Mitigation of Huanglongbing: Implications of a Biologically Enhanced Nutritional Program on Yield, Pathogen Localization, and Host Gene Expression Profiles

Huanglongbing (HLB, citrus greening disease), the most destructive disease affecting citrus production, is primarily linked to the gram-negative, insect-vectored, phloem-inhabiting α-proteobacterium 'Candidatus Liberibacter asiaticus' (CLas). With no effective treatment available, management strategies have largely focused on the use of insecticides in addition to the destruction of infected trees, which are environmentally hazardous and cost-prohibitive for growers, respectively. A major limitation to combating HLB is the inability to isolate CLas in axenic culture, which hinders in vitro studies and creates a need for robust in situ CLas detection and visualization methods. The aim of this study was to investigate the efficacy of a nutritional program-based approach for HLB treatment, and to explore the effectiveness of an enhanced immunodetection method to detect CLas-infected tissues. To achieve this, four different biologically enhanced nutritional programs (bENPs; P1, P2, P3, and P4) were tested on CLas-infected citrus trees. Structured illumination microscopy preceded by a modified immunolabeling process and transmission electron microscopy were used to show treatment-dependent reduction of CLas cells in phloem tissues. No sieve pore plugging was seen in the leaves of P2 trees. This was accompanied by an 80% annual increase in fruit number per tree and 1,503 (611 upregulated and 892 downregulated) differentially expressed genes. These included an MLRQ subunit gene, UDP-glucose transferase, and genes associated with the alpha-amino linolenic acid metabolism pathway in P2 trees. Taken together, the results highlight a major role for bENPs as a viable, sustainable, and cost effective option for HLB management.

Protective Effects of Chlorella vulgaris Supplemented Diet on Antibacterial Activity and Immune Responses in Rohu Fingerlings, Labeo rohita (Hamilton), Subjected to Aeromonas hydrophila Infection

The current study focuses on the antibacterial activity and potential efficiency of dietary supplements of Chlorella vulgaris on the immune response, improved growth performance, and disease resistance of Labeo rohita fingerlings against Aeromonas hydrophila infection. Crude ethanolic extract of Chlorella and partially purified fractions of the extract were tested against two selected fish pathogens using the disc diffusion method. A total number of 360 rohu fingerlings (25 ± 2 g) were allocated to 4 treatments for 90 days. They were fed with an experimental diet containing Chlorella powder (0, 0.1, 0.5, and 1.0 g Kg^-1 of a basic diet). To evaluate the non-specific immunity parameters including serum bactericidal, lysozyme activity, superoxide anion production, and biochemical and haematological indices, the fish were sampled at day 30, 60, 90, and after bacterial challenge. Mortalities of the fish were observed over 10 days post challenge with A. hydrophila. The protein and globulin levels of the treatment group were significantly higher after being treated with Chlorella than those of the control group. The total blood-cell count and haemoglobin content were also increased in the algal-diet-treated group. Among all the experimental diets, the 0.5 g Kg^-1Chlorella fed group of fish showed significantly (p < 0.05) increased serum bactericidal activity and superoxide anion production when compared with the control group on day 90. Maximum lysozyme activity (750.00 ± 3.27) was noticed in the 1.0 g Kg^-1 diet fed group on day 30. The Chlorella treated group exhibited a better growth performance of the fish. The maximum survivability (86.5%) was recorded in the 1.0 g Kg^-1 diet fed group at the end of the 10-day fish exposure to A. hydrophila. These results suggest that the optimum dietary Chlorella supplementation could be 0.5-1.0 g Kg^-1 of the diet, which stimulates immunity and protects L. rohita from A. hydrophila infection.

