Supplementary Far-Red and Blue Lights Influence the Biomass and Phytochemical Profiles of Two Lettuce Cultivars in Plant Factory.

Three different LED spectra (W: White light; WFR: W + far-red light; WB: W + blue light) with similar photosynthetic photon flux density (PPFD) were designed to explore the effects of supplementary far-red and blue lights on leaf color, biomass and phytochemicals of two cultivars of red-leaf lettuce ("Yanzhi" and "Red Butter") in an artificial lighting plant factory. Lettuce plants under WB had redder leaf color and significantly higher contents of pigments, such as chlorophyll a, chlorophyll b, chlorophyll (a + b) and anthocyanins. The accumulation of health-promoting compounds, such as vitamin C, vitamin A, total phenolic compounds, total flavonoids and anthocyanins in the two lettuce cultivars were obviously enhanced by WB. Lettuce under WFR showed remarkable increase in fresh weight and dry weight; meanwhile, significant decreases of pigments, total phenolic compounds, total flavonoids and vitamin C were found. Thus, in the plant factory system, the application of WB can improve the coloration and quality of red leaf lettuce while WFR was encouraged for the purpose of elevating the yield of lettuce.

Enrichment of provitamin A content in durum wheat grain by suppressing ß-carotene hydroxylase 1 genes with a TILLING approach.

KEY MESSAGE: The suppression of the HYD-1 gene by a TILLING approach increases the amount of ß-carotene in durum wheat kernel. Vitamin A deficiency is a major public health problem that affects numerous countries in the world. As humans are not able to synthesize vitamin A, it must be daily assimilated along with other micro- and macronutrients through the diet. Durum wheat is an important crop for Mediterranean countries and provides a discrete amount of nutrients, such as carbohydrates and proteins, but it is deficient in some essential micronutrients, including provitamin A. In the present work, a targeting induced local lesions in genomes strategy has been undertaken to obtain durum wheat genotypes biofortified in provitamin A. In detail, we focused on the suppression of the ß-carotene hydroxylase 1 (HYD1) genes, encoding enzymes involved in the redirection of ß-carotene toward the synthesis of the downstream xanthophylls (neoxanthin, violaxanthin and zeaxanthin). Expression analysis of genes involved in carotenoid biosynthesis revealed a reduction of the abundance of HYD1 transcripts greater than 50% in mutant grain compared to the control. The biochemical profiling of carotenoid in the wheat mutant genotypes highlighted a significant increase of more than 70% of ß-carotene compared to the wild-type sibling lines, with no change in lutein, α-carotene and zeaxanthin content. This study sheds new light on the molecular mechanism governing carotenoid biosynthesis in durum wheat and provides new genotypes that represent a good genetic resource for future breeding programs focused on the provitamin A biofortification through non-transgenic approaches.

Carotenoids and fatty liver disease: Current knowledge and research gaps.

Carotenoids form an important part of the human diet, consumption of which has been associated with many health benefits. With the growing global burden of liver disease, increasing attention has been paid on the possible beneficial role that carotenoids may play in the liver. This review focuses on carotenoid actions in non-alcoholic fatty liver disease (NAFLD), and alcoholic liver disease (ALD). Indeed, many human studies have suggested an association between decreased circulating levels of carotenoids and increased incidence of NAFLD and ALD. The literature describing supplementation of individual carotenoids in rodent models of NAFLD and ALD is reviewed, with particular attention paid to ß-carotene and lycopene, but also including ß-cryptoxanthin, lutein, zeaxanthin, and astaxanthin. The effect of beta-carotene oxygenase 1 and 2 knock-out mice on hepatic lipid metabolism is also discussed. In general, there is evidence to suggest that carotenoids have beneficial effects in animal models of both NAFLD and ALD. Mechanistically, these benefits may occur via three possible modes of action: 1) improved hepatic antioxidative status broadly attributed to carotenoids in general, 2) the generation of vitamin A from ß-carotene and ß-cryptoxanthin, leading to improved hepatic retinoid signaling, and 3) the generation of apocarotenoid metabolites from ß-carotene and lycopene, that may regulate hepatic signaling pathways. Gaps in our knowledge regarding carotenoid mechanisms of action in the liver are highlighted throughout, and the review ends by emphasizing the importance of dose effects, mode of delivery, and mechanism of action as important areas for further study. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.

