UV-sunscreen

The main commercial apphcations for sahcylate esters are as uv sunscreen agents and as flavor and fragrance agents. Several have apphcation as topical analgesics. A number of sahcylate esters of commercial interest and their physical properties are hsted in Table 8. 

Microwave activation and solvent-free PTC have been shown to be of prime efficiency for the synthesis of new benzylidene cineole derivatives (UV sunscreens) by the Knoevenagel reaction. When performed classically by use of KOH in ethanol at room temperature for 12 h (Eqs. 43 and 44) the yield was 30%. This was improved to 90-94% within 2-6 min under PTC + MW conditions (Tabs 5.17 and 5.18) [27, 28],... 

As mentioned in Sect. 13.3.6, carotenoids serve mainly as accessory pigments in the light harvesting complexes of the photosynthetic apparatus, and additionally as cellular protection against ROS. Whether carotenoids also act as passive UV-sunscreens is... 

Sporopollenin is a complex polymer made up of a diversity of aromatic and aliphatic residues, which occurs in many algal cell walls where it non-specifically attenuates UV radiation (Xiong et al. 1997). It may therefore act as a constitutive UV sunscreen compound. 

Garcia-Pichel F, Sherry ND, Castenholz RW (1992) Evidence for a UV-sunscreen role of the extracellular pigment scytonemin in the terrestrial cyanobacterium Chlorogloeopsis sp. Photochem Photobiol 56 17-23... 

F. Garcia-Pichel, C.E. Wingard, R.W. Castenholz (1993). Evidence regarding the UV-sunscreen role of a mycosporine-like compound in the cyanobacterium Gloeocapsa sp. Appl. Environ. Microb., 59,170-176. 

In vitro absorption-spectrophotometry techniques are available to assess a sunscreen s efficacy, but the preferred methods are in vivo procedures in which a small body site is irradiated with the desired wavelengths for different periods in the presence or absence of a uv protectant. Procedures vary from country to country to determine the incremental timing of the exposure that ultimately allows quantification via sun protective factor (SPE). In the United States, sunscreen preparations are considered OTC dmg products, and the SPE must be specified (54). Even in countries that do not identify these products as dmgs, SPE labeling has become customary. 

A hst of uv absorbing substances found useful in protective sunscreen products is provided in Table 13. Some information on the levels permitted in products in both the United States and the EEC is included. Descriptions and specifications of sunscreens have been pubflshed (55). 

In principle, emulsified sunscreen products are similar to emollient skin-care products in which some of the emollient Hpids are replaced by uv absorbers. The formulation of an effective sunscreen product generally requites combination of a uvB and a uvA absorber if an SPF above about 12 is desired. Two or more of the sunscreens Hsted in Table 13 normally constitute about one-half of the nonvolatiles found in sunscreen lotions. The other half consists of an em ollient (solvent) and emulsifying and bodying agents. If water-resistant quaUties are desired, polymeric film formers, for example, acrylates—octylacrylamide copolymers [9002-93-1] or water-repellent Hpids, for example, dimetbicone [9006-65-9] are included. 

More recendy anhydrous sunscreens have become popular. Products of this type are based on blends of em ollient lipids and acceptable uv absorbers. Formulations of sunscreen products have beenpubHshed (56). 

OXIDATIVE LUMINESCENCE OF UV ABSORBING CHEMICALS. APPLICATION TO THEIR DETERMINATION IN SUNSCREEN PRODUCTS BY REVERSED PHASE LIQUID CHROMATOGRAPHY WITH CHEMILUMINESCENCE... 

Notice from this equation that energy is inversely related to wavelength. This explains why you put on sunscreen to protect yourself from UV solar radiation (<400 nm) and a lead apron when dental x-rays (<10 nm) are being taken. Conversely, IR (>700 nm) and micro-wave photons (>80,000 nm) are of relatively low energy (but don t try walking on hot coals). 

PABA is taken orally in vitamin supplements. However, its widest use is as a sunscreen. Taking it orally will not protect a person from the sun as a sunscreen PABA acts as a topical dye that absorbs ultraviolet light. To block UV rays from the sun, a person needs to paint it directly onto the skin. 

Octyl methoxycinnamate (OMC) is the most common UV-B sunscreen that is on the market Eisenstadt, A. In Catalysis of Organic Reactions Herkes, F. E., Ed. Marcel Dekker New York, 1998 Chapter 33. 

How do Phytoplankton Cope with Enhanced UV Several investigators have reported the existence in Antarctic algae of UV-absorbing mycosporine amino acids identical to those of tropical and temperate marine species (37). These compounds absorb in the UV-B region of the spectrum and may act as sunscreens which may provide some measure of protection from damaging UV-B. 

Sun worshipers and those who work outside can protect themselves from ultraviolet exposure with skin creams that contain UV-absorbing molecules. The UV-absorbing molecule in the first sunscreens was PABA, para-aminobenzoic acid. However, this compound may have toxic effects of its own. The UV-absorbing components of current sunscreens are derivatives of cinnamic acid and benzophenone. 

Cover skin with a sunscreen lotion with a skin protection factor (SPF) of at least 15, protecting against UV radiation (both UVA and UVB). 

Sometimes for some very potent pollutants analytical methodologies provide limits of detection (LODs) higher than the concentrations that cause effects, as derived from ecotoxicological studies. Therefore efforts in the field of analytical chemistry (see Sect. 2) are focused on making available the necessary analytical capabilities to detect pollutants at the required low levels found in the environment. This was the case of pharmaceuticals, illicit drugs, perfluorinated compounds (PFCs), sunscreens/UV filters, etc. few years ago. However, this list is likely to increase with new family candidates. 

In this chapter, among the large variety of compounds, we include some of the emerging contaminants most commonly found in sewage sludge pharmaceutical compounds, estrogens, illicit drugs, UV filters (sunscreens), BFRs, and PFCs. 

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