A small molecule compound that inhibits blue light-induced retinal damage via activation of autophagy

Dry age-related macular degeneration (AMD) is a type of disease that causes visual impairment due to changes in the macula located in the center of the retina. The accumulation of drusen under the retina is also a characteristic of dry AMD. In this study, we identified a compound (JS-017) that can potentially degrade N-retinylidene-N-retinylethanolamine (A2E), one of the components of lipofuscin, using fluorescence-based screening, which measures A2E degradation in human retinal pigment epithelial cells. JS-017 effectively degraded A2E in ARPE-19 cells and consequently suppressed the activation of the NF-κB signaling pathway and expression of inflammatory and apoptosis genes induced by blue light (BL). Mechanistically, JS-017 induced LC3-II formation and improved autophagic flux in ARPE-19 cells. Additionally, the A2E degradation activity of JS-017 was found to be decreased in autophagy-related 5 protein-depleted ARPE-19 cells, suggesting that autophagy was required for A2E degradation mediated by JS-017. Finally, JS-017 exhibited an improvement in BL-induced retinal damage measured through fundus examination in an in vivo retinal degeneration mouse model. The thickness of the outer nuclear layer and inner/external segments, which was decreased upon exposure to BL irradiation, was also restored upon JS-017 treatment. Altogether, we demonstrated that JS-017 protected human retinal pigment epithelium (RPE) cells from A2E and BL-induced damage by degrading A2E via the activation of autophagy. The results suggest the feasibility of a novel A2E-degrading small molecule as a therapeutic agent for retinal degenerative diseases.

Chlorella vulgaris ameliorates sodium nitrite-induced hepatotoxicity in rats

The current was conducted to evaluate the ameliorating effect of Chlorella vulgaris (CV) extract against sodium nitrite-induced hepatotoxicity in rats. Forty-five rats were allocated randomly into 5 groups (n = 9). Group I (GI), control group: orally gavaged with normal saline daily. Group II (GII): orally gavaged with CV extract (70 mg/kg BW) for 3 months. Group III (GIII): orally gavaged with sodium nitrite (80 mg/kg BW) for 3 months. Group IV (GIV): received sodium nitrite as GIII and CV extract as GII simultaneously for 3 months. Group V (GV): received CV extract as GII and then, sodium nitrite as in GIII from the end of first month until the end of the experiment. Sodium nitrite significantly increased the activities of serum alanine aminotransferase, aspartate aminotransferase, and serum concentrations of tumor interleukin 1-β and necrosis factor α. In addition, it increased concentrations of malondialdehyde and nitric oxide and expression level of caspase-3 in the hepatic tissue. However, it decreased activities of hepatic glutathione peroxidase, catalase, and superoxide dismutase and induced degenerative and necrotic changes in hepatic tissues. In contrast, CV extract administration modulated sodium nitrite-induced inflammation, oxidative stress, and alteration in hepatic tissue function and architecture. This study indicated that CV extract modulated sodium nitrite-induced hepatic toxicity through decreasing oxidative stress and inflammation and enhancing antioxidant enzyme activities in hepatic tissue of rats.

Functional Characterization of Marigold Powder as a Food Ingredient for Lutein-Fortified Fresh Noodles

Marigold powder was utilized as a food ingredient to produce lutein-fortified fresh noodles for eye health, and its functionalities were characterized in terms of thermo-rheological, structural, and antioxidant properties. The pasting parameters and starch-gelatinization enthalpy values of wheat flour had a tendency to decrease with increasing levels of marigold powder. The use of marigold powder led to decreases in the storage and loss moduli of wheat flour pastes by weakening their cellular microstructure, which was confirmed by the scanning electron microscopic images. When marigold powder was incorporated into the formulation of fresh noodles, the cooking loss and water absorption of the noodles were not negatively affected at a level of 2% (w/w). Also, the noodles with 2% marigold powder were not significantly different from the control for the maximum resistance to extension. The levels of lutein in the noodles prepared with marigold powder (61.2 to 204.9 mg/100 g) were reduced by almost 50% after cooking. However, they seemed to satisfy the recommended daily dose of lutein for visual functions. Moreover, the use of marigold powder provided antioxidant properties for noodles by enhancing the 2,2′-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical-scavenging activities.

