| Diabetes has been considered as chronic lifelong disease which seriously affected on human's health, one of main threatens to people's health since the beginning of twenty-first century. According to statistics, three percent population in the world were affected diabetes, what's more, over ninety percent of diabetic patients suffered from type 2 diabetes, which is noninsulin-dependent diabetes mellitus. It's expected that the number of diabetic will have exceeded 0.3 billion by the year of 2025. Diabetes, which is a serious disease of disturbance of endocrine metabolism, is caused by deficiency of insulin metabolism. It leads to a series of complications, such as cardia-cerebrovascular disease, oculopathy, degenerative nephritis, nervous disorders and so on. What's worse, these complications may result in amputation, acroisa and even death. As one of the ten "killers" in Asia, the extent of epidemic of diabetes has exceeded infectious diseases. PAUL AIMMER, chairman of International Research Institute on Diabetes, affirmed that with the deterioration of diabetes may have more detriment than acquired immune deficiency syndrome (AIDS).Therefore, precaution and cure of diabetes is imminent.The common characters are hyperglycaemia and complications caused by long-term hyperglycaemia. It's convincingly proved by recent epidemic research and clinical experiment that hyperglycaemia is primary cause of the complications of diabetes. The advances of the research on complications of diabetes showed that the four mechanisms of pathopoiesis have the same process induced by hyperglycaemia, that is, excess of chondriosome electron transfer chain superoxide. Therefore, to effectively control blood glucose is the criticality of precaution and cure for diabetes complications. Reducing blood glucose perhaps will reduce the danger rate of complication of capillary vessel system disease, and complication of great vessel is most likely to be avoided.Coffee is one of the biggest consumption of drink all over the world and becomes increasingly popular. Caffeine and chlorogenic acid are the main component. A lot of further researches on pharmacological activity of coffee have been performed recently. The results showed that caffeine in coffee has effect on inhibiting absorption of and reducing fat, besides nerve stimulation action as we known. Chlorogenic acid in coffee, a substance which has physiological activity, is closely related to human's health. It has various pharmacologicalactions, such as cholagogue, antibiosis, antianaphylaxis, anti-teratogenic, increasing leucocyte, antioxidation, cleaning DPPH free radical in the body, anti-AIDS, precaution of cardiovascular disease, diabetes and some kinds of cancers. It's reported by Yoshioka K that coffee can inhibit not only the accumulation of fat in the body, but also the increase of blood glucose concentration. Besides regulating strenuous living, Coffee may contribute to losing weight and curing diabetes as an auxiliary substance, but the active component was indefinite. Consequently, to isolate caffeine and chlorogenic acid by consciously and purposely and illuminate the action of reduce blood glucose by vitro and vivo experiments and identify active component are main objectives of the experiment.Two monomers were extracted and isolated in the experiment. By physical and chemical identification, ultraviolet spectrum(UV), infrared spectrum(IR), mass spectrum(MS), high performance liquid chromatography(HPLC), they are identified as caffeine and chlorogenic acid, respectively.An HPLC method for the determination of caffeine and chlorogenic acid in coffee was established. The RP-HPLC method was applied. The analytical column was ZORBAX SB-C18 column (150mm x 4.6mm, 5um). For caffeine, the mobile phase was acetic acid buffer solution. The flow rate was 0.8mL-min-l and the UV detection was set at 254nm. For chlorogenic acid, methanol-citric acid buffer solution was adopted as the mobile phase, the proportion was ranged from 20 '. 80 to 50 : 50. The flow rate was 0.5 mL-min"1 and the UV detection was set at 325nm. Caffeine showed good linearity (r = 0.99973) in the range of 0.05~0.80mg?mL''. The average recovery (n = 6) was 99.28% (RSD = 0.7%); chlorogenic acid showed good linearity (r = 0.99903) in the range of 0.04~0.64mg?mL~'. The average recovery (n = 6) was 99.39% (RSD = 0.7%). The method is accurate and reliable, suitable for the determination of caffeine and chlorogenic acid in coffee. The relevant data for the further study on the antiobesity and antidiabetes effects of coffee was provided in this experiment.The inhibitory effect of the hot-water extraction from coffee on the postprandial blood glucose concentration in rats in pharmacological experiment was determined. The inhibitory effects of the hot-water extraction of coffee seeds in Kud: Wistar rats were performed by oral saccharide tolerance test (OST) in vivo, while the suppression on a-amylase and a-glucosidase activity in vitro. The results showed that the hot-water extraction of coffee seeds significantly inhibited the activities of a-amylase and a-glucosidase, and reduced the postprandial blood glucose concentration by OST. The same as acarbose, chlorogenic acidinhibited strongly the activity of a-glucosidase and also reduced the postprandial blood glucose concentration by OST. But caffeine, which is a major component of coffee seeds, had no such effect. It's revealed that the inhibitory effect of the hot-water extraction of coffee seeds on postprandial hyperglycemia may be due to inhibition of a-glucosidase by the chlorogenic acid, which is a major component of coffee.
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