Applications To Health Promotion And Disease Prevention

Characterization and free radical scavenging activity of novel red pigment from OFS

Natural colorants have attracted widespread interest because of their general health and safety benefits, and numerous other important properties. Therefore, the development of food colorants from natural sources is receiving increasing attention (Es-Safi, 2004). Recently, a natural red pigment of O. fragrans (RPOF) has been isolated from OFS in our laboratory (Pan et al., 2009). RPOF can be dissolved in alkaline or acidic water solutions, and common hydro-philic organic solvents. The color of a water solution of RPOF changes with pH (Table 59.1). RPOF is stable to heat in the temperature range 25—100°C. A study of the physical and chemical properties of RPOF reveals that the red pigment is also stable in the presence of Na2SO3, NaCl, amino acids, organic acids, sugars, starch, or metal ions (such as Ca2+, Cu

Mg , and Na+), but is bleached by strong oxidants (KMnO4, K2Cr2O7, and NaOCl).

Interestingly, RPOF shows excellent DPPH radical scavenging activity, and is superior to butylated hydroxytoluene (BHT). The scavenging effect is increased with increasing concentration and reaction times (Figure 59.1). RPOF also exhibits quite strong concentration-dependent inhibition of hydroxyl radicals at low concentrations, compared with ascorbic acid and quercetin. When the concentration of RPOF was 0.03 mg/ml, the scavenging percentage of hydroxyl radicals reached 92.3%.

Isolation, characterization, lipid peroxidation inhibition activities, total antioxidant activity, reducing power, metal chelating, and total phenolic compounds of natural melanin from OFS

Natural melanin from plants or animals possesses a broad spectrum of biological activities (Barr, 1983; Lukiewicz, 1972). Immunopharmacological properties of melanin are of great interest, because it may hold promise for AIDS treatment (Montefiori & Zhou, 1991). However, due to its rarity, natural melanin cannot be produced in sufficient amounts; thus, its application is restricted. In 2006, we reported that natural melanin from O. fragrans (NMOF) was isolated from OFS by alkaline extraction, acid hydrolysis, and repeated precipitation (Figure 59.2). The physical and chemical properties of NMOF revealed that the melanin obtained directly from OFS is similar to traditional melanin. NMOF is stable under ultraviolet light or room-light, stable in the range 25—100°C, and relatively stable in alkaline solution, reducer, and salt, but is bleached by strong oxidants (KMnO4, K2Cr2O7, and NaOCl). Metal ions, such as Ca2+, Cu2+, Fe3+, and Zn2+, will either increase the color or provide color preservation to NMOF solutions. Although Mg2+, Al3+, and Na+ reduce pigment color, it is not obvious. Amino acids and organic acids do not affect NMOF, while sugars, starch, and glucose slightly affect it (Wang et al., 2006).

The lipid peroxidation inhibition activities, total antioxidant activity, reducing power, metal chelating ability, and total phenolic compounds of NMOF have also been studied. The IC50 value for NMOF-inhibited lipid peroxidation is 0.135 mg/ml (Pan et al., 2005). The total

TABLE 59.1 Effect of pH and Solvent on Color and 1max of RPOF

Solvents or pH

Color

Imax (nm)

Water, pH 1

Sanguine

539.5

Water, pH 2

Red

539.5

Water, pH 3

Red

538.5

Water, pH 5

Red

538.5

Water, pH 7

Henna

538.5

Water, pH 10

Light henna

538.5

Water, pH 12

Green

535.5

Methanol

Red

528.0

Ethanol

Red

537.0

Acetone

Henna

524.0

Red pigment of Osmanthus fragrans seed (RPOF) was dissolved in water with different pH, different colors were assumed, and slight changes in the maximum absorption wavelengths (1max).

Reprinted from Pan et al. (2009), Food Chem.,112, 909—913, with permission.

Red pigment of Osmanthus fragrans seed (RPOF) was dissolved in water with different pH, different colors were assumed, and slight changes in the maximum absorption wavelengths (1max).

Reprinted from Pan et al. (2009), Food Chem.,112, 909—913, with permission.