Chemoprotective effect of carotenoids from Lycium barbarum L. on SH-SY5Y neuroblastoma cells treated with beauvericin

Goji berry has recently been introduced in Mediterranean diet and its consumption is increasing. This study aims to determine cytoprotection of lutein (LUT), zeaxanthin (ZEAX) and goji berry extract (GBE) rich in carotenoids against Beauvericin (BEA)-induced cytotoxicity on SH-SY5Y neuroblastoma cells. Both carotenoids and GBE showed cytoprotective effects. Cytoprotection was evaluated by simultaneous combination of the two xanthophylls LUT and ZEAX with BEA, as well as using pre-treatment assays. The highest protective effect occurred in 16%, 24% and 12% respectively for LUT, ZEAX and LUT + ZEAX incubating simultaneously with BEA, while by pre-treatment assay LUT showed a cytoprotection effect over 30% and ZEAX alone or LUT + ZEAX promoted only a slight cytoprotection (<10%). Pre-treatment assays with GBE, showed a cytoprotection, between 3 and 20%, for BEA concentrations ranging from 0.1 to 6.25 μM, whereas no protective effect was observed when the cells were simultaneously incubated with GBE and BEA. Finally, by means of CI-isobologram method, the interaction between LUT, ZEAX and BEA were evaluated, and the results showed an synergism effect for almost all combinations tested. The data presented shows a option of using goji berries to potentially mitigate the toxicity of beauvericin eventually present in foods.

Nutrients for Prevention of Macular Degeneration and Eye-Related Diseases

The risk of macular degeneration can be reduced through the consumption of antioxidant-rich foods, supplements, and nutraceutical formulas. This review focuses on the antioxidants, vitamins, and minerals that have been reported for reducing the risk of macular degeneration and other eye-related diseases. Antioxidants including anthocyanins, carotenoids, flavonoids, and vitamins have been shown to reduce the risk of eye-related diseases. Anthocyanins extracted from berries are powerful antioxidants. Cyanidin, delphinidin, malvidin, pelargonidin, peonidin, and petunidin are anthocyanin aglycones detected in berries, currants, and other colored fruits and vegetables. β-Carotene, as well as xanthophyll lutein and zeaxanthin, have been reported to reduce the risk of macular degeneration. Flavonoids from plants help in the prevention of eye-related diseases through anti-inflammatory mechanisms. A combination of these antioxidants, vitamins, and minerals possess a synergistic effect on the prevention or risk reduction of macular degeneration. Formulas have been developed as dietary supplements to cater to the high demand from consumers and patients with eye problems. Many of the formulated dietary supplements that are sold in the market have been clinically proven for their efficacy to treat eye diseases. Although the bioactivities in the supplement capsules or tablets have been scientifically established for reducing risks of several diseases, which include macular degeneration and other eye-related diseases, knowledge on the right dosage, efficacy, and bioavailability of antioxidants, vitamins, and minerals is important for consumers. The information may help them make the best decision in choosing the right dietary supplements and nutraceuticals following the evidence-based recommended dosages and reference intakes for improving general health and preventing eye-related diseases. This review covers the potential causal factors involved in eye diseases, clinically proven treatments, and controversial findings on the antioxidants in the prevention of macular degeneration. Future studies should consider multiethnic and multicenter trials for eliminating potential bias in research.

Optimizing the localization of astaxanthin enzymes for improved productivity

BACKGROUND

One important metabolic engineering strategy is to localize the enzymes close to their substrates for improved catalytic efficiency. However, localization configurations become more complex the greater the number of enzymes and substrates is involved. Indeed, optimizing synthetic pathways by localizing multiple enzymes remains a challenge. Terpenes are one of the most valuable and abundant natural product groups. Phytoene, lycopene and β-carotene serve as common intermediates for the synthesis of many carotenoids and derivative compounds, which are hydrophobic long-chain terpenoids, insoluble in water and usually accumulate in membrane compartments.

RESULTS

While β-ionone synthesis by β-carotene cleavage dioxygenase PhCCD1 and astaxanthin synthesis by β-carotene ketolase (CrtW) and β-carotene hydroxylase (CrtZ) differ in complexity (single and multiple step pathways), the productivity of both pathways benefited from controlling enzyme localization to the E. coli cell membrane via a GlpF protein fusion. Especially, the astaxanthin synthesis pathway comprises both CrtW and CrtZ, which perform four interchangeable reactions initiated from β-carotene. Up to four localization strategies of CrtW and CrtZ were exhaustively discussed in this work, and the optimal positioning strategy was achieved. CrtW and CrtZ were linked using a flexible linker and localized to the membrane via a GlpF protein fusion. Enzymes in the optimal localization configuration allowed a 215.4% astaxanthin production increase.

