Abstract
In this study, the efficiency of microwave-assisted hydro-distillation (MAHD) to extract essential oil from Cinnamomum camphora leaf, and the recovery of polyphenols from extract fluid were investigated. The effects of microwave power, liquid-to-material ratio, and extraction time on the extraction efficiency were studied by a single factor test as well as the response surface methodology (RSM) based on the central composite design method. The optimal extraction conditions were a microwave power of 786.27 W, liquid-to-material ratio of 7.47:1 mL/g, and extraction time of 35.57 min. The yield of essential oil was 3.26 ± 0.05% (w/w), and the recovery of polyphenols was 4.97 ± 0.02 mg gallic acid equivalent/g dry weight under the optimal conditions. Furthermore, the comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) was used to characterize the essential oils of fresh and fallen leaves, and 159 individual compounds were tentatively identified, accounting for more than 89.68 and 87.88% of the total contents, respectively. The main ingredients include sabinene, l-β-pinene, β-myrcene, α-terpineol, 3-heptanone, and β-thujene, as well as δ-terpineol and 3-heptanone, which were first identified in C. camphora essential oil. In conclusion, the MAHD method could extract essential oil from C. camphora with high efficiency, and the polyphenols could be obtained from the extract fluid at the same time, improving the utilization of C. camphora leaf.
Highlights
The Cinnamomum camphora is known as an evergreen tree of Lauraceae, widely distributed in China and Japan [1]
With the increase of microwave power, the polarization of polar molecules caused by microwave is enhanced, and the heat motion of molecules as well as the cell rupture is promoted, thereby the output of essential oil is increased [29]
Excessive microwave power may lead to the decomposition of some thermo-sensitive metabolites, which affects the essential oil yield [18]
Summary
The Cinnamomum camphora is known as an evergreen tree of Lauraceae, widely distributed in China and Japan [1]. Some studies indicated that the extract of C. camphora leaf and its bioactive components have antioxidant, anti-inflammatory, antialgal, antimicrobial, and insecticidal. The antimicrobial activity of C. camphora essential oil has received wide attention, such as the antibacterial activity against Bacillus subtilis, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella gallinarum, as well as the antifungal effect against Alternaria solani Sorauer, Gacumanomyces graminis, and Choanephora cucurbitarum [11,12,13,14,15]. The essential oils of C. camphora have high insecticidal and repellent activities against Anopheles stephensi, Aphis gossypii, Tribolium castaneum, and Lasioderma serricorne [9,16]
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