Dámaso Hornero-Méndez

Involvement of NADPH in the cyclization reaction of carotenoid biosynthesis

Cyclic carotenoids, e.g. β‐carotene, are formed by cyclization of an acyclic precursor, lycopene. The gene, crtY, which encodes lycopene β‐cyclase, has a partial sequence characteristic of a pyridine nucleotide binding domain, and NAD(P)H has been reported to be an absolute requirement for the cyclization reaction in vitro. By complementary incubations with lycopene as substrate and with (4R)‐[4‐2H]NADPH in 1H2O or with unlabelled NADPH in 2H2O in the presence of the purified enzyme, it has now been shown that the hydrogen atom introduced at C(2) in the cyclization comes from water and not from NADPH. The previously proposed mechanism involving the initiation of cyclization by H+ attack at C(2) of the folded acyclic end group of the precursor is thus confirmed. No hydrogen is transferred from NADPH, which is therefore not involved directly in the cyclization reaction, but must play an indirect role, e.g. as an allosteric activator.

Fermented Orange Juice: Source of Higher Carotenoid and Flavanone Contents

The intake of bioactive compounds and moderate alcohol decreases the risk of cardiovascular diseases. These effects could be joined in a beverage created by a controlled alcoholic fermentation of orange juice. The influence of controlled alcoholic fermentation on the bioactive compound profile of orange juice has not been previously evaluated, and this is the purpose of the present study. Total and individual flavanones and carotenoids significantly increased throughout the fermentation. The reason for this was an enhanced extraction of these compounds from the pulp. Besides, the potential bioavailability of flavanones increased due to a higher content of hesperetin-7-O-glucoside (2-fold higher at the end of the fermentation process). Ascorbic acid did not undergo a significant change, and only total phenolics decreased. Antioxidant capacity was also evaluated. TEAC and FRAP values remained constant throughout the process. However, ORAC and DPPH values significantly increased. Correlation analysis concluded that the increase in ORAC and DPPH values could be due to enhancement of flavanones.

Environmental-induced acquisition of nuptial plumage expression: a role of denaturation of feather carotenoproteins?

Several avian species show a bright carotenoid-based coloration during spring and following a period of duller coloration during the previous winter, despite carotenoids presumably being fully deposited in feathers during the autumn moult. Carotenoid-based breast feathers of male linnets (Carduelis cannabina) increased in hue (redness), saturation and brightness after exposing them to outdoor conditions from winter to spring. This represents the first experimental evidence showing that carotenoid-based plumage coloration may increase towards a colourful expression due to biotic or abiotic environmental factors acting directly on full-grown feathers when carotenoids may be fully functional. Sunlight ultraviolet (UV) irradiation was hypothesized to denature keratin and other proteins that might protect pigments from degradation by this and other environmental factors, suggesting that sunlight UV irradiation is a major factor in the colour increase from winter to spring. Feather proteins and other binding molecules, if existing in the follicles, may be linked to carotenoids since their deposition into feathers to protect colourful features of associated carotenoids during the non-breeding season when its main signalling function may be relaxed. Progress towards uncovering the significance of concealment and subsequent display of colour expression should consider the potential binding and protecting nature of feather proteins associated with carotenoids.

Carotenoid profiling in tubers of different potato (Solanum sp) cultivars: accumulation of carotenoids mediated by xanthophyll esterification.

The carotenoid profile of sixty potato cultivars (commercial, bred, old and native cultivars) has been characterised in order to provide information to be used in selective breeding programs directed to improve the nutritional value of this important staple food. Cultivars were segregated into three groups according to the major pigment in the carotenoid profile: violaxanthin (37 cultivars; especially those with higher carotenoid content), lutein (16 cultivars), and neoxanthin (7 cultivars). Other minor carotenoids were antheraxanthin, β-cryptoxanthin and β-carotene, while zeaxanthin was absent in all sample. The total carotenoid content ranged from 50.0 to 1552.0 μg/100 g dry wt, with an average value of about 435.3 μg/100 g dry wt. Sipancachi, Poluya and Chaucha native cultivars showed the highest carotenoid content (1020.0, 1478.2 and 1551.2 μg/100 g dry wt, respectively). Xanthophyll esters were present in most cultivars, mainly as diesterified forms, being observed a direct correlation between the carotenoid content and the esterified fraction, suggesting that the esterification process facilitates the accumulation of these lipophilic compounds within the plastids. Therefore, the presence of xanthophyll esters should be a phenotypic character to be included in the breeding studies, and more efforts should be dedicated to the understanding of the biochemical process leading to this structural modification of carotenoids in plants.

Involvement of copper and zinc ions in green staining of table olives of the variety gordal

The presence of metalochlorophyllic complexes of copper has been detected in table olives showing the alteration known as green staining. These compounds are absent in the healthy fruit. The possible implication of fungicidal treatment of olive trees in this alteration has been studied. No alteration was produced in table olives prepared with fruit from trees with and without fungicidal treatment and the differences found between copper levels in the fruit were not significant. The possibility that the copper involved in this alteration is of extraneous origin was, therefore, discarded. On the other hand, there were no significant differences in the levels of copper in random samples of fruits with and without green staining. Therefore, although the green-staining alteration is the result of the formation of complexes of copper with chlorophyll derivatives, it seems clear that the simple presence in the fruits of copper, by itself, does not lead to the appearance of green-staining.