CONCLUSIONS

This work exploits a localization situation involving membrane-bound substrates, intermediates and multiple enzymes for the first time, and provides a workable positioning strategy to solve problems in similar circumstances.

In Vitro Inhibition of Human UDP-Glucuronosyl-Transferase (UGT) Isoforms by Astaxanthin, β-Cryptoxanthin, Canthaxanthin, Lutein, and Zeaxanthin: Prediction of in Vivo Dietary Supplement-Drug Interactions

Despite the widespread use of the five major xanthophylls astaxanthin, β-cryptoxanthin, canthaxanthin, lutein, and zeaxanthin as dietary supplements, there have been no studies regarding their inhibitory effects on hepatic UDP-glucuronosyltransferases (UGTs). Here, we evaluated the inhibitory potential of these xanthophylls on the seven major human hepatic UGTs (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B7 and UGT2B15) in vitro by LC-MS/MS using specific marker reactions in human liver microsomes (except UGT2B15) or recombinant supersomes (UGT2B15). We also predicted potential dietary supplement-drug interactions for β-cryptoxanthin via UGT1A1 inhibition. We demonstrated that astaxanthin and zeaxanthin showed no apparent inhibition, while the remaining xanthophylls showed only weak inhibitory effects on the seven UGTs. β-Cryptoxanthin mildly inhibited UGT1A1, UGT1A3, and UGT1A4, with IC50 values of 18.8 ± 2.07, 28.3 ± 4.40 and 34.9 ± 5.98 μM, respectively. Canthaxanthin weakly inhibited UGT1A1 and UGT1A3, with IC50 values of 38.5 ± 4.65 and 41.2 ± 3.14 μM, respectively; and lutein inhibited UGT1A1 and UGT1A4, with IC50 values of 45.5 ± 4.01 and 28.7 ± 3.79 μM, respectively. Among the tested xanthophyll-UGT pairs, β-cryptoxanthin showed the strongest competitive inhibition of UGT1A1 (Ki, 12.2 ± 0.985 μM). In addition, we predicted the risk of UGT1A1 inhibition in vivo using the reported maximum plasma concentration after oral administration of β-cryptoxanthin in humans. Our data suggests that these xanthophylls are unlikely to cause dietary supplement-drug interactions mediated by inhibition of the hepatic UGTs. These findings provide useful information for the safe clinical use of the tested xanthophylls.

Biologically Active Metabolites Synthesized by Microalgae

Microalgae are microorganisms that have different morphological, physiological, and genetic traits that confer the ability to produce different biologically active metabolites. Microalgal biotechnology has become a subject of study for various fields, due to the varied bioproducts that can be obtained from these microorganisms. When microalgal cultivation processes are better understood, microalgae can become an environmentally friendly and economically viable source of compounds of interest, because production can be optimized in a controlled culture. The bioactive compounds derived from microalgae have anti-inflammatory, antimicrobial, and antioxidant activities, among others. Furthermore, these microorganisms have the ability to promote health and reduce the risk of the development of degenerative diseases. In this context, the aim of this review is to discuss bioactive metabolites produced by microalgae for possible applications in the life sciences.

The use of heterochromatic flicker photometry to determine macular pigment optical density in a healthy Australian population

PURPOSE

To establish the normal macular pigment density (MPOD) in a healthy adult Australian sample using heterochromatic flicker photometry (HFP).

METHODS

Macular pigment density was measured using heterochromatic flicker photometry in a total of 201 subjects ranging in age from 21 to 84 years with healthy macula. Fifty-seven of the healthy subjects also completed a food-frequency dietary questionnaire. Best-corrected visual acuity (BCVA) was measured using logMAR, chart and macular morphological profiles were assessed using high-resolution integrated Fourier-domain optical coherence tomography (OCT).

RESULTS

The average MPOD value was 0.41 ± 0.20 (range 0.07-0.79). There was no statistically significant difference between values in the left and right eye, with good interocular agreement (0.41 vs 0.40, r = 0.893, p < 0.01). Age significantly predicted MPOD score (R (2) = 0.07, p < 0.05). A subgroup analysis of patients who completed the dietary questionnaire revealed a close correlation between higher diet scores and higher MPOD (r = 0.720 p = 0.031). There was no effect of smoking, gender, or iris colour on MPOD values. There was no significant correlation between BCVA, macular OCT profiles, and MPOD.

