Rosmarinic acid biosynthesis: Investigations of enzyme activity and genes in cell cultures of Melissa officinalis

Melissa officinalis or lemon balm, a perennial Lamiaceae, is a famous herbal remedy in the treatment of nervous or/and gastro-intestinal complaints. Its most important compound is rosmarinic acid (RA) with proven anti-oxidative, anti-inflammatory, antimicrobial and antiviral properties that is used in the treatment of cold sore (Herpes simplex) and as a food preservative [1]. RA is widely distributed in the plant kingdom, and it is a preformed constitutively accumulated defense compound and serves as a protection against herbivores.

Cell cultures are a good experimental system, because they can accumulate RA in high amounts during short time periods. The amount of RA accumulation depends on the total sugar content of the medium, and can be easily enhanced by addition of elicitors like methyl jasmonate [2]. Suspension cultures of M. officinalis accumulate RA up to 4% of the dry weight in medium with 5% sucrose or 8% after elicitation with methyl jasmonate. The biosynthesis of RA starts with two parallel pathways beginning with either phenylalanine or tyrosine that are finally connected by an ester forming reaction [3]. All eight enzymes involved will be characterized in cell cultures of M. officinalis. In addition, several of the encoding cDNAs, namely phenylalanine ammonia-lyase, hydroxycinnamic acid:CoA ligase and rosmarinic acid synthase, could be cloned.

References:

1. Wöbling, R.H., Leonhardt, K. (1994) Phytomedicines 1:25–31

2. Petersen, M., Häusler, E. et al. (1994) Plant Cell Tiss Org Cult 38:171–179

3. Petersen, M., Häusler, E. et al. (1993) Planta 189:10–14