Effect of methionine on production of naphthoquinones in Impatiens balsamina root cultures and detection of some secondary metabolites.

CONTEXT

Lawsone, lawsone methyl ether and 3,3'-methylelnebislawsone are the main active compounds of Impatiens balsamina L. (Balsaminaceae). These compounds possess various pharmacological activities that have been shown to assist with the treatment of skin diseases.

OBJECTIVE

This work focused on increased naphthoquinone production in I. basamina root cultures using methionine feeding.

MATERIALS AND METHODS

I. balsamina root cultures were maintained in liquid Gamborg's B5 medium supplemented with 0.1 mg/L α-naphthalene acetic acid, 0.1 mg/L kinetin, 1.0 mg/L 6-benzyladenine and 20 g/L sucrose. The effect of methionine concentration (50, 100, 300, 500 and 1000 mg/L) on naphthoquinone production of I. basamina root cultures was determined. Isolation of secondary metabolites from I. balsamina root cultures was also carried out.

RESULTS AND DISCUSSION

Feeding of 300 mg/L methionine to the root cultures at the beginning of the growth cycle increased the production of 3,3'-methylelnebislawsone almost two-fold (0.63 mg/g dry weight, compared to the control group 0.32 mg/g dry weight). Optimization of the feeding conditions showed that adding 500 mg/L methionine to a 21-day old root cultures increased production of lawsone methyl ether and 3,3'-methylenebislawsone up to 2.6- and 3.1-fold higher, respectively, compared to the controls. In addition, various pharmacologically interesting secondary metabolites were isolated from I. balsamina root cultures, such as a flavonoid, luteolin, a naphthoquinone, 2,3-dihydroxy-1,4-naphthoquinone, and a triterpenoid, echinocystic acid. This is the first report of the occurrence of these compounds in this plant.