CONCLUSION

Given that MPOD values are potentially affected by geographical variation, we have determined a mean MPOD value for healthy subjects in a population south of the equator, providing a reference point for future studies on Caucasian samples.

New findings in ATP supply in rod outer segments: insights for retinopathies

BACKGROUND INFORMATION

The rod outer segment (OS) is the specialised organelle where phototransduction takes place. Our previous proteomic and biochemical analyses on purified rod disks showed the functional expression of the respiratory chain complexes I-IV and F1 Fo -ATP synthase in OS disks, as well as active soluble tricarboxylic acid cycle enzymes. Here, we focussed our study on the whole OS that contains the cytosol and plasma membrane and disks as native flattened saccules, unlike spherical osmotically intact disks.

RESULTS

OS were purified from bovine retinas and characterised for purity. Oximetry, ATP synthesis and cytochrome c oxidase (COX) assays were performed. The presence of COX and F₁F₀-ATP synthase (ATP synthase) was assessed by semi-quantitative Western blotting, immunofluorescence or confocal laser scanning microscopy on whole bovine retinas and bovine retinal sections and by immunogold transmission electron microscopy (TEM) of purified OS or bovine retinal sections. Both ATP synthase and COX are catalytically active in OS. These are able to consume oxygen (O₂) in the presence of pyruvate and malate. CLSM analyses showed that rhodopsin autofluorescence and MitoTracker Deep Red 633 fluorescence co-localise on rod OS. Data are confirmed by co-localisation studies of ATP synthase with Rh in rod OS by immunofluorescence and TEM in bovine retinal sections.

CONCLUSIONS

Our data confirm the expression and activity of COX and ATP synthase in OS, suggestive of the presence of an extra-mitochondrial oxidative phosphorylation in rod OS, meant to supply ATP for the visual transduction. In this respect, the membrane rich OS environment would be meant to absorb both light and O₂. The ability of OS to manipulate O₂ may shed light on the pathogenesis of many retinal degenerative diseases ascribed to oxidative stress, as well as on the efficacy of the treatment with dietary supplements, presently utilised as supporting therapies.

The role of lutein in eye-related disease

The lens and retina of the human eye are exposed constantly to light and oxygen. In situ phototransduction and oxidative phosphorylation within photoreceptors produces a high level of phototoxic and oxidative related stress. Within the eye, the carotenoids lutein and zeaxanthin are present in high concentrations in contrast to other human tissues. We discuss the role of lutein and zeaxanthin in ameliorating light and oxygen damage, and preventing age-related cellular and tissue deterioration in the eye. Epidemiologic research shows an inverse association between levels of lutein and zeaxanthin in eye tissues and age related degenerative diseases such as macular degeneration (AMD) and cataracts. We examine the role of these carotenoids as blockers of blue-light damage and quenchers of oxygen free radicals. This article provides a review of possible mechanisms of lutein action at a cellular and molecular level. Our review offers insight into current clinical trials and experimental animal studies involving lutein, and possible role of nutritional intervention in common ocular diseases that cause blindness.

Inhibitory effects of astaxanthin, β-cryptoxanthin, canthaxanthin, lutein, and zeaxanthin on cytochrome P450 enzyme activities

Astaxanthin, β-cryptoxanthin, canthaxanthin, lutein and zeaxanthin, the major xanthophylls, are widely used in food, medicine, and health care products. To date, no studies regarding the inhibitory effects of these xanthophylls on the nine CYPs isozymes have been reported. This study investigated the reversible and time-dependent inhibitory potentials of five xanthophylls on CYPs activities in vitro. The reversible inhibition results showed that the five compounds had only a weak inhibitory effect on the nine CYPs. Lutein did not inhibit the nine CYPs activities. Astaxanthin weakly inhibited CYP2C19, with an IC₅₀ of 16.2 μM; and β-cryptoxanthin weakly inhibited CYP2C8, with an IC₅₀ of 13.8 μM. In addition, canthaxanthin weakly inhibited CYP2C19 and CYP3A4/5, with IC₅₀ values of 10.9 and 13.9 μM, respectively. Zeaxanthin weakly inhibited CYP3A4/5, with an IC₅₀ of 15.5 μM. However, these IC₅₀ values were markedly greater than the Cmax values reported in humans. No significant IC₅₀ shift was observed in the time-dependent inhibition screening. Based on these observations, it is unlikely that these five xanthophylls from the diet or nutritional supplements alter the pharmacokinetics of drugs metabolized by CYPs. These findings provide some useful information for the safe use of these five xanthophylls in clinical practice.

