Extraction And Preparation Aloin And Aloe-emodin From Aloe Powder

The aloe is a kind of medicine plant with higher economic value, widely cultivated in china. However, the processing technique is backward. As main functional components of aloe, aloin and aloe-emodin are widely used in medicine, health care products, cosmetic industry. Research on preparing aloin and aloe-emodincan will provide scientific reference and technique support for aloe products exploitation, which is very significant to the development of aloe industry.In this paper, we firstly established the HPLC analysis method of aloin and aloe-emodin. The aloin was measured by HPLC using eclipse XDB-C18 column (4.6 mm×250 mm, 5μm) with the solution of 55 % methanol +45 % water as eluant at 0.8 mL/min.The eluate was measured at 354nm and room temperature; The aloe-emodin was measured by HPLC using eclipse XDB-C18 column (4.6 mm×250 mm, 5μm) with the solution of 80% methanol + 20% water as eluant at 0.8 mL/min.The eluate was measured at 254 nm and room temperature. The measured concentrations of aloin and aloe-emodin in aloe powder would provide reference for the follow-up experiments.The extraction of aloin with ethyl acetate was optimized by orthogonal experiment to study the effects of extracting temperature, extracting time, extracting reagent volume and extracting times. The optimum extraction condition was as followings: to 14g aloe powder, extracting temperature, extracting time, extracting reagent volume and extracting times were 57℃, 30 min, 300 mL and 4 respectively. The extraction ratio was 77.15%. Then crude extracts were dissolved in isobutyl alcohol, and kept it for 24 h at -5℃. The 80.73 % aloin crystallizes were collected by filtration, and recovery ratio was 51.35 %. The 80.73% aloin crystal was dissolved in water, 93.5% aloin crystal was obtained by stirring for 30 min at room temperature, filtering and drying.The effects of time, temperature, pH and metallic ions on the stability of alion aqueous solution were investigated by HPLC method. The results indicated that aloin dissolved in water was unstable, the degradation ratio reached 90.5% at room temperature in 6 days. Temperature and pH had remarkable influences on the stability of alion. At 80℃, the degradation ratio could reach 98% in 8 hours. But the ratio was less than 5% at 5℃in 4 days. At pH≥7.0, the degradation ratio was more than 95% in 12 hours, while the ratio was only 21.1% at pH2.0 in 4 days. Mn2+,Cu2+ and Fe3+ could increase the aloin degradation, while Mg2+ could decrease the aloin degradation.In this paper, we designed a meathod for preparing aloe-emodin from aloe powder by oxidizing aloin with FeCl3. Aloe powder was added into hydrochloric acid solution, refluxing for 30min at 106℃, separating the liquid from the sediment by filtration,and then adding FeCl3 solution to the filtrate and keeping it for 8 h at 106℃. Under these conditions, the conversion ratio of aloin to aloe-emodin was 89.15 %. Toluene was used in extraction of aloe-emodin. 95.59 % aloe-emodin was obtained by crystallizing at -5℃, filtering and drying.