Optimization of Extraction and Purification Process of Total Phenols from Deoiled Cinnamomum Longepaniculatum Leaves and Its Antioxidant Study in Vitro

OBJECTIVE  To explore the optimal process of extraction and purification of total phenols from deoiled Cinnamomum longepaniculatum leaves, and to evaluate the antioxidant activity in vitro before and after purification, so as to provide a theoretical basis for rational development and utilization of Cinnamomum longepaniculatum.

METHODS  The L₁₈(3⁷) orthogonal experiment was carried out on the basis of five-single factor and three-level experiments, such as concentration of ethanol(A), ratio of liquid-material(B), extraction temperature(C), extraction time(D), and extraction times(E). The extraction process of total phenols was optimized, by taking the amount of total phenols extraction as the process investigation index. Taking the adsorption and desorption performance under dynamic and static conditions as the investigation index of total phenols purification process, the purification process of total phenols was optimized by macroporous resin. With vitamin C(Vc) as the positive control, the antioxidant activity in vitro of total phenols before and after purification were evaluated by DPPH radical scavenging, ABTS⁺ radical scavenging and determination of total reducing capacity.

RESULTS The best extraction technology conditions of total phenols were as follows: ratio of liquid-material 30 mL·g⁻¹, concentration of ethanol 50%, extraction time 2 h, extraction temperature 90 ℃, extraction 2 times. Under such conditions , the extraction amount of total phenols from deoiled Cinnamomum longepaniculatum leaves was 15.63 mL·g⁻¹. HPD-600 type macroporous resin showed the best purifying profile. The best purification technology conditions were as follows: the concentration of sample solution was 0.5 g·L⁻¹, the sample solution pH value was 3, the sample volume was 2.5 BV, the sample flow rate 1 mL·min⁻¹, the impurity was removed by 4.5 BV distilled water, the elution concentration of ethanol was 60%, the eluate pH value 7, the elution flow rate 1 mL·min⁻¹, 4.5 BV eluent was collected and the total phenols assay was increased from 12.51% to 26.40%. The purified total phenols showed excellent antioxidant activity in vitro. The scavenging effect of total phenols after purification on DPPH and ABTS⁺ free radicals increased with the increase of total phenols concentration. The IC₅₀ values of DPPH radical scavenging activity of total phenols before and after purification were (68.31±1.96)mg·L⁻¹ and (38.07±0.66)mg·L⁻¹, respectively. The IC₅₀ values of ABTS⁺ radical scavenging activity of total phenols before and after purification were (23.88±1.66)mg·L⁻¹and (14.28±0.19)mg·L⁻¹, respectively. The absorbance values of the total reducing capacity of total phenols was 1.68 times higher than that before purification. The scavenging effect of total phenols before and after purification on DPPH, ABTS⁺ free radical scavenging and total reducing capacity was weaker than that of Vc.

CONCLUSION The process is stable and feasible, suitable for industrial production, and has the advantages of simplicity, rapidity and accuracy, which lays a foundation for further research on Cinnamomum longepaniculatum and the development of natural antioxidants.