Macular pigment optical density and its relationship with refractive status and foveal thickness in Chinese school-aged children

PURPOSE

To investigate macular pigment optical density (MPOD) and its relationship with refractive status and foveal thickness in Chinese school-aged children.

METHODS

Ninety-four healthy Chinese children, 6 to 12 years old, were recruited to the study. MPOD was measured with a heterochromatic flicker photometer (HFP), and foveal thickness, including both minimum and central foveal thicknesses (MFT and CFT, respectively), were measured by optical coherence tomography (OCT) with fast macular map scan. A noncontact tonometer was used to measure intraocular pressure (IOP) followed by determination of the refraction using an autorefractor after cycloplegia. Information on body mass index (BMI) was obtained. The correlation between MPOD values and foveal thickness, spherical equivalent (SE) refraction, IOP, BMI, sex, and age was statistically analyzed using SAS 8.2 statistical software.

RESULTS

The MPOD in examined school-aged children was 0.56 ± 0.25, without any significant difference between boys and girls (p = 0.12). MPOD showed no significant association with age, BMI, IOP, SE, MFT, or CFT. In the myopia group, however, there was an inverse relationship between MPOD and MFT (R =-0.66, p = 0.028) and a positive relationship between MPOD and CFT (R = 0.67, p = 0.025).

CONCLUSIONS

MPOD was inversely related to MFT and positively related to CFT in Chinese school-age children with low-to-moderate myopia. MPOD showed no significant association with age, BMI, IOP, SE or foveal thickness.

Determination of carotenoids, total phenolic content, and antioxidant activity of Arazá (Eugenia stipitata McVaugh), an Amazonian fruit

The fruit of Arazá (Eugenia stipitata McVaugh) native to the Colombian Amazon is considered a potentially economically valuable fruit for the Andean economy due to its novel and unique taste. The fruit has an intense yellow color, but its chemical composition and properties have not been well studied. Here we report the identification and quantitation of carotenoids in the ripe fruit using high performance liquid chromatography (HPLC) with photodiode array detector (PDA) and atmospheric pressure chemical ionization (APcI) mass spectrometry (MS/MS). The qualitative carotenoid profile of the fruit according to maturity stage was also observed. Furthermore, antioxidant activity of the peel and pulp were assessed using the ferric reducing ability of plasma (FRAP), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) methods, in addition to chemical indexes and total phenolic content. Multiple carotenoids were identified in the peel and pulp including four xanthophylls (free and esterified as their mono and diesters) and two carotenes. One of the xanthophylls was tentatively identified as zeinoxanthin, while the others were identified as lutein, zeaxanthin, and β-cryptoxanthin. Carotenes included α-carotene and β-carotene. The total carotenoid content was significantly higher in the peel (2484 ± 421 μg/100 g FW) than in the pulp (806 ± 348 μg/100 g FW) with lutein, β-cryptoxanthin, and zeinoxanthin as the major carotenoid components. The unique carotenoid composition of this fruit can differentiate it from other carotenoid-rich fruits and perhaps be useful in authentication procedures. Overall, results from this study suggest that Colombian Arazá may be a good edible source of carotenoids important in retinal health as well as carotenoids with provitamin A activity. Therefore, Arazá fruit can be used as a nutraceutical ingredient and in production of functional foods in the Colombian diet.

