University of KwaZulu-Natal – MSc
For thousands of years, humans have protected themselves from the sun. The ancient Egyptians, for example, were known for their advanced knowledge of skincare and sun protection. Prehistoric scrolls record how they used aloe vera, clay and a variety of natural oils from flowers, fruits, seeds and nuts to create sunscreens. Ancient Greeks applied olive oil to their skin for the same purpose, while European women wrapped head-cloths in folds around their necks to protect themselves from solar radiation.
They knew what science has now proven: overexposure to sunshine, particularly the harmful ultraviolet (UV) radiation it contains, changes a person’s skin, and in the worst-case scenario leads to skin cancer. Sun-shielding ingredients are now added to many cosmetic products, from foundations and daily moisturising creams, to lipsticks. But a major issue with some sunscreens is that the more they are exposed to sunlight, the less effective they become.
According to the Cancer Association of South Africa (CANSA), South Africa has the second highest incidence of skin cancer in the world after Australia. Sunscreen is one way to reduce the risk of getting skin cancer, but not all sunscreens are made equal. Commercial sunscreens contain UV filter substances that were originally designed to protect human skin from getting sunburnt, clinically known as erythema (reddening of the skin). These UV filters include chemical absorbers (such as the yellow powder avobenzone) that absorb UV radiation before it reaches the skin or physical blockers (like titanium dioxide, which is also widely used as a whitening pigment). These filters reflect, scatter or absorb the sun’s radiation. The less radiation that gets through the sunscreen, the better protected your skin.
A major problem for the cosmetic industry is the stability of these chemical absorbers. Some chemical absorbers degrade when they are exposed to UV radiation, which allows adverse reactions to occur. Also, UV filters only provide protection from a small range of light and others break down over time into either harmless chemical compounds or into toxic chemicals. The toxic ones can then cause phototoxicity or photoallergic reactions. Phototoxic reactions occur when excessive UV energy is absorbed by the sunscreen’s UV filters. This absorbed energy can cause molecular changes to the skin, which may lead to longterm damage to the skin and kills skin cells. Photoallergic reactions happen when UV rays cause the molecule to change into a different chemical compound. Our immune system then attacks the foreign compounds in a typical allergic reaction. Either way, both situations mean that these sunscreens will be less effective in protecting you from the sun because the sunscreen has “lost” some of its sun protection factor (SPF).
My current research involves adding natural plant extracts to improve the efficacy of sunscreens. I’m hoping to increase the time period that the sunscreen will be effective when exposed to sunlight, so that people will not have to reapply sunscreen – something which most people forget to do. But it is also important that these additives do not cause physical or environmental harm.
Plants naturally protect themselves from solar radiation. Although they use sunlight for photosynthesis, they can’t avoid exposure to enhanced levels of UV radiation, and have developed some crafty protection strategies. For example, their first layer of “skin” provides protection and an initial barrier against solar radiation. This layer, known as the epidermis, is covered in hairs that contain UV-absorbing compounds. These hairs interrupt the passage of UV light before it reaches the plant’s surface. Instead, they channel the light into water found in the middle of the hair, where it is absorbed, thereby protecting the plant. Importantly, plants also produce high levels of antioxidants; antioxidants inhibit the production of free radicals inside the plant. Free radicals begin a chemical cascade (a continuous series of chemical reactions), which ultimately damages an organism’s cells. Antioxidants, such as vitamin C, have the ability to stop these reactions. Determining how these antioxidants work in plants and in their extracts, is the future of skin-cancer and erythema prevention.
The plant kingdom offers a cornucopia of substances that could be safer sunscreen ingredients. In particular, bitter aloe (Aloe ferox) and rooibos (Aspalathus linearis) are emerging as possible contenders. Many studies have confirmed that extracts of these indigenous plants are able to prevent the creation of cancer cells and are non-toxic. Historically, traditional healers in South Africa used bitter aloe to treat dermatitis, acne, and skin diseases such as skin cancer. A gel obtained from its leaves is already used in various cosmetic products such as moisturisers. The aloe gel offers protection against wrinkling, and promotes skin regeneration, because it restores the activity of skin cells whose normal function has been impaired by exposure to UV radiation. This makes bitter aloe a good candidate for sunscreen formulations.
Green rooibos extracts, which contain polyphenols, are very popular in Africa because the plant is abundant and affordable. Polyphenols are a class of chemical compounds found in plants that are potent antioxidants and which provide protection against skin changes such as aging, blemishes and pigmentation. Free radicals are the main cause of these forms of skin damage but the antioxidants found in plants can inhibit or slow down the process of free radical formation. As a result, they prevent premature aging. This process can also repair damaged skin cells and promote new skin cell regeneration. Many skincare products, such as shower gels, toothpastes, shampoos and perfumes, already make use of these extracts.
Because these extracts have strong UV-absorbing properties, we assume that they can provide protection over a broad spectrum. And we’ve assumed that they can add this level of protection if they’re added to sunscreens. But this hasn’t been proven yet, and is currently being investigated in my research.
However, we still need to do a great deal of research before we can put these ingredients into sunscreens.
Also, not all plants are appropriate for sunscreens. St John’s Wort, for example, has been used for centuries as a herbal supplement to treat depression. But when sunscreen researchers combined an extract from this bushy shrub with its bright yellow flowers with sunscreen, they found that it actually made people’s skin more sensitive to sunlight. Therefore, the choice of plant for use in sunscreens is crucial.
The use of plant extracts is not the only way to deal with detrimental UV radiation, but plants can supplement existing strategies. Plus there’s a potential economic benefit to our research: if we can develop local products from natural resources, we could stimulate the country’s economy through increased revenue and employment – and we’ll rely less on imported products and materials.