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.
Highlights
Phenolic compounds are non-nutritive phytochemical groups synthesized in the plant as secondary metabolites
Our results reveal that higher sample to solvent ratios have lower extraction yields of phenolic
Our findings show that the linear effect of radiation time, microwave quently releasing more phenolic compounds [47]
Summary
Phenolic compounds are non-nutritive phytochemical groups synthesized in the plant as secondary metabolites. Despite the lack of nutritional attributes, they have been widely used as natural antioxidants and antimicrobial agents in foods [1,2]. They have been used as supplements or therapeutic agents for prevention and/or delay several health complications such as cancer, diabetes, neurodegeneration, early aging, inflammation, hypertension, allergies, arthritis, and cardiovascular diseases [3,4,5]. Polyphenols derived from lemon myrtle leaves have various bioactivities such as anti-inflammation [8,9], antimicrobial [10,11], cytoprotective, and pro-apoptotic properties [12]. To meet the demand it has been growing commercially in different parts of the world, though it is native to the Australian coastal rainforest of Queensland and New
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