Antioxidant And Hypoglycemic Effects Of Adinandra Nitida Extracts In Vitro And In Vivo

Diabetes mellitus (DM) is a metabolic disorder in the endocrine system. The disease is found in all parts of the world and is rapidly increasing in most parts of the world. It is one of the most serious diseases that affect human health with a high prevalence of morbidity and complication at present. Along with the development of DM, continuous high blood glucose can cause many serious complications such as ketoacidosis nephropathy, cardiopathy and retinopathy. The researches have found that the reactive oxygen species (ROS) played an important role in the development an progess of diabetic complications.Flavonoids, which exist ubiquitously in fruits, tea, vegetables, and medicinal plants, have been studied extensively and received great attention, since they are effective free radical scavengers and are assumed to be less toxic than synthetic antioxidants. The studies have found that flavonoids is a kind of main active components in natural medicinal plants with many physiological functions such as antioxidative and antibacterial activities, these researches have shown that flavonids have many potential medicinal values too.Adinandra nitida Merr. ex H.L. Li (Theaceae), a wild plant in south China, is a flavonoid-rich plant. Its leaves have been consumed as a health tea (Shiyacha) and herbal medicine for hundreds of years. It is reported to have many curative effects such as reducing blood pressure, as well as antibacterial, antioxidant, and analgesic properties. The total flavonoid content in A. nitida leaves was more than20%with camellianin A as the main flavonoid. Today, A. nitida has been cultivated in Guangxi province, China, so there is the possibility of large-scale application of flavonoids from A. nitida leaves in functional food and medicine. However, so far, A. nitida leaves have not been completely studied. There are few reports on the study of A. nitida leaves in treating DM and its complacations. The experiments based on HepG2cells, a-glycosidase and (STZ)-induced diabetic rats pattern was carried out, in order to research and evaluate the effect in treating diabetes mellitus and its complications of Adinandra nitida. The main content was summarized as follows:1. Chemical analysis on diffenrent polar parts of Adinandra nitida leavesFractions with different polarity from the ethanol extract of Adinandra nitida leaves were prepared by slovent extraction. Acetic ether fraction which was rich in total phenois and the content is about367.9mg/g. N-buthanol fraction which was rich in flavonoids and the Camellianin A level is about433.87mg/g. Using column chromatography mothod in exacting and separating the fraction of ethyl acetate and normal butanol,we weap two substance, Camellianin A and Apigenin.2. To evaluate the anti radical activity of different fractions in vitroDPPH, ABTS and cellular assay were carried out to evaluate antioxidant activity of different fractions. Both in vitro antioxidant activity test and HepG2cells-based assay showed that acetic ether fraction and the n-buthanol fraction had the highest antioxidant activity.3. Hypoglycemic effects of selected sub-fractions on (STZ)-induced diabetic ratsIn long-term therapy test in (STZ)-induced diabetic rats, acetic ether fraction and n-buthanol fraction had positive effect in the treatment of (STZ)-induced diabetic rats. Compared with the diabetic control group, groups were given these fractions to increase superoxide dismutase (SOD) and catalase (CAT) activity and decrease malodialdehyde (MDA) level in rats plasma. Meanwhile, they had lower plasma glucose (FBG). Adinandra nitida, especially the acetic ether fraction and n-buthanol fraction showed the ability of treating diabetes and its complications by prevent the decrease in SOD and CAT activity and suppress the increase of MDA.4. Preliminary study on hypoglycemic mechanism of selected sub-fractionsThe a-glycosidase was used to analysis the inhibition of a-glycosidase activity. HepG2cells were used to evaluate the ability of fractions to enhance glucose uptake. Acetic ether fraction and n-buthanol fraction showed no ability on the inhibition of a-glycosidase activity and enhancing glucose uptake in HepG2cells. A tentative inference on this result is that Adinandra nitida can effectively repair the impaired islet cells, and accelerate the insulin discharge, it can inhibit the hyperglycaemia secretion, and decrease the generation of hepatic glycogen. As a consequence, the two fractions play an active role in treating (STZ)-induced diabetic rats.