Influence of Phytohormones on Growth and Production of Ajmalicine by Multiple Shoot Cultures of Catharanthus roseus

Multiple shoots were induced from shoot tip explants of Catharanthus roseus and growth rate as well as ajmalicine production were also studied. Shoot cultures were developed on MS medium supplemented with high concentrations of cytokinins BAP (8.90 ?M) or Kn (9.30 ?M) in combination with low concentrations of auxins NAA (2.69 ?M) or IAA (2.85 ?M). The concentration of ajmalicine varied according to phytohormones concentrations and combinations into the culture medium and age of the shoot cultures. MS medium fortified with BA and IAA enhanced the growth of multiple shoots and produced maximum biomass (23.1 g/ 100g DW) on day 25 but ajmalicine yield affected. Quantitative HPLC assay of the shoot extracts showed that highest ajmalicine production (0.329% DW) was obtained when shoot cultures were grown on MS medium with the combination of KN (9.30 ?M) and NAA (2.69 ?M) for 25 days. Shoot cultures accumulated 1.5 fold more ajmalicine in NAA and Kn supplemented medium compared with the NAA and BA. The results show that optimum growth rate obtained in medium containing NAA and Kn produced 38.7-fold more ajmalicine compared to IAA and BA, which attained highest growth rate of shoot cultures. Ajmalicine concentration was 4.8-fold higher in 25-day-old shoot cultures compared to leaves of one-year-old intact plants. Studies on phytohormones regulation and product synthesis by multiple shoot cultures indicated that ajmalicine production was not correlated with growth rate. Anticancer alkaloids vincristine and vinblastine were not present in shoot cultures.