Abstract: The present invention provides a dehydrogenase mutant L283V/L286V, and a preparation method and use thereof, and relates to the field of biomedicine technologies. An amino acid sequence of the mutant L283V/L286V is as shown in SEQ ID NO: 1; and the mutant is prepared by simultaneously mutating 283rd and 286th leucine of a dehydrogenase with an amino acid sequence as shown in SEQ ID NO: 3 into valine. The dehydrogenase mutant L283V/L286V shows high selectivity in catalyzing myosmine reduction reaction in a whole cell system to produce S-nornicotine, and has relatively high dehydrogenase and imine reductase activities, a short enzyme reduction time, and a high transformation rate. The product S-nornicotine obtained through the reaction has extremely high optical purity, which reduces the operation difficulty of subsequent purification.

Abstract: An icariside compound as shown in Formula I wherein the compound is a natural chemical component in the traditional Chinese herbal epimedium or a chemically modified or a totally synthetic product based on the natural component. The compound can be used for preparing pharmaceuticals, health care products, cosmetic and skin care products and the like for improvement of immunity in a human body.