Dr Anja Dahten and Dr Joerg Gruenwald

There is an increasing demand for effective antiaging ingredients with high activities at low dosages for sophisticated cosmeceutical products. As, worldwide, herbal ingredients are preferred, compared with chemical ones, the natural-organic market is still growing, and new “bioactive” ingredients have high market values. At the same time, consumers are increasingly asking for product quality and scientifically substantiated efficacy. To this end, the new health claim regulation, as well as the expected tightening of cosmetic laws, will force the majority of manufacturers to invest more time and money into scientifically proven product efficacy. But how do we validate the subjective impression of efficacy with objective measurements?

Scientific Background

Our skin is constantly exposed to pro-oxidant environmental stress resulting from air pollution, UV-radiation, chemicals, micro-organisms and ozone. Free radicals destroy collagen and elastin fibres, skin cell lipids, proteins and even DNA structures. In addition, an unhealthy lifestyle based on an unbalanced diet, alcohol consumption and smoking contributes to the assault on skin health and appearance by lowering its natural antioxidant defences, allowing oxidation processes to occur more rapidly. The consequences are the typical signs of aging, such as dry skin, hyperpigmentation, loss of elasticity and the increasing appearance of wrinkles and furrows. Therefore, the main purpose of antiaging products containing botanical ingredients is to increase the antioxidative potential of the skin. In recent years, a broad range of antioxidants, such as vitamins, carotenoids, polyphenols, minerals and fatty acids, have gained considerable attention in research. Typical antioxidants in the skin are vitamins A, D and E, enzymes and carotenoids. Several studies indicate that the antioxidant potential of the skin might be increased by the use of miscellaneous antioxidants in topical, as well as ingestible, formulations.

In general, the quality of botanicals and food ingredients varies with the respective method of extraction and manufacturing procedure. The first step in cosmeceutical development should be choosing the most favourable ingredient formulation regarding its optimal bioavailability. The classic route of topical application to the skin offers the benefit of a targeted, local treatment. But an active substance administered to the skin must penetrate the epidermis in sufficient amounts to have a measurable effect, limited by molecule dimensions, solubility and chemical interactions. Apart from its penetration properties, topically applied substances often have low stability. By contrast, orally ingested bioactives are potentially metabolized and presented to the entire tissue in their active forms. Furthermore, blood may continuously replenish skin components such as the epidermis, dermis, subcutaneous fat and sebum. But to reach the bloodstream and circulation, active substances have to pass through the gastrointestinal tract and the intestinal barrier. This step could be a limiting factor for the efficacy of orally applied bioactive compounds.

Studies regarding the skin bioavailability of dietary compounds are still rare. Moreover, some nutrients (minerals such as selenium, zinc or copper, for example) indirectly affect skin properties via enzymatic secondary messenger pathways. By promoting enzymatic scavengers, they provide a greater range of skin damage protection compared with a single compound. By contrast, antioxidants such as beta-carotene or vitamins C and E have been shown to directly neutralize free radicals. Therefore, we have to recognize that, aside from analysing the particular ingredients used, the final formulation and mixture–at least–must be tested for true product efficacy. But claims are often based solely on the individual ingredient data and/or traditional use. Furthermore, in vitro data can provide the first indication of ingredient actions, but only placebo-controlled, clinical trials are able to substantiate a proposed health benefit. In an attempt to evaluate the efficacy of useful ingredients and products, we conducted a critical examination of the manufacturers’ clinical data, based on our experience with clinical trial development regarding cosmeceuticals, supplements and functional food.

Antioxidant Efficacy

Carotenoids such as beta-carotene and lycopene are the most important antioxidants for the skin. They have been shown to be highly effective quenchers of free radicals in vitro. Furthermore, subsequent studies have demonstrated that dietary carotenoids measurably accumulate in skin. Carotenoids are the most widely researched bioactives, offering photoprotective benefits via absorption, reflection and/or the scattering of visible and UV light. Clinical studies on the systemic use of beta-carotene have shown that a daily intake (15-30 mg), during a period of about 7-12 weeks, increases protective skin properties against UV-induced erythema and inflammations. A recent study of women (aged 25-50) showed that a daily intake of 10 mg of lutein for 12 weeks significantly increased skin hydration and elasticity. Now, new spectroscopic data from the Dermatological Department of Prof. Lademann at the Charite University (Berlin) indicates that higher levels of cutaneous carotene concentrations are correlated with measurably lower levels of skin roughness, reflected by fewer furrows and wrinkles. In this case, lycopene seems to be more efficient than beta-carotene. To increase their antioxidant potential, carotenoids are often combined with vitamins C and E. Nestle has formulated a new dietary supplement under the Glowelle brand containing a proprietary blend of vitamins (A, C and E) and 5 g of lycopene. To better substantiate such antioxidant-mediated effects in topicals and nutricosmetics, the working group of the UV-expert, H. Piazena, under the leadership of Prof. Dr R. Uebelhack (Charite), is now focusing on innovative new measurements to characterize skin physiology.

