Effect of Microwave and Ultrasound-Assisted Extraction on the Phytochemical and In Vitro Biological Properties of Willow (Salix alba) Bark Aqueous and Ethanolic Extracts

White willow (Salix alba) is a medicinal plant used in folk medicine. In this study, aqueous and ethanolic willow bark extracts were obtained via ultrasonic-assisted extraction (UAE) and microwave-assisted extraction (MAE), and analyzed regarding their phytochemical (total phenolics, phenolic acids, flavonoids, and tannins) content and in vitro biological properties (antibacterial and antifungal activity, acetylcholinesterase AChE inhibitory activity and anti-inflammatory effects). The highest phenolic, tannin, and flavonoid contents were found for willow bark extracts obtained via microwave-assisted extraction using ethanol as a solvent (SA-ME). The polyphenol load of all MAE and UAE extracts was higher when conventional solid-liquid extraction was applied (& rho; < 0.05). The antioxidant capacities were stronger for microwave-assisted ethanolic extracts, with the lowest IC50 values of 12 & mu;g/mL for DPPH & BULL; and a value of 16 & mu;g/mL for ABTS & BULL;+, whereas the conventional extraction had the highest IC50 values (22 & mu;g/mL and 28 & mu;g/mL, respectively). Willow bark extract showed antibacterial activity against Gram-positive bacteria S. aureus and P. aeruginosa. AChE inhibitory activity was dependent on the extraction method and solvent used, and the highest inhibition among samples was observed for SA-ME. Taken altogether, our findings suggest that willow (Salix alba) bark extract obtained via ethanolic microwave-assisted extraction is a phytochemical-rich resource with in vitro, anti-inflammatory, and AchE inhibitory properties and, therefore, potential multiple medicinal end-uses.

Automated summary

In this study, aqueous and ethanolic extracts of white willow bark were obtained using different extraction methods. The extracts were analyzed for their phytochemical content and biological properties. The results showed that microwave-assisted ethanolic extracts had the highest phenolic, tannin, and flavonoid contents, as well as strong antioxidant activity. The extracts also exhibited antibacterial and anti-inflammatory effects. Overall, microwave-assisted ethanolic extraction of white willow bark could be a valuable resource for multiple medicinal uses.