The present invention encompasses a method of preparing a pharmaceutically active extract of D. Antarctica comprising the steps of:a. Collecting and disinfecting D. Antarctica plants；b. Exposing the D. Antarctica plants to ultra pure water at a temperature of from 95° to 100° C. for a period of about 5 hours to yield a liquid extract of the plant； andc. Lyophilizing the liquid extract yielding a dry homogeneous product.In another embodiment, the present invention provides an anti-aging pharmaceutical composition useful in slowing down or reversing the aging process in human beings said composition comprising an aqueous extract of D. Antarctica. In a particular embodiment the aqueous extract comprises a polyphenolic free-radical scavenger present in the amount of at least 4.0% (w/w) and preferably at least 5.0% (w/w)In another embodiment the present invention provides a method of treatment for the prevention of photoaging effects generated by exposure to harmful ultraviolet radiation comprising the step of administering to a human being a therapeutically effective amount of the aqueous extract of D. Antarctica. Preferably the extract is administered in the form of a cream, paste or gel
