Changes in bioactive phytochemical content and in vitro antioxidant activity of carob (Ceratonia siliqua L.) as influenced by fruit ripening

•Phytochemicals and antioxidant activity of three carob varieties were determined.•Phytochemicals of carob were greatly affected by the variety and the ripening stage.•The unripe carob samples demonstrated the highest phytochemical contents.•Carob extracts exhibited the best antioxidant activity in the unripe stage.•The unripe carob can be considered as an excellent source of natural antioxidants.

In the present study, three varieties (Wild, Fleshy and Sisam) of carob (Ceratonia siliqua L.) pods were analyzed for their bioactive phytochemical content and antioxidant activities (AA) at three ripening stages. The results showed that the samples have the highest total phenolic (TPC), total flavonoid (TFC) and ascorbic acid content (AAC) in the unripe stage. The antioxidant activity examined using free radical scavenging effect against 2-2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing power (FRP) and ferrous iron chelating (FIC) assays decreased significantly throughout the ripening. Extremely significant correlations (p < 0.001) were found between phytochemical compound contents (TPC, TFC and AAC) and assessed antioxidant activities, except between AAC and FIC where just a very significant correlation (p < 0.01) was recorded. Our data revealed that extracts of unripe C. siliqua L. are an excellent source of natural antioxidants that might be more widely used in cosmetic, pharmaceutical and food industries.

Graphical abstractThe in vitro antioxidant activity of aqueous extracts from carob pulp was investigated. Significant differences were observed in the phytochemical content and the antioxidant power. Extracts of unripe carob recorded the highest total phenolic, total flavonoid and ascorbic acid contents. These extracts also exhibited the highest DPPH radical scavenging activity, ferric reducing power and ferrous iron chelating ability. Extracts of unripe carob could be useful as natural antioxidant agent for food industry.Download full-size image