Myrciaria dubia, an Amazonian fruit: population structure and its implications for germplasm conservation and genetic improvement.

Myrciaria dubia (camu-camu) is an Amazon tree that produces a tart fruit with high vitamin C content. It is probably the fruit with the highest vitamin C content among all Brazilian fruit crops and it can be used to supplement daily vitamin C dose. This property has attracted the attention of consumers and, consequently, encouraged fruit farmers to produce it. In order to identify and select potential accessions for commercial exploitation and breeding programs, M. dubia has received considerable research attention. The identification and characterization of genetic diversity, as well as identification of the population structure of accessions preserved in germplasm banks are fundamental for the success of any breeding program. The objective of this study was to evaluate the genetic variability of 10 M. dubia populations obtained from the shores of Reis Lake, located in the municipality of Caracaraí, Roraima, Brazil. Fourteen polymorphic inter simple sequence repeat (ISSR) markers were used to study the population genetic diversity, which resulted in 108 identified alleles. Among the 14 primers, GCV, UBC810, and UBC827 produced the highest number of alleles. The study illustrated the suitability and efficiency of ISSR markers to study the genetic diversity of M. dubia accessions. We also revealed the existence of high genetic variability among both accessions and populations that can be exploited in future breeding programs and conservation activities of this species.

ß-carotene-producing bacteria residing in the intestine provide vitamin A to mouse tissues in vivo.

Vitamin A deficiency (VAD) is an overwhelming public health problem that affects hundreds of millions of people worldwide. A definitive solution to VAD has yet to be identified. Because it is an essential nutrient, vitamin A or its carotenoid precursor ß-carotene can only be obtained from food or supplements. In this study, we wanted to establish whether ß-carotene produced in the mouse intestine by bacteria synthesizing the provitamin A carotenoid could be delivered to various tissues within the body. To achieve this, we took advantage of the Escherichia coli MG1655*, an intestine-adapted spontaneous mutant of E. coli MG1655, and the plasmid pAC-BETA, containing the genes coding for the 4 key enzymes of the ß-carotene biosynthetic pathway (geranylgeranyl pyrophosphate synthase, phytoene synthase, phytoene desaturase, and lycopene cyclase) from Erwinia herbicola. We engineered the E. coli MG1655* to produce ß-carotene during transformation with pAC-BETA (MG1655*-ßC) and gavaged wild-type and knockout mice for the enzyme ß-carotene 15,15'-oxygenase with this recombinant strain. Various regimens of bacteria administration were tested (single vs. multiple and low vs. high doses). ß-Carotene concentration was measured by HPLC in mouse serum, liver, intestine, and feces. Enumeration of MG1655*-ßC cells in the feces was performed to assess efficiency of intestinal colonization. We demonstrated in vivo that probiotic bacteria could be used to deliver vitamin A to the tissues of a mammalian host. These results have the potential to pave the road for future investigations aimed at identifying alternative, novel approaches to treat VAD.

Bioaccessibility of carotenoids from transgenic provitamin A biofortified sorghum.

Biofortified sorghum (Sorghum bicolor (L.) Moench) lines are being developed to target vitamin A deficiency in Sub-Saharan Africa, but the delivery of provitamin A carotenoids from such diverse germplasms has not been evaluated. The purpose of this study was to screen vectors and independent transgenic events for the bioaccessibility of provitamin A carotenoids using an in vitro digestion model. The germplasm background and transgenic sorghum contained 1.0-1.5 and 3.3-14.0 µg/g ß-carotene equivalents on a dry weight basis (DW), respectively. Test porridges made from milled transgenic sorghum contained up to 250 µg of ß-carotene equivalents per 100 g of porridge on a fresh weight basis (FW). Micellarization efficiency of all-trans-ß-carotene was lower (p < 0.05) from transgenic sorghum (1-5%) than from null/nontransgenic sorghum (6-11%) but not different between vector constructs. Carotenoid bioaccessibility was significantly improved (p < 0.05) by increasing the amount of coformulated lipid in test porridges from 5% w/w to 10% w/w. Transgenic sorghum event Homo188-A contained the greatest bioaccessible ß-carotene content, with a 4-8-fold increase from null/nontransgenic sorghum. While the bioavailability and bioconversion of provitamin A carotenoids from these grains must be confirmed in vivo, these data support the notion that biofortification of sorghum can enhance total and bioaccessible provitamin A carotenoid levels.

