Variability in the polyphenolic composition and antioxidant ability of wild Rosmarinus officinalis L. collected in Spain

Rosmarinus officinalis L. is an aromatic species spontaneously growing in the Mediterranean area. The influence of the substrate composition and phenologic stage of the plant in its chemical composition is known [1,2,3]. In this work, thirteen samples of spontaneous populations of Rosemary were collected in Spain. The phenolic composition of the methanolic extracts was analysed by HPLC within a photodiode array detection and a reversed-phase analytical column, with a mobile phase consisting in Methanol and H2O/Acetic acid in gradient elution. Injection volume was 10 µl and every sample was analyzed in triplicate. Identification of seventeen polyphenolic compounds was performed by comparison of their retention times with those of pure authentic standards: rutin, quercetin, luteolin, kaempferol, myricetin, hesperidin, isovitexin, hesperetin, quercitrin, apigenin, apigenin-7-glucoside, arbutin and 3,5-dihydroxy-benzoic, isovanillic, gentisic, chlorogenic and ursolic acids. The antioxidant ability of the extracts was evaluated by the Oxygen Radical Absorbance Capacity (ORAC) method with a FLUOstar OPTIMA fluorimeter. Total phenolic content ranged between 27.43 and 100.7 µg/ml (samples 1 and 6, respectively), with a wide difference in their phenolic composition: sample 1 shows a lower content in phenolic acids, myricetin being the main flavonoid; the main flavonoid in sample 6 is rutin followed by myricetin. Chlorogenic acid is the main phenolic acid in every sample except for samples 4 and 13; sample 9 shows the highest rosmarinic acid content. This variation may be related to geographic distribution of the specimens, as plants were collected at the same developmental stage. The wide difference in the phenolic content is not related to the ORAC analysis results, with values ranging from 2.45 to 3.25, so the antioxidant activity may be related to the presence of phenolic and flavonoid compounds but not completely attributed to these kind of compounds.

Keywords: rosmarinus pfficinalis, polyphenols, flavonoids, phenolic acids, antioxidant activity

References:

[1] Palomino et al., 2010. Acta Hortic. 860: 249 – 253.

[2] Varela et al., 2009. Acta Hortic. 826: 167 – 174.

[3] Papageorgiou et al., 2008. J Agric Food Chem. 56: 7254 – 7264.