Optimization of ultrasonic extraction condition for maximal antioxidant, antimicrobial, and antityrosinase activity from Hibiscus cannabinus L. leaves by using the single factor experiment

A single factor experiment design was employed to optimize ultrasonic assisted extraction of Hibiscus cannabinus L. (kenaf) leaves. Ethanol concentration and extraction times (min) were optimized in the study as this extraction parameters were believed to have effect on the recovery of bioactive compounds derived from kenaf leaves extract (KLE). Considering all the results obtained from the experiment, it displayed that the 95 % ethanolic kenaf leaves that went through 3 min extraction was the optimum extraction condition, with significant highest (p < 0.05) of total flavonoid content (TFC) (48.20 ± 0.15 mgCHE/g), 2,2-Diphenyl-1-picrylhydrazyl (DPPH) (33.99 ± 1.58 mgTEAC/g) and 2,2′-Azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging assay (34.23 ± 0.18 mgTEAC/g). TFC was significantly correlated with DPPH and ABTS under the effects of ethanol concentration. The optimized KLE also showed high total phenolic content (TPC), ferric reducing antioxidant power (FRAP), and tyrosinase inhibitory activity. Besides, the optimized KLE were reported to be effective in bactericidal activity against five investigated pathogenic bacteria (Bacillus cereus, Staphylococcus epidermis, Salmonella, Pseudomonas aeruginosa, and Escherichia coli) with the minimum inhibitory concentration (MIC) values of 2.5, 5 and 10 mg/mL.