qualitative and quantitative evaluation of essential oil of catnip (nepeta cataria l.) under different drying conditions

Background: drying is the most common way to preserve quality of aromatic and medicinal plants. chosen drying methods can affect on the essential oil content and composition of medicinal plants.objective: this study aimed to assess the changes in essential oil constitutes of catnip aerial part under various drying methods.methods: the experiment was performed as the randomized complete block design (rcbd) with 10 treatments and 3 replications. the treatments were included the freshly harvested plants, sundrying, shadedrying, ovendrying at 35, 45, and 55 °c, microwavedrying at 100 and 200 w, and initial sundrying followed by subsequent shadedrying and ovendrying at 45 °c.results: the result indicated that the various drying methods had a significant effect (p le; 0.01) on the essential oil content and compositions. the highest amount of essential oil was observed in the ovendrying at 55 °c. gcms analysis revealed the presence 9 compounds in the essential oil of catnip, which three isomers of nepetalactone with a predominance of 4a alpha;, 7 alpha;, 7a beta;nepetalactone were major essential oil components. although, the amount of 4a alpha;, 7 alpha;, 7a beta;nepetalactone were reduced by ovendrying at 55 °c, but other the isomers of nepetalactone were increased. however, the total content of three isomers of nepetalactone were equal in the fresh catnip with the dried plants by the oven drier at 55 °c.conclusion: in general, the ovendrying at 55 °c is recommended as an effective method to dry the catnip.