Microalgae as sources of carotenoids

Marine microalgae constitute a natural source of a variety of drugs for pharmaceutical, food and cosmetic applications-which encompass carotenoids, among others. A growing body of experimental evidence has confirmed that these compounds can play important roles in prevention (and even treatment) of human diseases and health conditions, e.g., cancer, cardiovascular problems, atherosclerosis, rheumatoid arthritis, muscular dystrophy, cataracts and some neurological disorders. The underlying features that may account for such favorable biological activities are their intrinsic antioxidant, anti-inflammatory and antitumoral features. In this invited review, the most important issues regarding synthesis of carotenoids by microalgae are described and discussed-from both physiological and processing points of view. Current gaps of knowledge, as well as technological opportunities in the near future relating to this growing field of interest, are also put forward in a critical manner.

Temperature dependence of resonance Raman spectra of carotenoids

To understand the mechanism of the photoprotective and antioxidative functions of carotenoids, it is essential to have a profound knowledge of their excited electronic and vibronic states. In the present study we investigate the most powerful antioxidants: β-carotene and lutein by means of resonance Raman spectroscopy. The aim was to study in detail their Raman spectra in solution at room temperature and their changes as a function of temperature. To measure the spectra in their natural environment pyridine has been used as a solvent. It has been chosen because of its polarizability (n=1.5092) which is close to that of membrane lipids and proteins. The temperature dependence of the most intensive ν(1) band in the range from 77 K to 295 K at 514.5 nm excitation has been obtained. It was found that in pyridine the CC stretching frequency, its intensity, line shape, and line width are very sensitive to the temperature (the sensitivity being different for the two studied carotenoids). The observed linear temperature dependence of the CC stretching frequency is explained by a mechanism involving changes of the vibronic coupling and the extent of π-electron delocalization. The different behavior of the temperature-induced broadening of the ν(1) band and its intensity for the two studied carotenoids can be associated with the different nature of their solid matrices: glassy for β-carotene and crystalline-like for lutein, owing to their different chemical structures.

Post-translational protein modification by carotenoid cleavage products

Carotenoids are known to generate various aldehydes, known as carotenoid-derived aldehydes (CDAs), which could efficiently react with protein or DNA. In this in vitro model study, interaction between CDA and protein has been studied. Various proteins were incubated with CDA, and protein modification and adduct formation were confirmed by using matrix-assisted laser desorption and ionization time-of-flight, amino acid analysis, and measuring enzyme activity on modification with CDA. Using radiolabeled NaB((3) H)H(4) and Raney nickel as well as sulfhydryl assay (Ellman's reagent), we confirmed that CDA could conjugate with cysteine through a thioether linkage. The carbonyl assay using 2,4-dinitrophenylhydrazine revealed the possible involvement of Schiff's base reaction between CDA and lysine. The adducts formed between β-apo-8-carotenal (BA8C) and N-acetylcysteine and BA8C and N-acetyllysine were confirmed by HPLC and ESI-MS. Our results suggest that CDA could alter protein function by post-translational interaction with cysteine and lysine by thioether linkage and by schiff's based bonds, respectively. Thus, the formation of CDA adducts with proteins could alter functional properties of proteins responsible for maintaining cell homeostasis and thereby cause cellular toxicity. In view of these observations, further studies are required to understand the delicate balance between beneficial and/or harmful effects of carotenoids as a dietary supplement to slow age-related macular degeneration progression.

Innovative natural functional ingredients from microalgae

Nowadays, a wide variety of compounds such as polyphenols, polyunsaturated fatty acids (PUFA), or phytosterols obtained, for example, from wine, fish byproducts, or plants are employed to prepare new functional foods. However, unexplored natural sources of bioactive ingredients are gaining much attention since they can lead to the discovery of new compounds or bioactivities. Microalgae have been proposed as an interesting, almost unlimited, natural source in the search for novel natural functional ingredients, and several works have shown the possibility to find bioactive compounds in these organisms. Some advantages can be associated with the study of microalgae such as their huge diversity, the possibility of being used as natural reactors at controlled conditions, and their ability to produce active secondary metabolites to defend themselves from adverse or extreme conditions. In this contribution, an exhaustive revision is presented involving the research for innovative functional food ingredients from microalgae. The most interesting results in this promising field are discussed including new species composition and bioactivity and new processing and extraction methods. Moreover, the future research trends are critically commented.