Optimization of Microwave-Assisted Extraction of Polyphenols from Lemon Myrtle: Comparison of Modern and Conventional Extraction Techniques Based on Bioactivity and Total Polyphenols in Dry Extracts

Abstract

The aromatic herb lemon myrtle is a good source of polyphenols, with high antioxidant and antimicrobial capacity. In this study, the green extraction technique microwave-assisted extraction (MAE) was applied and the extraction parameters were optimized using response surface methodology (RSM) to maximize the extraction yield of phenolic compound and antioxidant properties. Then, it was compared with other popular novel and conventional extraction techniques including ultrasound-assisted extraction (UAE) and shaking water bath (SWB) to identify the most effective technique for extraction of phenolic compounds from lemon myrtle. The results showed that the MAE parameters including radiation time, power, and sample to solvent ratio had a significant influence on the extraction yield of phenolic compounds and antioxidant capacity. The optimal MAE conditions were radiation time of 6 min, microwave power of 630 W, and sample to solvent ratio of 6 g/100 mL. Under optimal conditions, MAE dry extract had similar levels of total phenolic compounds (406.67 ± 8.57 mg GAE/g DW), flavonoids (384.57 ± 2.74 mg CE/g DW), proanthocyanidins (336.54 ± 7.09 mg CE/g DW), antioxidant properties, and antibacterial properties against (Staphylococcus lugdunensis and Bacillus cereus) with the other two methods. However, MAE is eight-times quicker and requires six-times less solvent volume as compared to UAE and SWB. Therefore, MAE is recommended for the extraction of polyphenols from lemon myrtle leaf.

Characterization of the Chemical Composition and Biological Activities of Bog Bilberry (Vaccinium uliginosum L.) Leaf Extracts Obtained via Various Extraction Techniques

“…Our results are in line with previous studies. For example, in the study of Saifullah et al [54], the antibacterial properties of their extracts prepared from modern techniques (MAE, UAE) and CE (SWB-shaking water bath) were not significantly different, a fact that could be due to the similarity of the phenolic compounds and antioxidant properties in the extracts obtained from these extraction techniques. In another study [55] evaluating the efficacy of two methods (agitation as the CE and UAE as the modern technique) at extracting phenolic compounds from 15 native plants, a greater inhibition capacity was obtained through UAE against three of the six bacteria studied: Listeria monocytogenes, Listeria innocua and Salmonella choleraesuis, whereas against the other three bacteria, S. aureus, Bacillus cereus and E. coli, the CE method proved to have a better antimicrobial capacity, therefore underlying the complex relationship between phenolic composition and biological activity.…”

Research Progress on Extraction and Detection Technologies of Flavonoid Compounds in Foods

“…At the optimized conditions, the MAE yielded a higher color density (68.63 ± 5.40), polyphenolic content (264.9 ± 10.025 mg GAE/100 mL), TFC (1662.22 ± 47.3 mg QE/L), and AOC (13.14 ± 1.05 µmol TE/mL) in a short time as compared to other methods. Saifullah et al [31] used MAE and RSM to optimize extraction parameters to maximize the extraction rate and antioxidant properties of phenolic compounds. Under optimal experimental conditions, MAE is eight times faster and requires six times less solvent than UAE and shaking water bath.…”

LC-ESI-QTOF-MS/MS Identification and Characterization of Phenolic Compounds from Leaves of Australian Myrtles and Their Antioxidant Activities

“…Though some studies are conducted on Australian myrtles [10,13,14], however, complete profiling of these plants is still lacking due to their complex nature and the unavailability of pure standards of phytochemicals. The emerging interest in the food supply required detailed analytical identification, characterization, and quantification of these pigments to understand their role in food and human health collectively.…”