Polyphenol contents and antioxidant activity of carob callus cultures

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-hour photoperiod and darkness). However, leaf callus produced a higher amount of polyphenols (TPC) and flavonoids (TFC) but a lower amount of total condensed tannins (TCT) as compared to cotyledon callus. Light treatment has significantly increased TCT content but decreased the antioxidant activity in carob callus cultures. Strong and positive correlations were obtained between TPC and TFC and the antioxidant activities with correlation coefficients ranging between 0.68 and 0.98. The obtained results indicate that calli of C. siliqua have the potential for enhanced production of phenolic compounds with antioxidant activity that is favored by culture under dark condition.