Components Analysis Of Black Peanut Skin Pigment And Its Effect On Reducing Blood Lipid

Black peanut skin pigment (BPSP) is a natural plant melanin, which is extracted from the peanut processing industry by-products, peanut skin. Response surface method (RSM) is applied to optimize the ultrasonic extraction of flavonoids from black peanut skin, taking the flavonoids extraction rate as reference standard. The process condition of macroporous resin purification of BPSP is determined by comparing the adsorption and desorption with different kinds of macroporous resin. The stability of BPSP under different environment conditions is investigated by change of the structure and color. The compositions of pigments in black and red peanut skins are preliminarily identified with special chemical reaction of organics and UV-visible spectrophotometry. The compositions of anthocyanins and proanthocyanidins in black and red pigment of peanut skins are investigated by high performance liquid chromatography-mass spectrometry(HPLC-MS). Effects of free radical scavenging and lipid-lowering of proanthocyanidins from black peanut skin are studied in this paper. The main results are as following:1. Response surface method(RSM) is applied to optimize the ultrasonic extraction of flavonoids from black peanut skins. The results show that alchohol concentration, ultrasonic power and ultrasonic temperature are key factors to the extraction of flavonoids and the optimal conditions for the extraction are as follows:ratio of material to solvent(1:60), ultrasonic time (4min), alcohol concentration(59%), ultrasonic power(200W) and ultrasonic temperature(34℃). With the optimum extraction conditions, the extraction yield of flavonoids from black peanut skins is 5.433%.2. The optimal technological parameters of the separation and purification process of BPSP is as following:the AB-8 macroporous resin has the best separating efficiency under the following technological conditions:the work solution concentration is 2.0mg/mL; the absorption velocity is 1.5mL/min; the maximum absorption capacity of BPSP is 4 times to the macroporous resin of volume; the volume of distilled water is 5 times to the volume of macroporous resin; the concertration of ethanol is 70%(4 times to the volume of macroporous resin). The content of flavonoids in BPSP has increased from 20.96% to 36.28%.3. The results indicate that BPSP is unstable to light and heat while it shows good stability to sugar, salt and preservatives. And the color becomes deeper when added vitamin C. BPSP is adapted to broad pH, and we can obtain different colors by chancing the pH. It is unstable to oxidizing agent and reducing agent. It also demonstrates good stability towards several metal ions except for Cu2+ and Fe2+, which makes BPSP produce precipitation. The color of BPSB is natural, so it is a very potential natural melanin. When using it, avoid light and forbid mixing with oxidizing agent, reducing agent, Cu2+ and Fe2+.4. The compositions of pigments are qualitatively analyzed by special chemical reaction of organics and UV-visible spectrophotometry. The results show that the compositions of BPSP are mainly anthocyanins and proanthocyanidins, and the contents are 9.39% and 16.62%, respectively. The proanthocyanidins is found in red peanut skin pigment (RPSP), and the content is 24.51%, anthocyanin is not detected.5. The compositions of black and red peanut skin pigment are qualitatively analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS). As a result,22 and 9 anthocyanins compositions are identified in black and red peanut skin, there are 5 same anthocyanins compositions in the two kinds of peanut skins. There are 4 dimmers and 4 trimers of proanthocyanidins are identified in red peanut skins, and 3 dimmers and 4 trimers in black peanut skins.6. Proanthocyanidins from black peanut skin has scavenging activities to hydroxyl radical and superoxide anion radical, it is an excellent natural antioxidant. The total triglycerides, total cholesterol and low-density lipoprotein cholesterol concentration of serum in mice fed with proanthocyanidins from black peanut skin are significantly lower than those in hyperlipemia model group, while serum high-density lipoprotein cholesterol concenteation is higher. Comparing with hyperlipemia model group, the activities of lipoprotein lipase and hepatic lipase in mice liver are significantly increased. The results show that, proanthocyanidins from black peanut skin can reduce blood lipid levels in hyperlipidemic mice and regulate lipid metabolism.