If adult content in the sample is a problem, then I have got some big issues to deal with. 
(That said, no, it's no problem. This is a site that allows dubcon and pseudo-incest, so...)
If you really want to put a warning in your blurb, than a simple "This book contains adult language and situations" usually suffices. You can be as specific as you want if it includes sexual situations too, and to what degree. Usually a nice way of saying it is "This book is for mature audiences."
Of course, no matter what you do, you will probably get reviews saying it's too crude/sexual/whatever. I don't worry about those too much since those are reviews that help sell your work.
(That said, no, it's no problem. This is a site that allows dubcon and pseudo-incest, so...)
If you really want to put a warning in your blurb, than a simple "This book contains adult language and situations" usually suffices. You can be as specific as you want if it includes sexual situations too, and to what degree. Usually a nice way of saying it is "This book is for mature audiences."
Of course, no matter what you do, you will probably get reviews saying it's too crude/sexual/whatever. I don't worry about those too much since those are reviews that help sell your work.