Study on lawsone derivative formation in in vitro cultures of Impatients balsamina L.

Abstract

Callus, cell suspension and root cultures of Impatiens balsamina L. were successfully established from young leaf explants by manipulation of plant growth regulators in B5 medium. These in vitro cultures were maintained and evaluated for their potential in producing 2-hydroxy-1,4-naphthoquinone (lawsone) and 2-methoxy-1,4naphthoquinone, the two active constituents in I. balsamina plant. A method of double-development thin layer chromatography was developed carefully to ensure simultaneous detection of both natural naphthoquinones in the crude extracts of various in vitro cultures and the plants. Among the three different types of I. balsamina cultures, lawsone was detected in the root cultures, 2-methoxy-1,4-naphthoquinone in the callus cultures whereas neither of them was found in the cell suspension cultures. Quantitative analysis of both naphthoquinones produced by the cultures was carried out by the method of TLC-densitometry. While the callus cultures contained only 0.004 % 2-methoxy-1,4naphthoquinone, the root cultures appeared to accumulate lawsone to the level of as high% dry weight which is almost four times of the content found in the intact plant. Careful examination of the chemical constituents extractable from the root cultures showed a pattern that was very different from the one obtained from the whole root. Time-couse study of lawsone production by the root cultures showed high fluctuation of the naphthoquinone formation during a growth period of 20 days. In the whole plant, the content 2-methoxy-1,4-naphthoquinone was determined to be 0.130, 0.075 and 0.032 % in the leaves, stems and roots, respectively, and lawsone was found mainly in the leaves with 0.045 % dry weight. Apparently, this is the first report on the formation of lawsone in I. balsamina root cultures and on the quantitative distribution of lawsone and its methyl ether in the whole plant.