The current study reports synthesis, characterization, and bioactivities (antibacterial and antioxidant) of silver nanoparticles (AgNPs) using Buxus wallichiana and Buxus sempervirens polyphenolic fractions (PPF). A response surface methodology (RSM) optimized ultrasound assisted extraction technique was used for extraction. Binary solvent systems [solvent system-I (70% ethanol and 30% water), solvent system-II (50% ethanol and 50% water), and solvent system-III (30% ethanol and 70% water)] at time (60, 90 min) and temperature (30 °C, 45 °C, 60 °C) were utilized for obtaining PPF. In AgNPs synthesis, reacting 1:1 to 1:15 proportions of the PPF and the silver salt solution, a proportion of 1:5 (PPF from SS-I), produced a higher yield of AgNPs as indicated by the increased absorbance intensity at the characteristic surface plasmon resonance peak (λmax 421 nm) in UV–Vis spectroscopic analysis compared to other tested ratios. Further, the synthesized AgNPs possessed an average size of 7.64 nm to 8.04 nm. Furthermore, the study reports that B. wallichiana and B. sempervirens contained high total phenolics and total flavonoids content (TPC and TFC). The PPF of B. wallichiana and B. sempervirens extracted with solvent system-I (SS-I) at 45 °C for 90 min, contained the highest TPC of 244.5±4.70 mg gallic acid equivalent/g (mg GAE/g) and 199.8±3.99 mg GAE/g, respectively. In addition, the TFC were found to be 182.7±5.11 mg quercetin equivalent/g (mg QE/g) and 203.7±4.92 mg QE/g, respectively. Assessing the antibacterial activity, the AgNPs and the PPF exhibited significant bacterial inhibition against Staphylococcus aureus and Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli with inhibition zone ranging from 8.00 mm to 20.0 mm. The antioxidant activity was found high ranging with IC50 values of 0.02 to 0.09 mg/mL. This is the first report describing green synthesis of biologically active AgNPs via B. wallichiana and B. sempervirens RSM optimized PPF.
Noor Ul Ain, Nargis Jamila, Naeem Khan, Ayesha Bibi, Raina Aman Qazi, Naheed Bibi