Optimization of extraction of bioactive phenolics and their antioxidant potential from callus and leaf extracts of Citrus sinensis (L.) Osbeck, C. reticulata Blanco and C. maxima (Burm.) Merr.

The present study was conducted with an objective of optimizing extraction conditions for achieving maximum recovery of total phenolic content (TPC), total flavonoid content (TFC) and antioxidant potential in terms of radical scavenging activity (RSA) from ethanolic extracts of callus cultures and leaf tissues of three citrus species i.e. sweet orange (Citrus sinensis (L.) Osbeck), mandarin (Citrus reticulata Blanco) and pummelo (Citrus maxima (Burm.) Merr.). The callus was obtained from the seeds germinated under in vitro conditions. The extracts from callus cultures and leaf tissues were prepared in ethanol solutions (25%, 50% and 75%) by ultrasound-assisted extraction at different temperatures (30, 50 and 70 degrees C) and extraction times (10, 20 and 30 min). The results revealed that the extraction conditions of ethanol: water ratio of 50% at 50 degrees C for 30 min were the best in recovering maximum amounts of TPC, TFC and RSA. Analysis of variance was performed to identify various optimization conditions. A correlation analysis was performed to effect the interaction of phenols and flavonoids on antioxidant potential of callus cultures and leaf tissues in three citrus species. It was concluded that callus and leaves of the citrus species possess great potential for their use in production of bioactive compounds.