Rhinacanthin production from hairy root cultures of Rhinacanthus nasutus (L.) Kurz

Rhinacanthus nasutus (L.) Kurz (family Acanthaceae) produces several important bioactive molecules. Its leaves and roots were widely used in traditional systems of medicine for the treatment of cancer and other serious diseases. In the present study, the contents of three potent natural naphthoquinone esters, rhinacanthin (RC)-C, RC-D, and RC-N, were evaluated in R. nasutus hairy root cultures. Hairy roots were induced from leaves, stems, and cotyledons following transformation with Agrobacterium rhizogenes (MTCC Strain No. 532). The highest frequency (73%) of hairy root induction was observed with cotyledons. Four media (½ Murashige and Skoog [MS], MS, Schenk and Hildebrandt medium, and Woody Plant Medium) were then compared for their effects on hairy root growth and RC production. The transgenic status of hairy roots was confirmed by PCR analysis and Southern hybridization analysis. A time course study revealed that the highest hairy root biomass (0.89 g/flask dry weight [DW]) and RC contents (RC-C, 3.8 mg/g DW; RC-D, 0.43 mg/g DW; and RC-N, 0.18 mg/g DW) were observed following culture on MS medium 6 wk after culture initiation. The root biomass (1.41 g DW/flask) and RC contents (RC-C, 4.4 mg/g DW; RC-D, 0.69 mg/g DW; and RC-N, 0.21 mg/g DW) were further increased by the use of 4% sucrose. The growth and RC production from hairy roots of R. nasutus demonstrated in the present study may offer an effective and reliable alternative for the exploitation of this medicinal plant.