Extraction and Antioxidant Activities of Magnolia kwangsiensis Figlar & Noot. Leaf Polyphenols.

Microwave-assisted extraction was employed to extract polyphenols from the leaf of Magnolia kwangsiensis Figlar & Noot. The yield of polyphenols was 2.44±0.02 % under the optimal conditions of RSM: acetone concentration of 70 %, ratio of solvent to material of 21 mL⋅g-1 and extraction time of 16 min. The antioxidant activities were evaluated in terms of total antioxidant ability, reducing power, DPPH⋅ and ⋅ OH scavenging activity. Results showed the polyphenols presented potential antioxidant activities, especially the stronger scavenging activity on ⋅ OH. In term of ⋅ OH scavenging activity, the IC50 value of NKA-9 purification was 0.335 mg mL-1 , equivalent to 35.23 % of VC . The IC50 values of crude extract and ethyl acetate extract were 0.580 and 0.828 mg mL-1 , equivalent to 60.99 % and 87.07 % of VC . Results indicated that M. kwangsiensis leaf polyphenols present potential antioxidant activities that make it beneficial for human health by preventing or reducing oxidative damage.

Thermal stability and pathways for the oxidation of four 3-phenyl-2-propene compounds.

Cinnamaldehyde, cinnamyl alcohol, ß-methylstyrene and cinnamic acid are four important biomass 3-phenyl-2-propene compounds. In the field of perfume and organic synthesis, their thermal stability and oxidation pathways deserve attention. This paper reports a new attempt to investigate the thermal stability and reactivity by a custom-designed mini closed pressure vessel test (MCPVT). The pressure and temperature behaviors were measured by MCPVT under nitrogen and oxygen atmosphere. The temperature of initial oxygen absorption (T a) and rapid oxidation (T R) were calculated. The results showed that four 3-phenyl-2-propene compounds were stable under nitrogen atmosphere. The T a of cinnamaldehyde, cinnamyl alcohol, ß-methylstyrene, and cinnamic acid was 271.25 K, 292.375 K, 323.125 K, and 363.875 K, and their T R was 301.125 K, 332.75 K, 357.91 K, and 385.375 K, respectively. The oxidation reactivity order was derived to be cinnamaldehyde > cinnamyl alcohol > ß-methylstyrene > cinnamic acid. The oxidation kinetics were determined using n versus time (n-t) plots, which showed a second-order reaction. Peroxide was determined by iodimetry, and the oxidation products were analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that the peroxide value of cinnamaldehyde, cinnamyl alcohol, ß-methylstyrene, and cinnamic acid reached 18.88, 15.07, 9.62, and 4.24 mmol kg-1 at 373 K for 6 h, respectively. The common oxidation products of four 3-phenyl-2-propene compounds were benzaldehyde, benzoic acid, and epoxide, which resulted from the carbon-carbon double bond oxidation. The substituents' oxidation products were obtained from the oxidation of cinnamaldehyde, cinnamyl alcohol, and ß-methylstyrene. In particular, the difference is that no oxidation products of the carboxyl group of cinnamic acid were detected. The common oxidation products of the four 3-phenyl-2-propene compounds were benzaldehyde, benzoic acid, and epoxide, which resulted from the carbon-carbon double bond oxidation. The substituents' oxidation products were caught in the oxidation of cinnamaldehyde, cinnamyl alcohol, and ß-methylstyrene. In particular, the difference is that no oxidation products of the carboxyl group of cinnamic acid were detected. According to the complex oxidation products, important insights into the oxidation pathways were provided.

Characteristics and hazards of the cinnamaldehyde oxidation process.

Pressure and temperature behavior of the cinnamaldehyde oxidation process was determined using a custom-designed mini closed pressure vessel test (MCPVT), which is a new method to investigate the stability and hazard assesment of the cinnamaldehyde oxidation reaction. The oxidation products were analyzed by gas chromatography-mass spectrometry (GC-MS). The results showed that cinnamaldehyde was stable under nitrogen atmosphere but very unstable under oxygen atmosphere. The initial oxidation products were analyzed by iodimetry and the cinnamaldehyde peroxide value could reach 139.44 mmol kg-1 when the oxidation temperature was 308 K. The oxidation kinetics of cinnamaldehyde were studied by using the pressure versus time (P-t) curves obtained from the MCPVT process. The reaction is a second-order reaction, the kinetic equation is ln k = -2233.66 × (1/T) + 11.19, and the activation energy E a is 18.57 kJ mol-1 at 308-338 K. The explosion of the cinnamaldehyde oxidation reaction was observed by MCPVT, in which the onset temperature was 373 K. The main products of cinnamaldehyde oxidation are acetaldehyde, benzaldehyde, phenylacetaldehyde, acetophenone, 2-hydroxyphenyl acetone, cinnamaldehyde epoxide, benzoic acid, and cinnamic acid. Oxidation is a three-step process: (1) cinnamaldehyde reacts with oxygen to form peroxides; (2) complex oxidation reactions are caused by the thermal decomposition of peroxides; (3) rapid oxidation and thermal decomposition lead to explosion hazard.

Extraction of polysaccharides and its antitumor activity on Magnolia kwangsiensis Figlar & Noot.

The crude polysaccharides from the leaves of Magnolia kwangsiensis Figlar & Noot. were extracted by hot water extraction, the yield was 5.09%. Two polysaccharide fractions (P-2 and P-3) were isolated by DEAE-52 cellulose chromatography and Sephadex G-100 column chromatography in order, respectively. P-2 and P-3 were characterized by IR, HPGPC and GC-MS. P-2 was comprised of only glucose. Its molecular weight was 11.2×10(3) Da and the formula was C414H690O345. P-3 was comprised of xylose and rhamnose in the ratio of 1:4. Its molecular weight was 7.8×10(3)Da, and the formula was C319H528O220. The antitumor activities of P-2 and P-3 on the growth of human lung cancer (A549) cells and human gastric carcinoma (SGC7901) cells in vitro were evaluated. The results indicated that P-3 exhibited marked antitumor activities with IC50 value of 8.48 and 5.66 µg/mL.

Comparative analysis of essential oil composition from flower and leaf of Magnolia kwangsiensis Figlar & Noot.

The essential oils from Magnolia kwangsiensis Figlar & Noot. were obtained using hydrodistillation, and analysed by GC and GC-MS. A total of 31, 27 and 26 constituents were identified in the oils from male flower, female flower and leaf of M. kwangsiensis, and they comprised 99.2, 98.5 and 96.2% of the oils, respectively. Monoterpene hydrocarbons predominated in the oils and accounted for 48.3% of male flower oil, 54.0% of female flower oil and 44.6% of leaf oil. The compositions of flower oils were quite similar but with different content, and were different from those of leaf oil.