For the result item returned by Google Desktop, try Getproperty on that
resultItem
rec.GetProperty("content"); // Where "rec" is the result item returned
of type IGoogleDesktopQueryResultItem
The list of properties you can query on a result item depends on the
type of item returned in the query. (im, file, web, ....). For the
exact properties supported by each metadata, look in the indexAPI
documentation.
You could also receive "No such property Name" error for the "optional"
parameters for each metadata listed in Index API documentation