export latest file to a variable

Dear experts,

I have some business requirement that the latest file should be exported to a variable 

Example: When we do ls -ltrh, then last file is the latest file i.e. lob_data01.dbf, so this file should be exported to a variable called latest_variable.

 [dbuser@dba2 testdb]$ ls -ltrh

total 4.6G

drwxr-x--- 2 dbuser dba 4.0K Nov 29 11:44 testdb

-rw-r----- 1 dbuser dba 101M Dec  3 04:07 users01.dbf

-rw-r----- 1 dbuser dba 501M Dec  3 04:07 retek_index06.dbf

-rw-r----- 1 dbuser dba 501M Dec  3 04:07 retek_index05.dbf

-rw-r----- 1 dbuser dba 501M Dec  3 04:07 retek_index04.dbf

-rw-r----- 1 dbuser dba 501M Dec  3 04:07 retek_index03.dbf

-rw-r----- 1 dbuser dba 501M Dec  3 04:07 retek_index02.dbf