You might checkout this web site to see if it will help:
Markdown Services
This is a set of OS X services that contain the following commands:
- Markdown to HTML: Replaces selected text written in Markdown with the corresponding HTML.
- HTML to Markdown: The reverse of the previous: replaces selected HTML with the corresponding Markdown.
- Copy Markdown as RTF: Copies the selected Markdown text to the clipboard as rich text, suitable for pasting into TextEdit or a word processor.
- Paste as Markdown: The reverse of the previous: converts rich text on the clipboard into Markdown and pastes it into a document.