In vitro propagation and bioactive compound accumulation in regenerated shoots of Dioscorea birmanica Prain & Burkill

Dioscorea birmanica Prain & Burkill is a Thai medicinal plant, which is often used with other medicinal plants for the treatment of cancers, AIDS, and septicemia diseases. Large numbers of this desirable plant can be produced using the plant tissue culture techniques. The objectives of this study were to investigate techniques of in vitro propagation and to examine the bioactive compounds: diosgenin-3-O-alpha-L-rhamnopyranosyl (1 -> 2)-beta-D-glucopyranoside (DBS1) content, total phenolic content, and antioxidant activity of the regenerated shoots compared to those of rhizomes growing in the field. For shoot induction, the highest numbers of shoots (2.8 +/- 0.5) and nodes per shoot (5.7 +/- 0.8) occurred after the single-nodal explants were cultured on Murashige and Skoog (MS) medium supplemented with 2 mg/l BA (6-benzyladenine) for 4 weeks. Shoot multiplication was achieved on MS medium supplemented with 0.01 % activated charcoal (AC) and 2 mg/l BA in combination with 0.1 mg/l IAA or 0.2 mg/l NAA. The regenerated shoots were rooted on 1/2 MS medium supplemented with 0.01 % AC, 2 mg/l BA and 4 mg/l NAA for 8 weeks. The survival percentage was 71.88 and small rhizomes developed after transplanting for 4-6 weeks. The quantities of 0.37 +/- 0.03 % (w/w) DBS1, 44.24 +/- 8.47 mg GAE/g dry extract total phenolic and DPPH radical scavenging assay with EC50 value of 53.67 +/- 4.16 mu g/ml were determined from the regenerated shoots, while 3.27 +/- 0.04 % (w/w) DBS1, 259.67 +/- 7.34 mg GAE/g dry extract total phenolic and DPPH radical scavenging assay with EC50 value of 11.42 +/- 3.28 mu g/ml were found in the mother rhizomes.