Situação alimentar de crianças entre zero e dois anos atendidas em programa de saúde da família no sul do estado de Santa Catarina / Alimentary situation of children from zero to two years old inserted in the family health program in the south of Santa Catarina state

Objetivo: Descrever o padrão de alimentação de lactentes em comunidade no sul de Santa Catarina eanalisar fatores associados, tais como, realização da puericultura, tempo de amamentação e suplementação de ferro e vitaminas A e D. Métodos: Estudo transversal, realizado com 160 mães de crianças com até dois anos de idade do bairro São Martinho, cidade de Tubarão, Santa Catarina. Foi realizada entrevista dirigida, contendo dados referentesà alimentação, realização de puericultura e suplementação vitamínica. Os dados foram analisados pelo programa SPSS12.0, através do teste chi- quadrado e t-studentcom significância de 95%. Resultados: Foi encontrada uma prevalência de aleitamento materno exclusivo de 90% no primeiro mês, 30% do segundo ao sexto mês e 30 % de aleitamento materno complementado até os dois anos. Com relação à puericultura,78,1% das mães realizaram ou a estavam realizando em seus filhos. O leite de vaca foi o preferido em 80% dos casos de desmame. A utilização do mesmo, assim como a suplementação de vitaminas A e D e de ferro, não foram influenciados pela realização de puericultura (p=0,38). Conclusão: O estudo encontrou boa prevalência dealeitamento materno, porém uma baixa taxa de suplementação de ferro e vitamina A e D e com grande utilizaçãode leite de vaca in natura no desmame.

Objective: To describe the standard feeding of suckles in a community in the south of Santa Catarina and to study factors associated as the well-child care, duration of breast-feeding and A and D vitamin and iron feedingsupplements. Methods: A cross-sectional study was realized with 160 mothers of children up to two years old of age inSão Martinho, suburb of the city of Tubarão, Santa Catarina. A directed interview was applied containing questions regarding the child’s diet, well-child care and vitamin supplementation. Data was analyzed trough statisticalprogram SPSS 12.0, using chi-square and t-student tests, with significance level of 95%. Results: A prevalence of 90% of exclusive maternal breast-feeding in the first month, 30% in the second month and 30% of complemented maternal breast-feedinguntil de second year of age was found. In regards to well-child care, 78.1% the mothers had carried it out or were carrying though during the time of the interview. Cow milk was the preferred substitute in 80% of the weaning cases. The use of the same, as well as theuse of A and D vitamins and iron supplements, were not influenced by the realization of well-child care (p=0,38).Conclusion: The study found an important prevalence of maternal breast-feeding, however a low rate of A and D vitamin and iron feeding supplements, with great use of whole cow milk in the weans.

[Evaluation on beta-carotene-vitamin A equivalence of middle-aged subjects in Chinese adults].

