laevo- In the US, levo-. Also l- and L-.
On or to the left.
[Latin laevus, left.]
Many chemical compounds rotate polarized light to the left (that is, anticlockwise facing the oncoming radiation) and are then said to be laevorotatory. A number of compounds include laevo- or levo- in their names to indicate they are laevorotatory, for example laevulose (another name for the sugar fructose), the antibiotic levofloxacin, and levodopa, used in the treatment of Parkinson's disease. In chemical names, the laevorotatory form is sometimes indicated by l-. The optical activity of a compound reflects the arrangement of the atoms in its molecules; the prefix L- has been used to refer to one whose shape is consistent with that of L-glyceraldehyde; for example, levodopa is usually abbreviated to L-dopa. However, l- forms are not necessarily also L- forms and both prefixes have largely been replaced by other naming conventions. The opposite to laevo- is dextro-.