Comparative study of polyphenols and antioxidant capacity of sage (Salvia officinalis L.) from Mediterranean part of Croatia

Introduction. Sage (Salvia officinalis L.) contains phenolic compounds which possess strong antioxidant and antimicrobial properties (Dorman et al., 2003 ; Matkowski et al., 2006). The most abundant polyphenols in sage are caffeic acid derivates. Rosmarinic acid is present in highest level and is reported to be responsible for high antioxidant activity of sage (Cuvelier et al., 1996). The majority of flavonoids in sage are flavones of apigenin and luteolin and their glycosides. The objective of this study was to research the occurrence of polyphenols isolated using conventional (CE) and microwave assisted extraction (MAE) and antioxidant capacity (AOC) of dry sage harvested at Mediterranean part of Croatia. Materials and methods. Wild sage collected in august 2008 at Pirovac, Brac, Losinj, dried at warm, dark place and stored in paper bags at the room temperature. The polyphenols were extracted using water, 30% ethanol and acetone, refluxed in water bath (60oC/30 minutes) ; MAE was carried out using the same solvents and microwave power 500W, at 80oC/10 minutes. Total polyphenols (TP) were determined using Folin-Ciocalteu method ; individual phenolic acids and flavons were confirmed by HPLC UV/Vis/DAD ; AOC was evaluated using ferric reducing antioxidant power (FRAP) assay. Results and discussion. There was significant difference in the polyphenols contents among sage harvested at three different locations. In acetone and ethanolic extract the highest amount of TP was determined in sage from Losinj (52.30 and 44.76 mg RAE/g dm). The main polyphenolic compound in all sage samples was rosmarinic acid (RA) (60.15 to 74.12% ) followed by flavons. MAE significantly increased the content of polyphenols. Furthermore, extraction capacity of conventional ethanol or acetone solvent was significantly lower than MAE ethanol or acetone extractions. The high AOC in all sage samples was observed, and the highest values were determined in samples from Losinj. High correlation between TP and AOC (0.6865 to 0.9427) was observed. Conclusions. Rosmarinic acid was predominant in all sage samples. Flavon glycosides of luteolin and apigenin were determined in remarkable amounts. The place of harvesting signifficantly influenced on the polyphenol contents, and sage from island Losinj contained the highest amount of polyphenols as well AOC.