Magdalena Stelmach

People are paying more and more attention to their physical appearance. One way is the use of cosmetics containing antioxidants that slow down the skin ageing process. The application of photoprotective agents is another factor that protects the skin against ageing. Preparations based on natural raw materials are considered to be more safe. The evaluation of both antioxidant and photoprotective potential seems to be of interest for formulating new cosmetics. The aim of this study was to evaluate the antioxidant and in vitro photoprotective potential of Lavandula angustifolia alcoholic extracts. Two methods, i.e., DPPH and ABTS, based on spectrophotometric analysis were applied to determine antioxidant activity. Additionally, the in vitro sun protection factor (SPF) of these extracts was determined and a correlation between this parameter and the antioxidant potential of the extracts was also evaluated. The extracts of dry flowers and herbs of lavender were prepared using ultrasound-assisted extraction. As extractants, four short-chain alcohols, i.e., methanol, ethanol, n-propanol, and isopropanol, in three concentrations were applied to obtain the extracts. To evaluate the stability of the extracts, the determination of antioxidant activity by the DPPH and ABTS methods as well as the SPF value in vitro were performed twice: immediately after the preparation of the extracts and twelve months later. Moreover, the GC-MS analysis of certain extracts was also performed. In extracts made in diluted alcohols, a higher antioxidant potential was observed. A similar observation was made for the in vitro SPF determination. A significant correlation was seen between the antioxidant activity determined by the ABTS method and SPF (for herbs analysed immediately after extract preparation and twelve months later, r = 0.713 and 0.936, respectively, and for flower extracts, r = 0.640 and 0.801, respectively). For the DPPH method, a significant correlation was found only for herb extracts (r = 0.520 and 0.623, respectively). In general, slightly higher antioxidant or photoprotective in vitro potential were observed in later-analysed extracts. However, no significant differences were noted between the antioxidant activity or the photoprotection factor of the extracts determined immediately after their preparation and twelve months later, except for the flower extracts evaluated using the DPPH method (p < 0.0001). A very high correlation was found between the SPF values for both herb and flower extracts evaluated immediately and twelve months later, r = 0.953 and 0.899, respectively. Based on the obtained results, the extracts of Lavandula angustifolia Hidcote Blue variety could be considered as a possible component of anti-ageing cosmetics.