Just wanted to throw in a few definitions: astringent isn’t a flavor. It’s a bodily reaction to chemicals. If your tissues constrict in response, it’s astringent. Bitter and sour are flavors.
If you feel it in your soft tissue, it’s acidic or astringent; if it’s a tongue reaction, it’s bitter or sour. If it’s both and pleasant we call it tart, and if it’s both and unpleasant we call it toxic or caustic or inedible.
edit Incidentally, biologically, sour flavors are associated with potential danger from decomposition while bitter flavors warn of potential heavy metal contamination.