Plant hydrolates - Antioxidant properties, chemical composition and potential applications

Hydrolates, are by-products of the hydrodistillation of plants. They consist of the distillation water in which very small amounts of essential oils remain dispersed. Hydrosols are widely used in cosmetics. One of the greatest challenges in skin care, whether it is healthy or affected by a pathological condition, is how to minimize oxidative stress. Extract also lend themselves to applications in the agri-food industry, to inhibit the development of pathological microorganisms in food and to remove biofilms constituting a threat to public health in food, pharmaceuticals and beauty products. Therefore, the aim of this study was to analyze the antioxidant potential of hydrosols available in the cosmetics market, taking into account for the first time in scientific literature not only plant species, but also origin (country, farming system, part of plant) and method of preservation. Antioxidant activity, expressed as percentage inhibition of DPPH (1,1-diphenyl-2-picrylhydrazyl), ferric ion reducing antioxidant power (FRAP) and content of polyphenolic compounds (Folin-Ciocalteu method), was determined in seventeen hydrosols by spectrophotometric methods. Antioxidant potential was in the range of 4.43-39.87% of DPPH radical inhibition and 1325.65-5794.38 µM Fe(II)/L. Total phenolic content (TPC) in the hydrosols amounted to 9.33-44.23 mg GAE/L, while total flavonoid content (TFC) ranged from 1.48 to 14.82 mg rutin/L. The hydrosols had a pH in the range of 3.31-5.42. Conclusions: Plant hydrosols appear to have a high antioxidant potential, which depends on not only the plant species, but also its origin, part of the plant from which the hydrosol was obtained and the preservation method used in the finished product.