Melanin, fractionation

Hayes et al. reported that in 200 samples of hair, the average value of THC-carboxylic acid was 4 pg/10 mg hair digest. This concentration appeared to be substantially less than the average value of 6 pg/10 mg of hair when the melanin fraction was examined. 

Note Numbers are in units of ng cocaine/10 mg hair. The hair was exposed to 2.5 pg/mL of cocaine containing tracer for 1 h, rinsed two times with distilled water, and dried. After centrifugation, all the digested hair in the supernatant could not be separated from the melanin pellet. Therefore, some residual amount of the drug remained associated with the melaiun pellet. This amount is estimated to be between 2 to 10% of the total. Thus, the amount of cocaine actually associated with the melanin fraction is even less than that cited above. 

Macro affinity, 160 Magnus, Rudolph, 34 Materia Medica, 147 Mathematical models, 42-43 Maximal fractional inhibition, 65 Maximal response of agonists, 85, 98 Medicinal chemistry, 1-2 Melanin, 50 Melanophores... 

The following example describes the results of the dereplication of an HTP fraction library for inhibition of melanin formation in an in vitro assay with a B16 cell line [54]. Briefly, following the inhibition and cell viability assay, the active organic extract from the whole plant of Mallotus repandus was fractionated with HTP. All of the HTP fractions were tested for melanin inhibitory activities. As shown in Figure 8, there are three major peaks exhibiting > 50% inhibitions of melanin synthesis and seven minor peaks exhibiting weaker inhibitions. The sharp activity peaks indicate the quality of the separations, which distributed the active components in three to five cells. 

Fig. (8). The melanin production inhibition and cell toxicity of HTP fractions from Mallotus repandus.

Since the melanin formation assay was run against a cell viability assay, the activity peak maximum at fraction Dll was most likely due to cytotoxicity. The dereplication of another active peak located from fractions D7 to D2 is illustrated in Figure 9. Every active fraction was analyzed by HPLC/PDA/MS. There was a peak located at Rt=16.33 min in the LC/MS total ion chromatogram of active fractions. This peak showed the same pattern of increasing to decreasing intensity as the trend exhibited by the melanin inhibition activities of those fractions. 

Dopa, dopamine, and tyrosine have been the most common substrates in the preparation of synthetic eumelanins. In a typical experiment the enzyme (15 ml of solution of 30 mg of enzyme in 100 ml Sorensen s buffer, pH 7) and L-dopa (150 mg) in pH 7 buffer (500 ml) are kept with access to air for 2 weeks (755) stirring, bubbling air through the mixture, and raising the temperature up to 38°C accelerate the process. Melanin is separated by filtration, fractional sedimentation, or, more efficiently, by centrifuging (500 to 100,000 g), especially after acidification (pH < 3.5) (see Section IV) (251). Samples are further purified by repeated resuspension and centrifugation or dialysis (252). 

Gel permeation chromatography has been used in studies of water-soluble melanins. Several fractions were separated from allomelanin from Aspergillus niger on Sephadex G gels (Ref. 7, p. 131). Similarly, humic acids were separated into three fractions on Sephadex G-75 (297). 

The chemical compositions of melanosoma and mitochondria have been determined and compared, using differential and density-gradient techniques 241). The data show that melanosomal fractions contain a high percentage of Zn and a low content of RNA and phospholipid-P as compared with mitochondrial fractions. The lack of succinoxidase and glutamate oxidase activities support the idea that melauosomes are sub-cellular particles, different from mitochondria, and contain a particular specialized metabolic pathway through which tyrosine or dopa is converted into melanin (259). 

Lasers, light therapy, and fractional resurfacing aim to disrupt melanin granules and thus decrease the degree of pigmentation. 

The fate of radiation incident upon the skin is determined by the optical properties of the tissue. Two basic interactions with photons occur - scattering and absorption. When radiation strikes the skin, part is scattered back to the environment, part is absorbed in various layers, and part is transmitted inward until the energy has been dissipated. At the surface of the stratum corneum a fraction of about 5-7% of the incident radiation is scattered backward (reflected), since the refractive index of the stratum corneum (nsc l-55) is much higher than that of air (n = 1.00). In the epidermis, aromatic amino acids (both free and in protein, wavelength of absorption maximum Xmax near 275 nm), urocanoic acid (X av near 277 nm at pH 7.4), nucleic acids (X ax near 260 nm), and melanin (broad absorption... 

Chemical Descriptions A nanoparticulate suspension that imparts a natural color to formulae, hair, and skin. Melanin is compo.sed of four major monomeric units uncyclized units indoles indolines and pyrroles, It has an empirical formula of C74.7S H45.62N Oi ..,. Both the fractional nature and range of the empirical fonnula reflect the fact that melanin is a polymer composed of various percentages of more than one type of monomeric unit Trade Names Melanlnk, SepiaMelanInk, All Natural Melanin Function in Formula Free-radical neutralization, adjuvant for boosting SPF Use Concentration 0.1-10% in skin care formulations 0.1-10% in hair care formulations... 

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