TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The pretreatment step of the medicinal material comprises before slicing the fresh Rehmannia root tuber into sheets or pieces, optionally peeling off; and optionally removing the parts except the white and light yellow heart of the middle part of fresh Rehmannia. In addition to active carbon column chromatography method, solvent extraction method, silica column chromatography method, and/or crystallization method can be used for preparing the catalpol product with different purities. The concentrating method comprises thin film evaporation at normal pressure or reduced pressure condition, rotary evaporation, and extraction-concentration. The drying method comprises vacuum drying, spray drying, and freeze drying. The extracting conditions comprise adding calcium carbonate or barium hydroxide in the raw material, and heating under oxygen-free condition for restraining the activity of enzyme and neutralizing the vegetable acid; or directly thermally processing with water steam without inactivation, and directly extracting. The solvent in solvent extraction step is water, alcohol, and/or ketone. The extraction method can be breaking extracting, soaking, infiltrating, reflux extracting, continuous reflux extracting, ultrasonic extracting, microwave-assisted extracting, and enzymatic extracting. The active carbon column chromatography comprises using coal active carbon, wood active carbon, bamboo based active carbon, or shell active carbon (preferably coconut shell active carbon), where active carbon is in powder or preferably granular form; using compression adsorption, decompression adsorption, low-temperature adsorption, or high-temperature adsorption; eluting at normal pressure, where concentration of sample liquid is 0.05-1.0 g/ml, the adsorption flow rate is 1-6 bed volume (BV)/hour, and the resin column diameter height ratio is 1:5-1:20; washing with water to remove impurity, where impurity removing flow rate is 1-6 BV/hour; and analyzing using solvents, such as 10-100% methanol, which is 2-6 times the column BV, ethanol, or acetone, and analysis flow rate is 1-6 BV/hour. The silica column chromatography comprises using dry column method or wet column method, where eluent is mixed solvent comprising water, methanol, ethanol, acetone, ethyl acetate, and trichloromethane. The crystallizing solvent is water, methanol, ethanol, acetone, ethyl acetate, and/or trichloromethane (preferably acetone-water system). Crystallization can be cooling crystallization, evaporation-crystallization, vacuum crystallization, reaction and salting-out crystallization, supercritical crystallization, physical field reinforced solution crystallization, film crystallization, and compression crystallization.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The filtering of extracting solution comprises centrifuging, ultrafiltering, and filter pressing, where clarifying agent is optionally used, such as alcohol precipitation agent, resins, 101 fruit juice clarifying agent, chitin (e.g. chitosan), ZTC natural clarifying agent, gelatin, and/or tannic acid.