Natural sunscreen: Blooming algae protect sunbathers
- Published: Feb 1, 2017
- Author: David Bradley
- Channels: UV/Vis Spectroscopy
Ultraviolet screening agents derived from algal natural products that protect the marine microbes from the sun can boost the sun protection factor of skin creams used by sunbathers by a factor of more than two according to Spanish researchers.
When venturing out in the sun, you might take Baz Luhrmann's advice from his 1999 hit music/poetry hit "Everybody's Free (To Wear Sunscreen)" or better still take to heart the antipodean plea to "Slip! Slop! Slap!" Either way, outdoor types in sunnier climes and sunworshippers wherever they seek to sunbathe might well assume that sunscreen is screening them from the sun. Unfortunately, sun protection is never as simple as the application of cream to one's skin. Indeed, there are several expert organisations that suggest any sun exposure is a risk factor for skin cancer and that dietary intake of vitamin D trumps the production of that essential substance in the skin under the action of ultraviolet light from the sun.
Skin cancer incidence has been increasing in recent years with melanoma being the most lethal and responsible for more than 22000 deaths in Europe and 76 000 cases in the USA in 2016. Partly to blame is depletion of the protective ozone layer way above our heads. But, also perhaps the increased availability of inexpensive air travel and a propensity of many of us with fair skins to spend time on sunny beaches and swimming as a means to escape the daily grind. Sunscreens commonly contain substances designed to minimize the solar light transmission in the ultraviolet A (315 to 400 nm) and B (280 to 315 nm) regions. These compounds can delay the onset of solar erythaema, more familiar to us as sunburn. However, they have low photostability and ultimately do not protect the underlying biomolecules, and in particular, DNA, from ultraviolet photochemical damage. Moreover, there are safety concerns about many of these compounds, such as their ability to traverse the skin and enter the body. Many are known as endocrine disrupting chemicals.
According to researchers from Spain writing in Angewandte Chemie, "The ideal sunscreen should block UVB and UVA radiation while being safe and stable." Now, Raúl Losantos, Ignacio Funes-Ardoiz, Cristina García-Iriepa, Pedro Campos, and Diego Sampedro of the Universidad de La Rioja in Logroño and José Aguilera and Enrique Herrera-Ceballos of the Universidad de Málaga, have now developed an entirely new family of UVA and UVB filtering compounds based on natural sunscreen substances found in algae and cyanobacteria. The team says that these compounds are highly stable and enhance the effectiveness of commercially available sunscreens.
The natural sunscreen molecules detecting by a different type of screening are called microsporine-like amino acids (MAAs) and are widespread in the microbial world, most prominently in marine algae and cyanobacteria. MAAs are small molecules derived from amino acids, thermally stable, and they absorb light in the ultraviolet region, protecting the microbial DNA from radiation damage. Thus, the team points out, these compounds are natural sunscreens. Sampedro and his colleagues have now synthesised and tested easier to make derivatives of these sunscreen compounds and found them to be effective.
The team's theoretical calculations revealed what was chemically needed for a successful design. "We performed a computer calculation of several basic scaffolds to identify the simplest compound that fulfils the prerequisites for efficient sunscreens", Sampedro and colleagues say. The result of their search was a set of molecules which were readily synthesized, "avoiding the decorating substituents that come from the biosynthetic route." Thus the small basic molecules can be tuned to give them more favourable properties.
In their tests, the team demonstrated that their synthetic analogues of the algal sunscreen are highly effective at filtering the pertinent UV range. In addition they are photostable, much more than, for example, oxybenzene which is a widely used sunscreen in commercial formulations. The team also showed that these compounds do not react chemically and dissipate radiation thermally. When added alongside commercial sun protection agents, these natural sunscreens boosted the sun protection factor (SPF) by a factor of more than two.
Angew Chem Int Edn Engl 2017, online: "Rational Design and Synthesis of Efficient Sunscreens To Boost the Solar Protection Factor"
Article by David Bradley
The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.
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