Seasonal Variations in Carnosic Acid Content of Rosemary Correlates with Anthocyanins and Soluble Sugars

Seasonal variations may influence the quality and quantity of biologically active ingredients in medicinal plants. Rosemary (Rosmarinus officinalis L.) a member of the Lamiaceae family, contains valuable antioxidant, anticancer and antibacterial substances, including Carnosic acid (CA). Here, the fluctuations of important active compounds present in rosemary leaf extracts collected in Golestan, Iran were studied during the year of 2012-2013. Plant phenolics, flavonoids, ascorbates, anthocyanins and soluble sugars were analyzed spectrophotometrically, while CA content was measured by High Performance Liquid Chromatography (HPLC). The highest amounts of total flavonoids occurred in autumn; while CA, phenolics, ascorbic acids and soluble sugars were greatest in winter, probably due to regional high precipitation and subtle winters. Most of the above indicated active compounds were low in early summer. Furthermore, total anthocyanins and soluble sugars showed significant positive correlations with CA over the year. These data suggest that rosemary extracts from the collected leaves in winter contain greater amounts of biologically active compounds; and can be used for standardization of plant materials harvested throughout a year.