Purpose: To investigate the effect of magnesium and calcium as abiotic elicitors on Valeriana officinalis hairy roots for scale-up production of valerenic acid.

Methods: Hairy roots were established in different explants of Valeriana officinalis via a mikimopine type strain of Agrobacterium rhizogenes ‘A13’. Transgenic status of hairy roots was confirmed by polymerase chain reaction (PCR) analysis of the rolB gene. Hairy roots of 28-day old cultures were exposed to magnesium and calcium (2 to 6-fold concentration of that present in normal Murashige and Skoog (MS) medium for 3 and 7 days. After elicitation, the cultures were grown in MS liquid medium without elicitors for 8 weeks. Valerenic acid content in hairy roots was analysed using high-performance liquid chromatography (HPLC) to determine the best yield conditions.

Results: Transformed cultures showed significant differences (p < 0.05) in valerenic acid content. The highest amount of valerenic acid (1.83 ± 0.06 mg/g dry weight (DW) was found in hairy root cultures exposed to 6-fold calcium for 7 days, which was 7.9 times higher than that of control culture (0.23 ± 0.01 mg/g DW).

Conclusion: The results show that concentration and exposure time to elicitors are important factors that affect the production of valerenic acid.