Extraction, Purification And Chelation Of Naringin

As one of flavanones and mainly present in the peels and fruits of pummelo, grapefruit, sour orange and their hybrids, naringin has been proven to have various biological activities such as preventing cancer, inhibiting the growth of microbes and the activities of many enzymes, antioxidating, lowering the levels of blood cholesterol and triglyceride and maintaining the normal permeability of blood capillary. Because of this, naringin can be used in fields of medicine and food.In this dissertation, six major investigations have been done. Firstly, orthogonal experiment was used to optimize the ethanol extraction conditions of narigin from pummelo albedo. It had been found that the extraction rate was up to 3.38 when dried peel was soaked in 70% ethanol water solution 25 times as much as the weight of the peel for 1 hour at 60 ℃.Secondly, a systemic investigation on the static adsorption and desorption of two resins DM130 and D140 on naringin was also performed. The results had showed that DM130 was super to D140 both in the amount and speed of adsorption for naringin while it had lower desorption ability compared to D140. The static adsorption values of DM130 and D140 for naringin were 130.87mg/g and 108.03mg/g, and the time to reach the adsorption balance was 6 hours and 8 hours, respectively. 90% ethanol water solution was proved to be an effective desorptive agent for naringin absorbed with their desorptive rates being 90.76% and 93.34%, respectively. Besides, the resin DM130 and a modified 3-step crystallizationmethod were used to purify naringin extract. The latter method had a higher purity (90.01%) but a lower yield (2.65%) of naringin compared with the resin method, these two values by the resin method being 85.07% and 3.76%, respectively. This indicates that naringin with much higher purity cannot be gained using only one of these two methods.Thirdly, it is the first time to do a systemic study on the chelation of naringin with metal ions. The results are as follows: (1) Naringin was chelated with six metal salts in different mole ratios. The optimum mole ratio of naringin to copper nitrate or copper acetate was 2 to 1, and the mole ratio of naringin to zinc nitrate, zinc acetate, aluminium chloride or ferric chloride was 1 to 1. (2) The optimum chelation conditions for naringin with these six salts were different. The optimum solution pH values, reaction time and temperature for 0.005 mol/L naringin to chelate with 0.005 mol/L copper nitrate and copper acetate were 8.55 and 9.06, 35 minutes and 30 minutes, 45 ℃ and 25 ℃, respectively. The chelation action was the highest when 0.005 mol/L naringin was reacted with 0.005 mol/L zinc nitrate and zinc acetate under the following conditions with the solution pH values being 9.48 and 10.06, 45 minutes and 30 minutes, and 45 ℃ and 35℃, respectively. When 0.005 mol/L naringin was reacted with 0.005 mol/L aluminium chloride or ferric chloride in the solution pH value of 8.50 for 45 minutes at 45℃, the chelation reaction was the most complete. (3) The yields (%) of six narigin complexes with copper nitrate, copper acetate, zinc nitrate, zinc acetate, aluminium chloride and ferric chloride named as complexes 1 to 6 in that order were 76.09, 76.50, 59.55, 60.24, 58.47 and 64.56, respectively. This showed that naringin was more easy to chelate with copper salts and less easy with aluminium salt. (4) The UV and IR analysis for the six naringin-metal complexes indicated that the chelating groups in naringin were 4-carbonyl and 5-hydroxyl. There showed good consistence in between the analytic and theoretic data for the contents of three elements (carbon, hydrogen and metal) and water in the complexes. The possible structures and molecular formulas for the six complexes were derived from the above data. (5) Inthese six complexes, the melting points of two naringin-copper complexes had been detected as 238.0℃ and 237.7℃, respectively, while the remaining four naringin-metal complexes had no detectable melting points. (6) The start temperature...