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

Abstract

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.

Keywords::

• Lawsone
• luteolin
• echinocystic acid
• 2,3-dihydroxy-1,4-naphthoquinone
• phthalic acid
• p-hydroxybenzoic acid
• isofraxidin
• scopoletin
• spinasterol