What does principle mean here?

Context:

The charges, if verified, seem unlikely to affect the field of resveratrol research itself, because Dr. Das’s work was peripheral to its central principles, several of which are in contention. “Today I had to look up who he is. His papers are mostly in specialty journals,” said David Sinclair, a leading resveratrol expert at the Harvard Medical School.

More:

http://www.nytimes.com/2012/01/12/science/fraud-charges-for-dipak-k-das-a-university-of-connecticut-researcher.html?_r=3&ref=science