The present research work describes the effects of 2,4-dichlorophenoxyacetic acid (2,4-D)/Ben-zylaminopurine (BAP) ratio on callus induction, total phenolic and ascorbic acid production, and antioxidant activities in leafderived calli of Crataegus azarolus (hawthorn). The supplementation of 1.0 mg/L 2,4-D and 1.0 mg/L BAP to MS medium was found to be the most efficient for callus induction (as percentage and fresh weigh). The results of biochemical analysis showed that the highest total phenolic contents were obtained in callus cultured on MS medium supplemented with 2.0 mg/L 2,4-D and 1.0 mg/L BAP (52 ± 0.56 mg GAE/g DM) and were significantly lower than those of intact leaves (76±1.72mg GAE/g DM). However, the highest ascorbic acid contents were found in callus cultured on MS medium supplemented with 1.0 mg/L 2,4-D and 0.5 mg/L BAP (0.96 ± 0.13 mg AAE/g DM) and these amounts were statistically similar to those found in leaf tissues (0.74 ± 0.07 mg AAE/g DM). Antioxidant activities of callus extracts were determined using two TEAC assays and results showed that extract of callus cultured on MS medium supplemented with 2.0 mg/L 2,4-D and 1.0 mg/L BAP have the greatest antiradical activities against DPPH (124 ± 2.92 mg TE/g DM) and ABTS (0.19 ± 0.02 mg TE/g DM) compared to the leaves of field-grown plant. Thus, the use of high level of 2,4-D over BAP can be suitable to enhance the quality more than the quantity of bioactive compounds in leaf callus culture of hawthorn.

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