Helichrysum italicum (Roth) G Don: Seasonal variations of phenolic antioxidants

Autor: Generalić Mekinić, Ivana, Šimat, Vida, Mariani, Anja, Katalinić, Ana, Katalinić, Višnja, Ljubenkov, Ivica, Skroza, Danijela
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Popis: Oxidation of food components is one of the major causes of food deterioration which causes changes in chemical, biochemical and sensory properties of foods, its quality and nutritional value. Therefore, there is a great demand in food industry for natural ingredients that effectively inhibit these degradation processes. Spices and herbs have been used as flavouring agents or food preservatives since ancient times, and as non-toxic and natural substances are of special interest due of their strong antioxidant activity, which exceeds the effect of many currently used synthetic antioxidants. As the composition and bioactivity of plant material depends on numerous abiotic factors, among which the vegetation period is one of the most important, this study aimed to investigate the influence of the phenophase on phenolic and antioxidant profile of the widely-used medicinal herb and spice - Helichrysum italicum (curry plant, Asteraceae). The plant material was collected in different phenophases during the one-year vegetation period (12 samples from January to December) at the ecologically clean area of the Vrana Lake Nature Park (Middle Dalmatia, Croatia). Total phenolics in prepared plant extracts (1 g in 10 mL of 50% MetOH, extraction 1 hour at 50°C in ultrasonic bath) were determined by Folin-Ciocalteu assay (1) whereas the individual phenolics were identified and quantified by high performance liquid chromatography (HPLC) (2). The antioxidant activity of the extracts was evaluated by means of a multiple method approach using Ferric Reducing Antioxidant Power (FRAP) method (3), by scavenging free radical 2, 2-diphenyl-1-picrilhydrazil (DPPH) (4) and using Briggs Rauscher (BR) oscillating reaction (2). The main meteorological parameters ; the average monthly temperature, rainfall and cloud cover were also recorded. All of the obtained results and parameters were submitted to multivariate principal-component analysis (PCA), to achieve a better visualization of the different data sets. In this study, H. italicum was collected during one-year vegetation period and the highest content of total phenolics was recorded in extracts from June and July, 5914 and 6080 mg GAE/L, respectively. The presence of the individual phenolics (mainly free phenolic acids) was confirmed by HPLC, with carnosolic acid detected in highest concentration (165 mg/L in sample from June). The reducing activity (detected as FRAP value) and free radical scavenging activity (detected as DPPH and BR) also provided best results for extracts collected in summer periods what correlated with the recorded meteorological parameters. The obtained results once more confirm the fact that the presence of phytochemicals in high concentrations, like phenolics, affects biological activity of plant extracts. Among other different factors, plant vegetation period has exceptional effect on the content of these valuable secondary metabolites and therefore, consequently, on its antioxidant activity. Our results suggest that H. italicum is a great source of valuable phytochemicals, especially samples collected in summer (during the flowering), what makes this plant especially interesting for food, cosmetic and pharmaceutical industry.
Databáze: OpenAIRE