OBJECTIVE: As an extended study of beta-Carotene-vitamin A equivalence in Chinese adults, we carried out an experiment on 10 (5 males and 5 females) rural volunteers aged 38 - 49 years, which would be complementary to the early reported study on subjects aged 50 - 60 years. METHODS: Ten healthy Chinese adult volunteers aged 38-49 years were recruited in a 56 days experiment, which included residency in the Metabolic Research Unit (first 10 days and in home (last 46 days). A physiological dose of 2H8 beta-C (11,011 (nmole or 6 mg) in oil was given with a liquid diet (25% energy from fat) to the volunteers in the first day of the experiment. Three days after the 2H8 beta-C, each volunteer took a reference dose of 2H8 retinyl acetate (8,915 nmole or 3 mg) in oil with the same liquid diet. Serum samples were collected at 0, 3, 5, 7, 9, 11 and 13 hours of the first and the fourth days of study, and fasting serum samples were also collected daily in first 10 days and then weekly at morning of 14th, 21st, 28th, 35th, 42nd, 49th and 56th day after a 12-hours overnight fast. Serum retinol and carotenoids concentrations were measured by high performance liquid chromatography (HPLC). Also retinol fraction was extracted from serum and isolated by HPLC. The serum retinal enrichments were determined by using gas chromatograph/mass spectrometry with electron capture negative chemical ionization (GC-MS). RESULTS: The average 52-day area under the serum 2H4 retinol response curve (from the 2H8 beta-C dose) was (1289 +/- 547) nmol/d and the 52-day area under the serum 2H8 retinol response curve (from the 2H8 retinyl acetate dose) was (3560 +/- 1058) nmol/d. By using 2H8 retinyl acetate as the vitamin A reference, the 2H4 retinol formed from 2H8 beta-C (11,011 nmol) was calculated to be equivalent to (3434 +/- 1449) nmol of retinol. The calculated conversion factor of beta-C to retinol ranged from 2.00 - 9.61 to 1 with an average of (3.89 +/- 2.76) to 1 on a molar basis, or 3.76 - 18.05 to 1 with an average of (7.30 +/- 5.18) to 1 on a weight basis. CONCLUSION: The conversion of beta-C to vitamin A in 10 middle-aged Chinese adults had been quantitatively determined by using a stable isotope reference method, and an average conversion ratio of 7.30 : 1 to 1 on a weight basis was found in this study.

Absorption and conversion of a single oral dose of beta-carotene in corn oil to vitamin A in Sprague-Dawley rats with low reserve of vitamin A.

This study was carried out to determine how much of a single oral dose of beta-carotene in oil is absorbed and how much of the absorbed dose is converted to retinoids in rats having a vitamin A reserve at the lowest end of adequate status. Weanling rats raised on a vitamin A-deficient diet for four weeks were given a single oral dose of either corn oil or beta-carotene dissolved in corn oil (1.86 mumol). Serum, liver, and the entire digestive tract of the rats were analyzed for carotenoids and retinoids. Results showed that 4 hours after dosing, 1.64 mumol (88%) of the dose of beta-carotene was found intact, with 17.6% found in the stomach, 21% in the small intestine, and 49.3% in the large intestine. A total of 0.28 mumol of newly formed retinoids (expressed as retinyl palmitate) was present in serum, liver, and mucosa of small intestine. The results suggest that a single oral dose of beta-carotene might not be an effective way of raising vitamin A status in rats.

Absorption and conversion of 11,12-(3)H-beta-carotene to vitamin A in Sprague-Dawley rats of different vitamin A status.

The aim of this study was to determine the bioavailability and bioconversion to vitamin A of a single oral dose in oil or an aqueous dispersion of labeled beta-carotene in rats of different vitamin A status. Weanling Sprague-Dawley rats were fed a vitamin A-deficient diet and supplemented for 4 wk with 0, 7, 21 and 63 micro g/(rat. d) of retinyl acetate. The rats, of different vitamin A status, were then given a single oral dose of 11,12-(3)H-beta-carotene (0.15 micro mol) dissolved in corn oil or dispersed in aqueous Tween 80. The rats were killed 4 or 24 h after the dose, and serum, liver, the entire digestive tract, other tissues, urine and feces were analyzed for carotenoids, retinoids and associated radioactivity. At 4 h after the dose, 85 +/- 9% of the administered radioactivity was recovered. Almost 50% of the dose was present as intact beta-carotene in the large intestine where further absorption and conversion was ruled out. The absorption of beta-carotene was very low, and < 5% of the radioactive dose was converted to retinoids. The absorption and conversion to vitamin A did not differ among rats of different vitamin A status. The results suggest that a single oral dose of beta-carotene might not be an effective way of raising vitamin A stores in the body.

Biochemical properties of purified recombinant human beta-carotene 15,15'-monooxygenase.

