Abstract
Rosmarinus officinalis L. presents a high genetic variability, which is reflected in the chemical composition of the different individuals, and consequently in its biological activity, including antioxidant capacity. The aim of the present research was to correlate the chemical composition of methanolic extracts of the dried leaves of eight rosemary accessions with their antioxidant activity for the selection of plants to optimize the use of rosemary. The eight samples examined, starting from a collection of more than 160 individuals selected by BOTANE Ltd, were cultivated at Illapel, north central Chile, using the same cultivation techniques. The free radical-scavenging capacity was tested by the ability of extracts to bleach the stable 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH) and to inhibit superoxide anion (O2-) and hydroxyl radical (.OH) production. The metal chelating activity was estimated by the ferrozine assay. All extracts (1–8) contained high concentrations of carnosic acid, and to a minor extent rosmarinic acid, and exhibited antioxidant activity. However, extracts 7 and 8, containing 31.7 and 26.1% of carnosic acid, respectively, have shown a higher biological effect, confirming that the antioxidant activity of R. officinalis leaves is primarily related to this phenolic diterpene and suggesting that the measure of antioxidant activity could be considered a good method in the selection of this plant for its optimization. Interestingly, our experimental evidence also suggests that air pollution negatively influences the carnosic acid content. In fact, samples 3 and 4, with a low carnosic acid content, originated from a highly polluted metropolitan area of Santiago city.