Antioxidant activity of rosemary (Rosmarinus officinalis L.) and its in vitro inhibitory effect on Penicillium digitatum

The objective of this study was to evaluate rosemary (Rosmarinus officinalis L.) growing wild in Hammam Dalaa (Algeria) for total phenolic content, free radical scavenging activity (FRSA) and test the effect of its extracts on the growth of the green mold of citrus, Penicillium digitatum, under in vitro conditions. The results obtained using the Folin-Ciocalteu method showed a high content of the extract in polyphenols reaching 129 mg gallic acid equivalents/g and relatively low content of flavonoids (38mg of quercetin equivalents/g dry extract). In the DPPH assay the methanol extract exhibited a FRSA close to those of the synthetic antioxidants, tested as positive controls, and higher compared to that of the EO. The in vitro antifungal assay by means of different methods showed a clear inhibitory effect of the rosemary essential oil and methanol extract on P. digitatum. The inhibitory effect registered at the 6th day of incubation at 25 degrees C was between 5 to 79% when the essential oil was applied as fumigant at concentrations ranging from 10 to 50 mu l, and was between 13 and 50% when applied by contact bioassay at levels from 1000 to 3500 mu l/l. Spore germination was strongly affected by the oil applied by disk diffusion method. The methanol extract exhibited inhibition exceeding 50% of the fungus mycelial growth but at relatively high concentration 0.8g/l. These results support the studies on rosemary as a promising source of preservatives. (c) All Rights Reserved