Beta-carotene 15,15'-monooxygenase (BCO), formerly known as beta-carotene 15,15'-dioxygenase, catalyzes the first step in the synthesis of vitamin A from dietary carotenoids. We have biochemically and enzymologically characterized the purified recombinant human BCO enzyme. A highly active BCO enzyme was expressed and purified to homogeneity from baculovirus-infected Spodoptera frugiperda 9 insect cells. The K(m) and V(max) of the enzyme for beta-carotene were 7 microm and 10 nmol retinal/mg x min, respectively, values that corresponded to a turnover number (k(cat)) of 0.66 min(-1) and a catalytic efficiency (k(cat)/K(m)) of approximately 10(5) m(-1) x min(-1). The enzyme existed as a tetramer in solution, and substrate specificity analyses suggested that at least one unsubstituted beta-ionone ring half-site was imperative for efficient cleavage of the carbon 15,15'-double bond in carotenoid substrates. High levels of BCO mRNA were observed along the whole intestinal tract, in the liver, and in the kidney, whereas lower levels were present in the prostate, testis, ovary, and skeletal muscle. The current data suggest that the human BCO enzyme may, in addition to its well established role in the digestive system, also play a role in peripheral vitamin A synthesis from plasma-borne provitamin A carotenoids.

Expression of retinoid-related genes in serum-free cultures of normal, immortalized and malignant human oral keratinocytes.

Retinoids are used in the clinical treatment of oral squamous carcinoma, including both early and late stages. Inter-individual variation in responsiveness, including a common insensitivity of advanced stages, suggest that changes in retinoid-related functions might characterize tumor development. To investigate a genetic basis for this hypothesis, an in vitro multi-step model of carcinogenesis involving normal (NOK), SV40 T antigen-immortalized (SVpgC2a) and malignant (SqCC/Y1) oral keratinocytes was analysed under identical culture conditions using micro-array technique (Affymetrix HG_U95A chip) for expression of 52 genes related to retinoid metabolism and actions. The variable detection of between 22-26 transcripts in the cell lines, involving binding/transport factors, receptors, transcriptional activators/repressors and responsive genes, indicated specificity in regards to the expression of known retinoid-related genes in oral keratinocytes. The transformed cell lines variably exhibited differences as compared to NOK, i.e., lower transcript levels for cellular retinol binding protein, the cellular retinoic acid binding protein II (CRABP II) and retinoic acid receptor gamma, whereas in contrast, the levels of CRABP I were higher. Transcripts for proteins interacting with nuclear retinoid receptors were similarly expressed among the cell types, whereas transcripts for retinoid-metabolizing enzymes were generally not detected. Finally, transcripts of retinoid-responsive genes, including RARRES3, RI58, NN8-4AG and midkine, were variably expressed. The overall results imply selective expression of retinoid-related functions in normal and transformed keratinocytes, and that cell transformation can impair the capacity for binding and storage of retinol as well as retinoic acid-mediated signalling. These multiple alterations are consistent with possible retinoid insensitivity during oral carcinogenesis.

Molecular analysis of vitamin A formation: cloning and characterization of beta-carotene 15,15'-dioxygenases.

Beta-carotene 15,15'-dioxygenase cleaves beta-carotene into two molecules of retinal and is the key enzyme in the metabolism of carotene to vitamin A. Although the enzyme has been known for more than 40 years, all attempts to purify the protein to homogeneity or to clone its gene have failed until recently, when the successful cloning and sequencing of cDNAs encoding enzymes with beta-carotene 15,15'-dioxygenase activity from Drosophila (J. von Lintig and K. Vogt, 2000, J. Biol. Chem. 275, 11915-11920) and chicken (A. Wyss et al., 2000, Biochem. Biophys. Res. Commun. 271, 334-336) were reported. Very soon it became clear, that we have cloned two members of a new family of carotenoid cleaving enzymes. Overall homologies are very high, certain amino acid stretches almost identical. Thus, beta-carotene 15,15'-dioxygenase can be considered as evolutionarily well conserved. These findings open up wide perspectives for further analysis of this important biosynthetic pathway, concerning basic and medical research as well as biotechnological aspects related to vitamin A supply, which are discussed here.

