Quantitative HPLC determination of naphthoquinones in Impatiens balsamina leaves

Impatiens balsamina L. has been traditionally used for the treatment of wounds, abscesses and ingrown nails [1]. Naphthoquinones, lawsone and lawsone methyl ether were found to be a group of the active constituents exhibiting antifungal and antibacterial activities [2]. Bilawsone has been reported as a non-natural occurring naphthoquinone found in I. balsamina root cultures [3] and an antipruritic agent [4]. As part of our interest in the quantitative determination of naphthoquinones in I. balsamina leaf extract, an extraction method and simultaneous quantification of the naphthoquinones through HPLC were developed. A reversed-phase high performance liquid chromatographic method is described for the simultaneous determination of lawsone, lawsone methyl ether and bilawsone in I. balsamina leaves. The method involved the use of a Discovery® C18 column (5µm, 4.6×150mm) with the mixture of 2% aqueous acetic acid-methanol (gradient elution from 25% methanol to 55% methanol in 50 minutes) as the mobile phase and detection at 280nm. The parameters of linearity, repeatability, reproducibility, accuracy and specificity of the method were evaluated. The recovery of the method was 92.5–95.3% and linearity (r²≥0.9998) was obtained for all naphthoquinones. A high degree of specificity as well as repeatability and reproducibility (R.S.D. values less than 5%) were also achieved. The solvent for extraction of naphthoquinones from I. balsamina leaves was examined in order to increase the naphthoquinone content of the extract. A mixture of 50% chloroform in methanol was capable of increasing the naphthoquinone content in the extract up to 0.29%w/w.

Acknowledgements: Prince of Songkla University, The Thailand Research Fund.

References: 1. Fransworth, NR., Bunyapraphatsara, N. (1992) Thai Medicinal Plants: Recommended for primary health care system. Bangkok. 2. Fransworth, NR., Cordell, GA. (1976) Lloydia 39:420–455. 3. Panichayipakaranant, P. et al. (1995) Phytochemistry 40:1141–1143. 4. Oku, H. et al. (2002) Biol. Pharm. Bull. 25:137–139.