How to create alphabetised data validation from an array and ignore items ending with a period?

I have a spreadsheet like this:

Trip 1    Person 3    Person 2    Person 5

Trip 2    Person 2    Person 4.    Person 1   

Trip 3    Person 1    Person 3.    

Trip 4    Person 1    Person 2     Person 7

Trip 5    Person 6

Trip 6    Person 2.    Person 7.

             Highlight:  (Data Validation)

How can I make the drop-down list alphabetised and ignore the items ending in full stops?