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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 °C) and extraction times (10, 20 and 30 min). The results revealed that the extraction conditions of ethanol: water ratio of 50% at 50 °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. [ABSTRACT FROM AUTHOR]

Different plant extracts have been utilized for biological synthesis of metal nanoparticles. However, no published literature compares the antimicrobial potential of silver nanoparticles (AgNPs) derived from extracts of mature fruit juice (SLF-AgNPs) versus callus (SLC-AgNPs) tissue of same plant. These SLF- and SLC-AgNPs exhibited variable physical and biological properties. Distinct UV-Vis absorption peak (at 250 nm) for SLF-AgNPs indicated formation of small-sized monodisperse particles. Both SLF-AgNPs (5 to 35 nm) and SLC-AgNPs (3 to 270 nm) exhibited quasi-spherical shapes. The FT-IR spectra showed occurrence of shared peaks at 3335, 1647, and 1080 cm−1 while SLC specific peaks at 1065, 1042 and 1017 cm−1. The SLF-AgNPs possessed higher DPPH free radical scavenging potential. These nanoparticles also showed better antibacterial and antimycotic action epitomized as higher inhibition zone diameters compared to SLC-AgNPs. This work can be furthered to identify predominant mechanism for improved antimicrobial potential of the synthesized AgNPs. [ABSTRACT FROM AUTHOR]