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Cnidium officinale Makino is an important medicinal plant of oriental clinics and is considered as the main source of phthalides, polyphenols, and flavonoids. However, there is no available report regarding the effect of different light colors on the secondary metabolites composition of C. officinale. In this study different light (dark, white, blue, red and red: blue) conditions were arranged to raise callus on MS medium containing 0.5 mg·L -1 of each 2,4-D and BAP. Callus grown in dark condition showed maximum (2.0 g) fresh weight with lower total phenolic and flavonoids contents. Also, in dark condition callus faced higher catalase (CAT) and guaiacol peroxidase (GPX) activities to avoid free radicals. Mix (red: blue) light condition favored the synthesis of phenolics and flavonoids in callus at the cost of higher ascorbate peroxidase (APX) and superoxide dismutase (SOD) enzymes expression. However, DPPH free radical scavenging activity was less variable among the samples from the different light conditions. Interestingly, the HPLC profile showed higher (28.3 μg·g -1 DW) phthalide accumulation in dark grown-cultures. Compared to other light conditions, 3-butyledinephthalide accumulation was higher (0.43 μg·g -1 DW) in white light-grown callus. These findings suggest that light conditions play an important role in the regulation of in vitro callus growth and synthesis of important medicinal compounds of C. officinale., (Copyright © 2019 Elsevier B.V. All rights reserved.)

This study reports the effect of explant type and plant growth regulators (PGRs) on callus induction in Cnidium officinale. Compared to stem, root explant showed maximum percent callus formation of 75% on Murashige and Skoog (MS) medium containing 2.3 µM 2,4-dichlorophenoxyacetic acid (2,4-D) and 2.2 µM benzyladenine (BA). At 30th day of callus culture on the said medium, callus fresh weight was sevenfold higher than other tested PGRs treatments. It was noted that MS medium supplemented with 27.1 µM 2,4-D showed the highest 0.30 mg g -1 DW of total phenols, while total flavonoids content reached to a maximum of 0.05 mg g -1 DW on the MS medium supplemented with 4.5 µM 2,4-D and 2.2 µM BA. Conversely, maximum (83.9%) DPPH free radical scavenging activity was observed in calli grown on the MS medium supplemented with 2.3 µM 2,4-D and 2.2 µM BA. The high-performance liquid chromatography (HPLC) analysis revealed higher phthalide content in callus than intact roots of in vitro plants. While 3-butylidenephthalide content in callus was comparable to the intact shoots and roots of in vitro grown C. officinale. The concentrations of 2,4-D played a significant role in the production of phthalide and 3-butylidenephthalide. Additional measures are recommended to further enhance their production in vitro.