Skin conditioner

A method of improving moisture retention ability of skin and/or treating or processing skin for another purpose, comprising applying to skin a composition containing one or more compound represented with the following formula (1):

• wherein R1 represents a hydroxyl group, lower alkoxy group that may optionally have a substituent, phosphoryloxy group, aryl group, amino group, sulfonic acid group, phosphatidyloxy group, lower alkyl group substituted with a hydroxyl group or amino group or lower alkyl group substituted with a guanidino group;
• R2, R3, R4 and R5 respectively and independently represent a hydrogen atom, lower alkyl group that may or may not be substituted with a hydroxyl group, aryl group that may or may not be substituted with a hydroxyl group, carboxyl group, or R4 and R5 represent groups that together form a carbonyl group with an adjacent carbon atom;
• and
• R6 and R7 respectively and independently represent a hydrogen atom, lower alkyl group that may or may not be substituted with a hydroxyl group, lower alkylcarbonyl group, aryl group, aralkyl group, or R6 and R2 represent alkylene groups, which may optionally have a substituent, that together form a five-member ring with an adjacent atom;
• and, nitrogen atoms in the formula may be in a quaternary form with a lower alkyl group.