In a 100-gram (3+1⁄2-ounce) serving, raw cucumber (with peel) is 95% water, provides 67 kilojoules (16 kilocalories) of food energy, and supplies low content of essential nutrients, as it is notable only for vitamin K at 16% of the Daily Value (table).
Depending on variety, cucumbers may have a mild melon aroma and flavor, in part resulting from unsaturated aldehydes, such as (E,Z)-nona-2,6-dienal, and the cis- and trans- isomers of 2-nonenal. The slightly bitter taste of cucumber rind results from cucurbitacins.
(Info: Wikipedia)