Natural products analysis carotenoids

MALDI-TOF-MS facilitates the analysis of carotenoids and other natural products with detection limits that are lower than most other techniques. For example, subpicomole quantities can be detected (Wingerath et al., 1999). The enhanced sensitivity is the result of the efficiency of the pulsed ionization and detection system in which a complete mass spectrum is recorded with each laser flash. Like FAB and LSIMS, molecular ions are the most abundant sample ions, although some protonated molecules and [M-H]+ ions may be formed as well. Abundant molecular ions of carotenoid esters have been observed using MALDI-TOF-MS (Kaufmann et al., 1996 Wingerath et al., 1996),... 

Additional noteworthy applications of CEC include natural products such as the plant flavonoids hesperetin and hesperidin [160], anthraquinones extracted from rhubarb and from Chinese medicine [161], and heterocyclic compounds present in oils of bergamot, mandarin, and sweet orange [162], The CEC analysis of retinyl esters has been investigated by Roed et al. in nonaqueous mode for the separation of liver extracts of arctic seal [163]. Carotenoid isomers were also separated on C30 stationary phases by nonaqueous CEC [164]. It was found that CEC offered increased resolution compared to HPLC, and in CEC... 

The first comprehensive 2D system was developed in the late 1970s by Erni and Frei, who applied IEX x RPC to the analysis of senna glycosides from plant extracts.61 In the subsequent decades, comprehensive MD-HPLC methods have been further developed, mainly for peptides and proteins,62 3 but also for separation of various natural products such as phenolic and flavone antioxidants64 and carotenoids.65 The theoretical aspects of MD-HPLC techniques have also been further developed.66-68... 

The classic sequence of experiments with natural compounds in the twentieth century has been as follows isolation from biological sources, purification, elucidation of molecular structure, and finally total synthesis. These tasks of organic chemistry were fulfilled by the end of the century as far as the major components of higher organisms are concerned. Only compounds that are central to the growth of their tissues are the subject of this book. Many individual compounds of this kind of natural product, namely lipids, steroids, carbohydrates, carotenoids, porphyrins, vitamins, nucleic acids, and proteins, are today commercially available, and their structural and dynamic analysis has reached an accuracy and diversity that leaves little to be desired (Karrer, 1954 Fieser and Feiser, 1960 Tedder et al., 1972 Nuhn, 1981 Fuhrhop, 1982 Beyer and Walter 1988 Fuhrhop and Penzlin, 1994 Mann et al., 1994). 

This chapter presents method of extraction/isolation and analysis of carotenoids in natural products. General procedures of solvent extraction/isolation and analysis of carotenoids are described. Preparation and determination of carotenoids are also explained. ... 

Note An internal standard is a compound that is not present in the sample, but is chemically and physically similar to the analytes of interest. A fixed quantity is incorporated into the calibration solutions. The same concentration of internal standard is added to the samples during extraction to compensate for analyte recovery and injection variability. As seen in Fig. 111.5, Echinenone, which is not typically found in natural products, is used as the internal standard. Unfortunately, compounds which may be used as internal standards for carotenoid analysis are not readily available commercially. 

Fig. 111.7 Gradient HPLC analysis of the natural products reference matruial carotenoids using procedure 4.2.3. Conditions 3- jm x 250-nun x 4.6-mm waters C30 column, 1.0 ml/min flow rate, visible detection at 450 mn, column temperature 35°C, solvent A = 50 mM ammmiium acetate in methanol, B = isopropyl alcohol, and C = THF (all solvent contain 0.1% TEA). Flow program 90% A/10% B linear gradient, 54% A/35% B/11% Cover 24 min, linear gradient to 30% A/35% B/35% C over 11 min, hold for 8 min, and then return to initial conditions over 10 min [84]...

The high sensitivity and selectivity of mass spectrometry (MS) facilitates the identification and structural analysis of small quantities of carotenoids that are typically obtained from natural product samples such as plants, animals, or human serum and tissue. Structural information from the abundant fragmentation is provided by classical ionization methods, such as electron impact (El see Sect. 4.3.1) and chemical ionization (Cl see Sect. 4.3.1), but molecular ions are not always observed. Recent advances in soft ionization techniques, such as fast... 

Fig. 111.8 Isocratic HPLC analysis of the natural products reference material carotenoids using procedure4.2.4. Conditions Lichosorb Si60,5-pm x 250-mm x 4.6-mm column, hexane/dioxane/ IPAATEA (80 20 0.15 0.02) mobile phase, 1.0 ml/min flow rate, and visible detector at 450 nm [84]...

Analysis carotenoids health benefits natural pigments plant biosynthesis production... 

Insights into the mechanisms of carotenoid degradation can be followed in model systems that are more easily controlled than foods and the formation of initial, intermediate, and final products can also be more easily monitored. However, extrapolation to foods must be done with caution because simple model systems may not reflect the nature and complexity of a multicomponent food matrix and the interactions that can occur. In addition, even in model systems, one must keep in mind that carotenoid analysis and identification are not easy tasks. 

The discussion above has addressed the assessment of a product s colour or perceived colour in basic terms. In the next two sections, methods to determine which coloured compounds are present in a product will be addressed. For the purpose of this chapter, the section on synthetic dyes will cover the analysis of the water-soluble dyes, or so-called coal tar dyes, and the section on natural pigments will cover the anthocyanin pigments, such as grape skin extracts, and the carotenoid-based materials, even if they are of synthetic origin. 

Separation and Assay. Procedures for the separation, purification, and assay of carotenoids and retinoids by h.p.l.c., g.c., and g.c.-m.s. are given in an extensive article." Another, general, review includes information on the h.p.l.c. separation of retinoids.A particularly useful method has been developed for resolution and analysis of some carotenoid optical isomers.For example, (3R,3 R)-, (3S,3 S)-, and (3/ ,3 5)-astaxanthin were converted into the diastereomeric (-)-camphanic acid diesters, which were separated by h.p.l.c. This procedure has been used to analyse the isomeric composition of a natural astaxanthin sample. An h.p.l.c. procedure for separation of a-, P-, and y-carotenes (173)—(175) and lycopene (176) has been described." Several papers describe methods for the h.p.l.c. separation and purification of various retinal and retinol isomers and derivatives.A procedure for the preparative t.l.c. of oxidation products of retinyl acetate has been described,and a competitive protein-binding radioassay for retinoic has been reported. 

ATR-IR spectroscopy was used for in situ analysis of naturally occurring carotenoids in tomato fruits and tomato products [5]. Most important pigments of red tomato fruits are lycopene and /i-carotene, which are 11- and 9-conjugated carotenes, respectively. 

D. (1973) Vibrational spectra of some carotenoids and related linear polyenes - Raman spectroscopic study. /. Am. Chem. Soc., 95 (14), 4493-4501. Schulz, H., Baranska, M, and Baranski, R. (2005) Potential of NIR-FT-Raman spectroscopy in natural carotenoid analysis. Biopolymers, 77 (4), 212-221. Baranska, M., Schutze, W, and Schulz, H. (2006) Determination of lycopene and /J-carotene content in tomato fruits and related products Comparison of FT-Raman, ATR-IR, and NIR spectroscopy. Anal Chem., 78 (24), 8456-8461. 

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