If you are well. hydrated it can help to prevent constipation.
Good source of fiber. which with fluid helps constipation.
Laxative effect. Prune juice is a well known laxative. It is not completely clear why Sorbitol, a sugar in it may be part of the reason, as it can cause water to be absorbed into the intestine, which softens the stool, Dried prunes are even better for you because they have a lot of fiber which helps with constipation among other things. I think dried prunes are delicious! See: http://tinyurl.com/ktqm2ng.
Keeps you regular. Many people find that daily prune juice promotes regular bowel movements. The same may be accomplished by apricot juice. Increasing dietary fiber (e.g., granola for breakfast) may help too. A person who has a sudden persistent change in bowel habits, however, should consult a physician.
Differ. Can help some with constipation.