Nutritional status affects intestinal carotene cleavage activity and carotene conversion to vitamin A in rats.

Validation of an in vivo method we developed recently and its application to assess the role of dietary factors in carotene conversion were tested in rats. We compared the ratio of area under plasma vitamin A time-curves (AUC(0-12h)) obtained after a dose of beta-carotene to that after a dose of vitamin A, with the in vitro intestinal supernatant beta-carotene dioxygenase activity. In separate experiments, vitamin A (AD) and protein deficiencies (PD) were produced in male WNIN weanling rats. Corresponding food-restricted (AR and PR) and unrestricted rats (AA and PA) served as controls. Three rats in each of the AD, AR and AA groups received oral doses of 50-300 microgram beta-carotene or 25-150 microgram vitamin A and four rats in each of the PD, PR and PA groups received only 100 microg beta-carotene or vitamin A. The plasma vitamin A AUC(0-12h) with beta-carotene or vitamin A were significantly and positively correlated (r = 0.714-0.918, n = 9-12, P < 0.05) with the dose in AD, AR and AA groups. The AUC(0-12h) slope ratios in AD, AR and AA rats were 0.33, 0.20 and 0.26, respectively. The beta-carotene dioxygenase activity (pmol retinal. h(-1). mg protein(-1)) was significantly higher in the AD group (14.9 +/- 2.43) compared to both AR (6.7 +/- 0.62) and AA (6.3 +/- 1.37) groups and was parallel with in vivo conversion of beta-carotene to vitamin A. The AUC(0-12h) ratio was lower in PD rats (0.13) compared to PR (0.26) and PA (0.5) groups. Similarly, the in vitro enzyme activity (pmol retinal. h(-1). mg protein(-1)) in PD rats was significantly lower (3.6 +/- 1.30) compared to PR (13.7 +/- 0.92) and PA groups (13.8 +/- 1.6). Thus the results validate the methodology and confirm the role of nutritional factors in carotene conversion to vitamin A.

Biochemical properties, tissue expression, and gene structure of a short chain dehydrogenase/ reductase able to catalyze cis-retinol oxidation.

We have identified a retinol dehydrogenase (cRDH) that catalyzes the oxidation of 9-cis- but not all-trans-retinol and proposed that this enzyme plays an important role in synthesis of the transcriptionally active retinoid, 9-cis-retinoic acid. There is little information regarding either the biochemical properties of cRDH or how its 9-cis-retinol substrate is formed. We now report studies of the properties and expression of human and mouse cRDH and of the characteristics and location of the murine cRDH gene. Additionally, we report mouse hepatic 9-cis-retinol concentrations and demonstrate that 9-cis-retinol is formed in a time- and protein-dependent manner upon incubation of all-trans -retinol with cell homogenate. Human and mouse cRDH display similar substrate specificities for cis-isomers of retinol and retinaldehyde. Moreover, human and mouse cRDH show marked sensitivity to inhibition by 13-cis-retinoic acid, with both being inhibited by approximately 50% by 0.15 microm 13-cis-retinoic acid (for substrate concentrations of 10 microm). Lesser inhibition is seen for 9-cis- or all-trans-retinoic acids. Immunoblot analysis using antiserum directed against human cRDH demonstrates cRDH expression in several tissues from first trimester human fetuses, indicating that cRDH is expressed early in embryogenesis. Adult mouse brain, liver, kidney, and to a lesser extent small intestine and placenta express cRDH. The murine cRDH gene consists of at least 5 exons and spans approximately 6 kb of genomic DNA. Backcross analysis mapped the mouse cRDH gene to the most distal region of chromosome 10. Taken together, these data extend our understanding of the properties of cRDH and provide additional support for our hypothesis that cRDH may play an important role in 9-cis-retinoic acid formation.

Enrichment of the diet with synthetic and natural sources of provitamin A.