Plant extracts from green tea, mate, cocoa, berries, grape seed and Aloe vera have traditionally been used as topical applications for wound healing and in antiaging treatments. These plants share one characteristic feature: they all produce flavonoid compounds with phenolic structures, which are highly potent agents for neutralizing free radicals. It is often difficult to evaluate the specific effects of a given compound, because a large number of antioxidants occur in plants and plant extracts. But, it seems that even these mixtures give the desired results. Polyphenols are mostly present in blood, and their exact mechanisms of action still remain unknown; but, in vitro data give useful indications of nutrients with potentially multifunctional applications, including antioxidant, UV-protective and anti-inflammatory properties.

Peptides are short-chain proteins that naturally occur in the skin and mainly act as messengers (signalling peptides) or hormones. They have been the subject of some 50 years of research, and are among the most popular functional ingredients used in topical skincare products. Furthermore, they have been shown to play a key role in natural skin healing processes. Products containing peptides claim to affect the skin with smoothing and nourishing effects. Peptides and their degradation products are key players in the fields of cosmetics and dermatology. Constantly developing technologies enable us to purify and develop toxicologically safe peptides with high specific mechanisms and local effects. Snowberry NZ has incorporated several biopeptides in the face and eye sera of its new antiaging skincare product line, which promises to restore and increase the elasticity of skin. Clinical trials have already demonstrated a remarkable reduction in wrinkle number (15%) and length (25%), as well as a moisturizing effect of about 50%. Currently, Snowberry is conducting an additional double-blind clinical trial at the Dermatological Department of Charite University.

But, as some data also suggest an antiaging potential for orally applied proteins and peptides, oral collagen application is receiving increasing attention on the international beauty food market. Scientific research into intestinal absorption and accumulation (cartilage) points to effective delivery by oral ingestion. Furthermore, it was shown that the daily ingestion of 10 g of collagen-peptide beneficially affects adult women’s skin. Properties such as water absorption and hydration, and an increased density of collagen fibrils, were observed in animal studies. However, further investigations including clinical trials are necessary to confirm this notion. Rousselot has been performing intensive research to develop a food supplement for the cosmeceutical market. The hydrolysed type I collagen, Peptan, contains 20 amino acids and can be included in cosmetics as well as beauty foods and beverages. The product is claimed to rejuvenate and redensify the skin through a daily intake of 5-10 g during a period of 30-60 days.

Another trend is the increasing consumer interest in ethnic and traditionally used plants. The scientific literature refers to hundreds of interesting African plants that are used to treat wounds, burns and skin conditions. Because of their anti-inflammatory, antibacterial, antiviral as well as moisturizing and tightening properties, fruit pulps and oils from plants such as Baobab, Kigelia and Ximenia have great potential for the cosmeceutical market. In particular, Kigelia fruit extracts are becoming more and more popular in organic face creams and body lotions. A variety of well-characterized new African fruits is becoming available through PhytoTrade Africa (www.phytotrade.com). In the near future, we expect more innovative organic skincare products to incorporate these promising plant extracts.

Conclusion

Antiaging effects on skin health will always remain one of the most important issues for the beauty market. Intensive research into the long-term effects and control mechanisms of aging skin is ongoing and will continue. We can conclude that no single emollient will make the perfect moisturizer for all skin types, nor will any single antioxidant neutralize all free radicals or any single peptide perform all the functions in a cell and/or intercellular matrix. As both topically and orally applied dietary ingredients may improve skin health by various mechanisms and in different intensities, the most efficient way to fully exploit the natural potential of these ingredients is to combine cosmetic and nutricosmetic benefits. However, it must be further clarified how they act in efficient combinations beyond in vitro or ex vivo data, dependent on the ingredient concentration and modification–as well as on the product formulation itself–by well-documented placebo-controlled clinical trials.