Some vegetable oils are currently being promoted as a safe alternative to commercial sunscreens. The true UVB photoprotective efficacy of 14 virgin vegetable oils and the suitability of the dilution method for determining their SPF value were evaluated. Oils and standard sunscreens were investigated in vitro by the Mansur's method in Slovakia and in vivo by the ISO method in the Czech Republic. SPF values in vitro (0.1; 0.0; 0.4; 0.2 and 0.2) and in vivo (2.5; 1.2; 2.6; 2.6; and 2.8) of the five most promoted oils (from carrot seed, coconut, raspberry seed, rosehip seed, and wheat germ) were significantly lower than the values reported in the controversial studies. We have shown that the overestimated SPF values of these oils were determined by authors who did not strictly follow Mansur's original methodology. The other eight vegetable oils also provide no or negligible SPF values. Only the in vitro SPF value of 11.2 tamanu oil is worth mentioning, probably due to high proportion of calophyllolides. In vitro and in vivo SPF ratios from 1.14 to 0.94 obtained by two methods in two laboratories for six commercial sunscreen oils used as controls confirm the correctness of performing the Mansur's method in this study. However, this dilution method has proven to be fundamentally flawed in determining the SPF value of substances with such negligible photoprotection as most vegetable oils can provide. An SPF value of less than 1, which can be determined by this Mansur's method, is physiologically impossible and meaningless.

The topic of free radicals and related antioxidants is greatly discussed nowadays. Antioxidants help to neutralize free radicals before damaging cells. In the absence of antioxidants, a phenomenon called oxidative stress occurs. Oxidative stress can cause many diseases e.g. Alzheimer’s disease and cardiovascular diseases. Therefore, antioxidant activity of various compounds and the mechanism of their action have to be studied. Antioxidant activity and capacity are measured by in vitro and in vivo methods; in vitro methods are divided into two groups according to chemical reactions between free radicals and antioxidants. The first group is based on the transfer of hydrogen atoms (HAT), the second one on the transfer of electrons (ET). The most frequently used methods in the field of antioxidant power measurement are discussed in this work in terms of their principle, mechanism, methodology, the way of results evaluation and possible pitfalls.

Antioxidants are important substances used in the cosmetic and pharmaceutical fields that are able to block free radicals. These compounds can be incorporated into formulations for many reasons, such as release over time or preservation of the formulation activity and applicability. In the present study, a low-molecular-weight gel made with Boc-L-DOPA(Bn)2-OH was studied as suitable material to host antioxidants and improve their activity. The solvent change (DMSO/H2O) in combination with temperature was the technological procedure for the preparation of the gel. Two different antioxidants were tested: (1) α-tocopherol and (2) postbiotics. The antioxidant activity of α-tocopherol and of the postbiotics in the gel, measured by the (2,2-diphenyl-1-picryl-hydrazyl radical (DPPH) assay, showed higher values than those in the pure solvent. The antioxidant activity of the gel with 0.8 w/v% of gelator and α-tocopherol in the concentration range of 5–100 µM was 2.7–1.1 times higher on average than in the pure solvent. In the case of both postbiotics, the biggest difference was observed at 30% of postbiotics in the gel with 0.5% of a gelator, when the antioxidant activity was 4.4 to 4.7 times higher than that in the pure solvent.

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Due to adverse effects of free radicals on human skin and increasing consumer demand for natural ingredients, essential oils from basil, Ceylon cinnamon bark, clove, juniper, lavender, oregano, rosemary, tea tree, thyme, and ylang-ylang were assessed for their antiradical activity. The oils were evaluated in the concentration range of 5—0.1 mg·mL−1, in which the three reference synthetic antioxidants are most often added to mass-produced cosmetics. Among all examined samples, C. cinnamon oil at a concentration of 5 mg·mL−1 showed the strongest DPPH radical scavenging activity (0.41 mg·mL−1 IC50), followed by clove oil, BHA, α-tocopherol, and BHT (0.82, 0.84, 0.88 and 0.93 mg·mL−1 IC50), respectively. At the same concentration, the reduction power of C. cinnamon oil was higher (1.64 mg·mL−1 Trolox Eq.) than that of α-tocopherol and BHT (1.42 and 0.80 mmol·L−1 Trolox Eq., respectively) but lower than that of BHA (1.81 mmol·L–1 Trolox Eq.). Antiradical activity of the other eight essential oils was low or negligible. C. cinnamon oil and clove oil are promising antiradical agents for skin care but according to our GC-MS analysis, these oils contain 0.29 % of cinnamaldehyde, 0.03 % of linalool, 0.02 % of D-limonene, and 0.02 % of eugenol or 0.41 % of eugenol and 0.002 % of linalool, respectively, which are monitored contact allergens in cosmetics. Such a product is not be suitable for consumers allergic to these substances but for the vast majority of consumers it does not pose a risk in terms of allergic manifestations.