Identification and Quantitative Analysis of Carotenoids and Their Esters from Sarsaparilla (Smilax aspera L.) Berries

The carotenoid composition of sarsaparilla ( Smilax aspera L.) berries has been analyzed for the first time. Lycopene was found to be the main carotenoid (242.44 μg/g fresh wt) in the pulp, followed by β-carotene (65.76 μg/g fresh wt) and β-cryptoxanthin (42.14 μg/g fresh wt; including the free and esterified forms). Other minor carotenoids were lycophyll (13.70 μg/g fresh wt), zeaxanthin (8.56 μg/g fresh wt; including the free and esterified forms), lutein (0.94 μg/g fresh wt), and antheraxanthin (0.58 μg/g fresh wt). β-Cryptoxanthin and zeaxanthin were present in free and esterified forms. β-Cryptoxanthin was mainly esterified with saturated fatty acids (capric, lauric, myristic, palmitic, and stearic), although a low amount of β-cryptoxanthin oleate was also detected. In the case of zeaxanthin, only a monoester with myristic acid (zeaxanthin monomyristate) was identified. The diverse carotenoid profile, some with provitamin A activity, together with the relatively high content, up to 375 μg/g fresh wt, makes sarsaparilla berries a potential source of carotenoids for the food, animal feed, and pharmaceutical industries.

Rapid high-performance liquid chromatography analysis of biogenic amines in fermented vegetable brines

The presence of biogenic amines in fermented vegetable products is rare, although abnormal fermentation processes may lead to the growth of microorganisms and the amino acid decarboxylase activity that can produce them. Simple methods for the determination of such amines will help considerably in their control. A methodology for the analysis of biogenic amines in fermented vegetable brines has been developed. By means of benzoyl derivatization, nine biogenic amines, namely tryptamine, β-phenylethylamine, putrescine, cadaverine, histamine, tyramine, spermidine, spermine, and agmatine could be analyzed by reverse-phase high-performance liquid chromatography (HPLC) in only 13 min. Quantification was achieved by using 1,8-diamineoctane as internal standard. The method consists basically of treating a precleaned sample with benzoyl chloride, as derivatizating reagent, in a strongly alkaline medium. The benzoylamine derivatives are extracted with diethyl ether, and after evaporation the residue is redissolved in methanol and analyzed by HPLC. By using UV-visible spectrophometric detection at both 225 and 254 nm, detection limits between 5.60 and 54.40 pg were achieved. The method appears to be applicable to a wide variety of brine samples, such as those from green table olives, cucumbers, and lupine.

Decoloration of vegetable oils and oleoresins with recovery of unaltered pigments

The present study confirms that N,N-dimethylformamide for the extraction of chloroplast pigments from vegetable tissues shows no differences from the usual acetone or methanol. Therefore, it can be applied to fats, as it allows separation of lipids and pigments by means of phase distribution between light petroleum ether and N,N-dimethylformamide. The ether phase retains the decolored fatty matter, and the pigments dissolved in N,N-dimethylformamide can be recovered totally unaltered.This method has been applied to oleoresins and oils from different products and origins. Satisfactory results have been obtained in terms of the degree of decoloration and the percentage of oil recovered. At the same time, the unaltered pigment concentrate obtained from the hypophase could be used as a color enhancer in the chemico-pharmaceutical industry.

Increase in transcript accumulation of Psy1 and e-Lcy genes in grain development is associated with differences in seed carotenoid content between durum wheat and tritordeum

Carotenoid rich diets have been associated with lower risk of certain diseases. The great importance of cereals in human diet has directed breeding programs towards carotenoid enhancement to alleviate these deficiencies in developing countries and to offer new functional foods in the developed ones. The new cereal tritordeum (×Tritordeum Ascherson et Graebener) derived from durum wheat (Triticum turgidum ssp. durum) and the wild barley Hordeum chilense, naturally presents carotenoid levels 5–8 times higher than those of durum wheat. The improvement of tritordeum properties as a new functional food requires the elucidation of biosynthetic steps for carotenoid accumulation in seeds that differ from durum wheat. In this work expression patterns of nine genes from the isoprenoid and carotenoid biosynthetic pathways were monitored during grain development in durum wheat and tritordeum. Additionally, a fine identification and quantification of pigments (chlorophylls and carotenoids) during grain development and in mature seeds has been addressed. Transcript levels of Psy1, Psy2, Zds, e-Lcy and b-Lcy were found to correlate to carotenoid content in mature grains. The specific activation of the homeologous genes Psy1, e-Lcy from H. chilense and the high lutein esterification found in tritordeum may serve to explain the differences with durum wheat in carotenoid accumulation.

The chloroplast NADPH thioredoxin reductase C, NTRC, controls non-photochemical quenching of light energy and photosynthetic electron transport in Arabidopsis.

High irradiances may lead to photooxidative stress in plants, and non-photochemical quenching (NPQ) contributes to protection against excess excitation. One of the NPQ mechanisms, qE, involves thermal dissipation of the light energy captured. Importantly, plants need to tune down qE under light-limiting conditions for efficient utilization of the available quanta. Considering the possible redox control of responses to excess light implying enzymes, such as thioredoxins, we have studied the role of the NADPH thioredoxin reductase C (NTRC). Whereas Arabidopsis thaliana plants lacking NTRC tolerate high light intensities, these plants display drastically elevated qE, have larger trans-thylakoid ΔpH and have 10-fold higher zeaxanthin levels under low and medium light intensities, leading to extremely low linear electron transport rates. To test the impact of the high qE on plant growth, we generated an ntrc-psbs double-knockout mutant, which is devoid of qE. This double mutant grows faster than the ntrc mutant and has a higher chlorophyll content. The photosystem II activity is partially restored in the ntrc-psbs mutant, and linear electron transport rates under low and medium light intensities are twice as high as compared with plants lacking ntrc alone. These data uncover a new role for NTRC in the control of photosynthetic yield.