An efficient strategy for enhancement of bioactive compounds by protocorm-like body culture of Dendrobium candidum

• The effects of methyl jasmonate and salicylic acid on biomass and bioactive compound accumulation in protocorm-like bodies of Dendrobium candidum are investigated.
• The methyl jasmonate of 75 μM is suitable for production of bioactive compounds.
• Methyl jasmonate should treat protocorm-like bodies after 30 days of bioreactor culture.
• The suitable treatment duration of methyl jasmonate differs among types of bioactive compounds.
• Protocorm-like bodies treated with the methyl jasmonate have higher antioxidant activity.

As the effective elicitors, methyl jasmonate (MeJA) and salicylic acid (SA) have been widely used in plant cell and organ culture for improvement of bioactive compound accumulation. The protocorm-like bodies (PLBs) of Dendrobium candidum were stimulated with different amounts of methyl jasmonate (MeJA) and salicylic acid (SA) during suspension culture to improve the production of bioactive compounds in PLBs. The optimal concentration of MeJA and SA varied among the types of bioactive compounds. Treatment with 75 μM MeJA enhanced the production of alkaloids, polysaccharides, and flavonoids, whereas 100 μM MeJA improved phenolic production. An elicitation effect was also exhibited in SA, such that 75 μM SA yielded the highest accumulation of alkaloids and polysaccharides, whereas 100 μM SA generated the highest amount of flavonoids. Moreover, SA concentration did not affect phenolic production. Furthermore, MeJA was used to treat PLBs after 30 days of bioreactor culture to investigate the effect on large-scale applications. The highest amounts of alkaloids and polysaccharides were determined after 4 days of MeJA elicitation, and those of phenolics and flavonoids were detected after 10 days of MeJA treatment during PLB bioreactor culture. Bioactive compound content and antioxidant activity in bioreactor-cultured PLBs were compared with those in whole plants. The contents of alkaloids, polysaccharides, phenolics, and flavonoids in the PLBs were higher than those in the plants. Protocorm-like bodies treated with MeJA also contained the maximum amount of bioactive compounds. The antioxidant activity of MeJA-treated PLBs was also evaluated using the following parameters: 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, reducing power, and ferrous ion (Fe2+) chelating activity, which were higher than those in the extracts of PLBs without MeJA treatment and plants. This study reveals that MeJA as an efficent elicitor can be used for the mass production of bioactive compounds by PLB culture using bioreactor culture systems and the obtained PLBs can be provided to the commercial production of D. candidum products.