7-dimethyl-kaempferol and 3,7,4′-trimethyl-kaempferol were identified in the leaf resin.

Effect of methyl jasmonate on ethylene biosynthesis and stomatal closure in olive leaves

Abstract The influence of methyl jasmonate (MeJA) on ethylene production and 1-aminocyclopropane-1-carboxylic acid (ACC) and malonyl-ACC (MACC) contents in olive leaf discs and detached leaves was investigated. In leaf discs, both ACC content and ethylene-forming enzyme (EFE) activity were clearly stimulated by 45 μM MEJA. In detached leaves MeJA treatment increased ACC content with no clear increase in ethylene production. When detached leaves were incubated with MeJA (45 μM) and ACC (1 mM), the total endogenous ACC content was significantly lower than that of leaves incubated only with ACC (1 mM). These data could be explained on the basis that MeJA caused stomatal closure, and hence reduced ACC uptake.

Purification and characterization of tomato lipoxygenase

Abstract Lipoxygenase was partially purified (26-fold) from tomato ( Lycopersicon esculentum ) fruits by ammonium sulphate precipitation and hydrophobic chromatography, and further characterized by disc gel electrophoresis, chromatofocusing and M , determination. The enzyme had a pH optimum of 6.8, and K m values for linoleic acid and linolenic acid of 1.42 and 2.60 mM, respectively. The pI was 6.3 and electrophoresis at pH 8.0 revealed a major lipoxygenase band at R f 0.14. M , determination gave a value of 97 ± 2K. Incubation of linoleic acid with partially purified enzyme gave a mixture of linoleic hydroperoxides in which the ratio of the 9- to the 13-hydroperoxide isomer was 24:1. The major product was characterized as 9-hydroperoxyoctadeca- trans -10- cis -12-dienoic acid.

8-methoxykaempferol 3-sophoroside, a yellow pigment from almond pollen

Abstract The novel flavonol 8-methoxykaempferol 3-O-(2″-β- d -glucopyranosyl-β- d -glucopyranoside) has been found as a yellow pigment in almond pollen. In addition, trace amounts of kaempferol and quercetin 3-diglucosides have been detected. These compounds have been isolated from almond bee pollen, which is a convenient source for the study of flavonoids from natural pollen. HPLC studies show no differences in the flavonoid patterns of pollen and bee pollen, and demonstrate that 8-methoxykaempferol 3-sophoroside is the main flavonoid in almond pollen, while other flower and leaf tissues are devoid of this pigment. This compound is also absent from other botanically related pollens (plum, apple, cherry, and pear).

Purification and catalytic properties of chickpea lipoxygenases

Abstract Two lipoxygenase isoenzymes, CL-1 and CL-2, were purified to apparent homogeneity from chickpea cv Pedroxillano by ammonium sulphate fractionation, gel filtration, ion exchange and hydrophobic chromatography. CL-1 and CL-2 had pH optima of 6.0 and 5.5, with apparent KM values for linoleic acid of 192 and 51μM respectively. Unlike CL-2, which produced only hydroperoxides, CL-1 simultaneously produced hydroperoxides and carbonyl compounds and exhibited high co-oxidative activity with carotene and retinol substrates. Both isoenzymes preferred linoleic acid as substrate. CL-1 was thermally more stable than CL-2, and exhibited the unusual property that its specific activity decreased with enzyme concentration.

Production of biosurfactants by Cladosporium resinae

SummaryCladosporium resinae produces extracellular biosurfactants when growing in a hydrocarbon source such as the jet fuel JP8. This production of biosurfactants was observed by the reduction of the surface tension of the aqueous phase of growing medium, and by the increase in emulsion and foaming properties. A partial purification by collapsed foam gave better physical properties by decreasing surface tension and increasing foaming power and stabilization of emulsions. Surface active substances were purified by reversed phase chromatography. Six compounds representing over 75% of fraction containing surface activity were present. This fraction gave an improvement of all surface properties.

Characterization of lupin seed lipase

Abstract Crude lipase has been extracted from ungerminated lupin seed. The lipase has an optimal activity at pH 5·0, an optimum temperature of 25°C and an activation energy of 1·32kJ mol−1, showing an induction period of 10 min. A crude extract lost more than 70% of lipase activity after 24 h. Lipase activity is stimulated by the concurrent presence of potassium (10 m m ) with calcium (1 m m ) or magnesium (1m m ) ions. The enzyme exhibits a certain specificity in releasing fatty acids from the primary rather than from the secondary position of triglycerides of lupin oil. At the primary position it is more active on saturated than on unsaturated fatty acids.

Physico-chemical properties of chickpea lipoxygenases

Abstract Purified lipoxygenase isoenzymes from chickpea ( Cicer arietinum ) cv Pedroxillano are single polypeptide chains with M r s of 96 000–97 000, determined by hydrodynamic and electrophoretic methods. Both isoenzymes difrered in pI , 4.92 for CL-1 and 4.74 for CL-2. Each isoenzyme contained one atom of iron in a divalent oxidation state. CL-1 contained 760 amino acid residues and CL-2 753 residues, with a high proportion of hydrophobic amino acids, particularly proline and leucine. Eight and seven cysteines were also present, two and three of which were as free sulphydryl residues, in CL- 1 and CL-2, respectively. Thiols, sulphur bridges and carboxyl and amine groups seemed to be essential in the maintenance of a catalytically active tertiary structure in both isoenzymes. CL-2 formed mainly 13-hydroperoxy-(9 Z , 11 E )-octadecadienoic acid from linoleic acid, while CL- 1 yielded almost equal proportions of the 9-and 13-hydroperoxides, and the 9- and 13-ketodienes.