A late 1970's to early 1980's B movie.?

There is a movie I saw as a kid that I think may have been on Showtime.that had a hero a lady in distressed he had to protect and of course a bad guy. The only thin I remember is the hero and lady somehow traveled to a weird planet or other dimension that was like prehistoric earth in a sense. The only other thing I remember at all about the movie was a strange fruit that grew on this tree that looked like a giant blueberry, black g, or plum, about the size of a cantaloupe at least. I think the hero ate one or it ended up in his face somehow but it was a mess.