The use of available food rich in provitamin A and retinol as well as fortification of local food are known to result in adequate vitamin A status. In Brazil, several regional foods are known to be good sources of provitamin A such as buriti, several palm oils, mango and others. Improving the consumption of these locally available natural sources of provitamin and vitamin A would cover the needs of the vulnerable population. At the same time fortification of industrialized foods with natural and/or synthetic forms of provitamin A could speed up and fill the gap between requirement and low intake of this vitamin in many parts of the country. This approach has been considered by many as the most effective intervention program to prevent micronutrient deficiencies in developing countries. Our previous studies on the subject have shown that cooking vegetable oil, mainly soybean oil, is a very good alternative vehicle to be fortified and supply vitamin A to the population. Lately we have also enriched the same soybean oil with beta-carotene. Addition of this provitamin A to the oil showed it to be stable when heated at cooking and frying temperatures (retention of 92.4 +/- 6.7% and 65.4 +/- 8.6%, respectively). When rat or human food was prepared with carotene-enriched cooking oil, its bioavailability in experimental animals and absorption in humans were shown to be adequate. An alternative for Brazil, besides adding chemical forms of the vitamin to the cooking oil, would be to mix available carotene-rich palm oil to the soybean oil. There are already regional uses of carotenoid-rich palm oils in the preparation of local dishes in some parts of Brazil and this would facilitate its acceptance by the population. Enrichment of common foods in Brazil, such as soybean oil, with chemical forms of beta-carotene or mixing rich sources of provitamin A can be a good alternative to improve the intake of vitamin A by the Brazilian population.

Formation and storage of 11-cis retinol in the eyes of lobster (Homarus) and crayfish (Procambarus).

Modes of storage and mechanisms of formation of 11-cis retinoids in the eyes of animals vary widely among the major phyla. We here describe evidence from two species of macruran decapod crustacea that point to different processes from those known in insects, the other group of arthropods for which there is extensive data. The eyes of the lobster (Homarus) contain about 300 pmol of retinal, somewhat less free retinol, and variable amounts (up to 1000+ pmol) of two retinyl esters, over 90% of which contain retinol in the 11-cis configuration. The major ester contains the long chain, polyunsaturated fatty acid docosahexaenoate (C22:6), but retinyl oleate (C18:1) is also present. Crayfish (Procambarus) contain the same retinyl esters, although in much smaller amounts. Homogenates of the eyes of both species are capable of isomerizing all-trans retinyl docosahexaenoate to the 11-cis configuration without using the energy of light. Crude fractionation of homogenates shows isomerase activity associated with membranes. The reaction mechanism has not been explored in detail, but on the basis of present evidence it may be similar to that found in vertebrate pigment epithelium. It is clearly different from the light-dependent processes known in insects (Hymenoptera and Diptera) and cephalopod mollusks, where isomerization takes place at the level of the aldehyde and 11-cis retinyl esters are not present as major storage reserves.

Biological actions of carotenoids.

Of 600 carotenoids from natural sources that have been characterized, fewer than 10% serve as precursors of vitamin A. Many dietary carotenoids, both with and without provitamin A activity, are found in the blood and tissues of humans. beta-Carotene, the most nutritionally active carotenoid, comprises 15-30% of total serum carotenoids. Vitamin A is formed primarily by the oxygen-dependent central cleavage of beta-carotene and other provitamin A carotenoids. Several carotenoids show enhancement of the immune response, inhibition of mutagenesis, reduction of induced nuclear damage, and protection from various neoplastic events in cells, tissues, and whole animals. Carotenoids also protect against photo-induced tissue damage. Some carotenoids, including beta-carotene, quench highly reactive singlet oxygen under certain conditions and can block free radical-mediated reactions. In epidemiological studies, the intake of carotenoid-rich fruits and vegetables has been correlated with protection from some forms of cancer, particularly lung cancer. Similarly, serum beta-carotene levels have been associated with a decreased chance of developing lung cancer. It must be stressed, however, that these epidemiological associations do not show cause and effect. In this regard, long-term intervention trials with beta-carotene supplements are in progress. Whatever the results of these trials, carotenoids clearly show biological actions in animals distinct from their function as precursors of vitamin A.