Extraction optimization, preliminary characterization, and in vitro antioxidant activities of crude polysaccharides from finger citron

Finger citron (Citrus medica L var. sarcodactylis) (FC) fruits, widely cultivated in the southern provinces of China, have been long used as traditional Chinese medicinal material. Response surface methodology was used to optimize the extraction conditions of crude polysaccharides (FCPs) from FC fruits with a central composite design. Three independent variables such as extraction temperature (degrees C), extraction time (h), and ratio of water to raw material were investigated. The experimental data obtained were fitted to a second-order polynomial equation using multiple regression analysis. The 3-D response surface plot and the contour plot derived from the mathematical models were applied to determine the optimal conditions. The optimum conditions were as follows: extraction temperature 100 degrees C, extraction time 1.5 h, and ratio of water to raw material 40. Under these conditions, the experimental value was 3.19 +/- 0.10%, which is well in close agreement with value predicted by the model. Fourier transform infrared spectrometry spectra revealed the general characteristic absorption peaks of FCPs. Then, we demonstrated that FCPs had strong scavenging activities in vitro on DPPH, hydroxyl and superoxide anion radicals. Overall, FCPs may have potential applications in the medical and food industries. (C) 2012 Elsevier B.V. All rights reserved.