Positive effect of Cu and yeast extract elicitors on the content of rosmarinic acid in Melissa offisinalis L.

Lemon balm(Mellissa offisinalis L.) belongs to the Lamiaceae family with medicinal properties such as anti-bacterial, anti-depressants, anti-inflammatory, anti-cancer and anti-viral effects. The most pharmacological effects of this plant are related to its active ingredient, rosmarinic acid. In this research, the effects of different concentration of elicitors, yeast extract (0, 0.5, 1 and 2 mg/mL) and copper (0, 4, 8 and 16 μM) at different time intervals (4, 8 and 16 h) were investigated on rosmarinic acid and total flavonoid contents in 30-day-old seedlings of lemon balm greenhouse conditions. Results showed a significant effect of yeast extract on rosmarinic acid production, especially after 4 and 8 hours of treatment with this elicitor. The highest amount of this compound was observed in seedlings treated with 1 mg/mL of this elicitor. On the other hand, copper elicitor at all used concentrations and the duration time of treatment (except for 4 μM for 16 hours) significantly increased rosmarinic acid production, so that this elicitor at concentration of 8 µM for 8 hours treatment could induce rosmarinic acid level about 7-fold. It seems that the elevated level of this active ingredient under treatment with these elicitors is due to the induction of reactive oxygen radicals and jasmonic acid biosynthesis and subsequently expression of some genes involving in rosmaric acid biosynthesis.