Oil stability index and biological activities of Achillea biebersteinii and Achillea wilhelmsii extracts as influenced by various ultrasound intensities

•Ultrasound-assisted extraction (UAE) is known to improve the extraction yield of phytochemicals.•The effects of UAE at different intensities vs. maceration were tested on the biological activities of two Achillea species.•The extraction of phenolics and flavonoids was increased at higher Ultrasound intensities.•Antioxidant and antimicrobial properties were higher in Achillea biebersteinii vs. Achillea wilhelmsii.•High-intensity ultrasound improves both extraction efficiency and biological activities of herbal extracts.

Comparing the effect of Ultrasound-assisted extraction (UAE) at different intensities vs. maceration as a traditional method in terms of total phenolic content (TPC), flavonoid content (TF) as well as oil stability index, antioxidant and antimicrobial properties of both Achillea biebersteinii and Achillea wilhelmsii was aimed. Aerial parts of A. biebersteinii and A. wilhelmsii were extracted by maceration and UAE method at 40%, 70% and 100% high intensities using methanol 80% v/v as solvent. There was a significant association between the ultrasound intensities and extraction yield of dried extracts, phenolics and flavonoids in both tested species. A. biebersteinii yielded higher amounts of dried extracts, phenolics, flavonoids, radical scavenging activity and reducing power comparing to A. wilhelmsii. Meanwhile, the antioxidant activity for both Achillea species extracted by UAE method was improved comparing to maceration. Evaluation of the oil stability index (OSI) using Rancimat test indicated that UAE method improves the stability of the oil enriched by A. biebersteinii extract more comparing to A. wilhelmsii. HPLC results showed that five major phenolic compounds were Gallic acid, P-coumaric acid, Caffeic acid, Ferulic acid and Chlorogenic acid. Furthermore, a higher antibacterial activity was observed from A. biebersteinii extracted by UAE method at different intensities in front of maceration extracts on tested microorganisms (Listeria monocytogenes, Bacillus cereus and different strains of resistant Staphylococcus aureus) comparing to A. wilhelmsii. Scanning electron microscopy (SEM) demonstrated that UAE method had a remarkable impact on the surface morphology of the glands and extraction of phytochemicals of Achillea extracts compare to maceration.