20 30 40

Time (min)

FIGURE 59.1

DPPH free radical scavenging activities of RPOF and BHT. Red pigment of Osmanthus fragrans seeds (RPOF) possessed significant scavenging activity on the DPPH radical, and the scavenging effect increased with increasing concentration and reaction time. ■, 0.2mg/ml RPOF; o, 0.5 mg/ml RPOF; 6, 0.8mg/ml RPOF; 1.2 mg/ml RPOF; >, 0.5mg/ml BHT. SC % (percentage of scavenging activity of DPPH radical) = [1 - (absorbance of sample)/(absorbance of control)] x 100. Results are mean ± SD of three parallel measurements. Reprinted from Pan et al. (2009), Food Chem., 112, 909—913, with permission.

20 30 40

Time (min)

FIGURE 59.1

DPPH free radical scavenging activities of RPOF and BHT. Red pigment of Osmanthus fragrans seeds (RPOF) possessed significant scavenging activity on the DPPH radical, and the scavenging effect increased with increasing concentration and reaction time. ■, 0.2mg/ml RPOF; o, 0.5 mg/ml RPOF; 6, 0.8mg/ml RPOF; 1.2 mg/ml RPOF; >, 0.5mg/ml BHT. SC % (percentage of scavenging activity of DPPH radical) = [1 - (absorbance of sample)/(absorbance of control)] x 100. Results are mean ± SD of three parallel measurements. Reprinted from Pan et al. (2009), Food Chem., 112, 909—913, with permission.

FIGURE 59.2

Procedure for extraction of melanic pigment from OFS. Melanic pigment from Osmanthus fragrans seeds (OFS) was isolated by alkaline extraction, and could be purified by acid hydrolysis, organic solvent (chloroform, ethyl acetate, and ethanol) treatment, and repeated precipitation. Reprinted from Wang et al. (2006) LWT-Food Sci. Technol., 39, 496—502, with permission.

FIGURE 59.2

Procedure for extraction of melanic pigment from OFS. Melanic pigment from Osmanthus fragrans seeds (OFS) was isolated by alkaline extraction, and could be purified by acid hydrolysis, organic solvent (chloroform, ethyl acetate, and ethanol) treatment, and repeated precipitation. Reprinted from Wang et al. (2006) LWT-Food Sci. Technol., 39, 496—502, with permission.

antioxidant capacity of NMOF is 0.25 g ascorbic acid/g (Wang et al., 2004). NMOF shows higher antioxidant activity than BHT. Polyphenolic compounds have an important role in stabilizing lipid oxidation, and are associated with antioxidant activity (Yen et al., 1993). The total phenolic content of OFSM (1 mg) is 12.5 mg pyrocatechol equivalent (Pan et al., 2005). There is a correlation between antioxidant activity, reducing power, metal chelating ability, and total phenolic compounds. Similar to antioxidant activity, the reducing power and the metal chelating ability of NMOF depend on concentration, and increase with increasing concentration of NMOF.

In vitro sun protection factor of NMOF-bearing gel formulation

It is a well-known that over-exposure of human skin to ultraviolet light may lead to sunburn, premature skin aging, and an increased risk for skin cancers (Diffey et al., 2000). There has been increasing interest in the use of antioxidants in sunscreens to provide supplemental photoprotective activity. Antioxidants from natural sources may provide new possibilities for the treatment and prevention of UV-mediated diseases (Bonina et al., 1996; Saija et al., 1998).

Recently, we have determined the in vitro sun protection factor (SPF) of an NMOF-bearing gel formulation using the method of Sayre and colleagues (1979). Results from the sun protection factor (SPF) in vitro determination of melanin-bearing gel formulations indicate that the SPF value of every formulation increased with the amount of NMOF, suggesting the presence of additional compounds with sunscreen activity in NMOF.

Chemical composition of OFS

Salidroside was isolated as an active component with radical scavenging activity from RPOF (Pan et al., 2009).

Recently, we have isolated six compounds from OFS: oleanolic acid, b-sitosterol, stigmasterol, b-sitosterol-3-glucoside, (8E)-niizhenide, and secoiridoid glucoside GL3.

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