Evaluation of Phytochemical and Biochemical Patterns of Lemon Verbena (Lippia citriodora H.B.K.) at Different Temperatures

Lemon verbena (Lippia citriodora H.B.K.) from Verbenaceae family, as an aromatic and medicinal plant, has attracted interests for its valuable essential oil (EO). This study was conducted to evaluate the effect of various temperatures on phytochemical, biochemical, and allometric traits of lemon verbena leaves.

The experiment was designed on the basis of randomized complete block design (RCBD) with treatments of 5, 10, 15, 20, and 25 °C, and three replications.

The results showed that the EO content, main components, and chemical classes, except for oxygenated sesquiterpenes were enhanced by increasing the temperature from 5 to 25 ° C, while pigments, total soluble solid, proline, and soluble proteins were conversely decreased by increasing temperature. The highest fraction of variance among these variables was observed in the neral, EO, polyphenols and anthocyanins, respectively. According to cluster analysis (CA), the effect of temperature on the content of EO, main components, and chemical classes were classified into three groups (A: 5 and 10 °C, B: 15 and 20 °C, and C: 25 °C). Also, dendrogram cluster analysis showed three temperature groups (A: 5 °C, B: 10 °C, and C: 15-25 °C) on the basis of biochemical traits.

The present study showed that the content of oxygenated sesquiterpenes and antioxidant pigments in contrast to the amount of EO were severely increased by decreasing the environmental temperature. These results clarify the quality and economic value of this plant at the time of harvesting and environmental conditions for the pharmaceuticals, health, and food industries.