Absolutely! You just have to demonstrate an interest in research and a thorough understanding of the work you've done. I have supervised quite a few UGs, and I am always amazed how little they care about the actual work. To them, this is just another thing to add onto their resumes. At an interview, I spoke with an applicant who talked endlessly about his research. It didn't take much to realize that he was using buzz words, and he actually had very little knowledge of what exactly his research problem was. So, as long as you can discuss intelligently and casually what your research was about both in your application and in an interview, you're fine. Having no publications is no big deal. A good MD/PhD program understands the rigors of research. It ain't easy to publish - not in one year of 10 hours a week, which is the average time a UG can commit.
If you are concerned that your research was not involved enough, you might want to consider taking a year off and working in a start-up lab i.e. a young, untenured faculty's lab. These sort of labs are ambitious, understaffed and will give you maximum exposure. The only down side is that the PI is often unknown.
More you have better it is. Just remember to be able to discuss your work when you are at the interview. Make sure you know back ground and important info to show that you really understood what you were doing.