Optimization of callus induction with enhancing production of phenolic compounds production and antioxidants activity in callus cultures of carob (Ceratonia siliqua L.)

Carob (Ceratonia siliqua L.) is an important Mediterranean plant species with worldwide commercial and medicinal uses. The establishment of a callus culture protocol as an alternative system to produce polyphenols of chemical and pharmaceutical interest was made in the present study for the first time in carob. Explant type and the light regime are two important factors that influence morphogenic responses and biochemical production. Maximal callus induction (100 %) and biomass accumulation were obtained in cotyledon explants under both tested light regimes (16-h photoperiod and darkness). However, leaf-derived callus produced higher amounts of polyphenols (TPC) and flavonoids (TFC) but a lower amount of total condensed tannins (TCT) as compared to cotyledon-derived callus. The light treatment has significantly increased TCT content but decreased the antioxidant activity in carob callus cultures. Strong and positive correlations were obtained between TPC, TFC, and the antioxidant activities with correlation coefficients in range 0.68 – 0.98. The obtained results indicated that calli of C. siliqua have the potential for enhanced production of phenolic compounds with antioxidant activity that is favored by cultivation under dark condition.