SEVERE TURB CAUSED PAX INJURIES AND ACFT CABIN DAMAGE TO ACR LTT TURBO PROP DURING CRUISE.

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WE WERE IN LEVEL CRUISE AT FL230 APPROX 85 MI SW OF RAZORBACK VOR. FLOW CTL HAD RERTED US ON A W TO NW DEP FOR A NE DEST. THERE WAS A HUGE CELL OVER MCALESTER VOR N OF DALLAS THAT HAD SPAWNED SOME RPTED TORNADOES. OUR RADAR WAS FUNCTIONAL AND WE WERE WELL CLR OF THE CELLS IN THE AREA. IN THE CLR AS WE WERE ABOUT TO LEAVE AN AREA THAT LOOKED LIKE IT WAS UNSTABLE; THE ACFT WAS HIT BY A SEVERE JOLT OF APPROX 2 SECOND DURATION. I ESTIMATE WE PULLED A MOMENTARY (1/2) POSITIVE G FOLLOWED BY A (1) NEGATIVE G. NOTHING BEFORE OR AFTER. FLT ATTENDANT CALLED UP TO THE COCKPIT AND SAID SEVERAL PAX HAD HIT THEIR HEADS ON THE CEILING AND THERE WERE SOME PANELS FALLING DOWN. WE CALLED AHEAD AND REQUESTED MEDICAL ASSISTANCE AND A MECH TO MEET US UPON OUR ARR AT FYV. REST OF FLT AND LNDG WAS UNEVENTFUL. ONE PAX COMPLAINED OF NECK PAINS AND SHE WAS TAKEN TO A HOSPITAL WHERE X-RAYS WERE TAKEN. SHE WAS LATER RELEASED. THE SEAT BELT SIGN HAD BEEN ON THE ENTIRE FLT AND THE FLT ATTENDANT HAD JUST DONE A COMPLIANCE CHK. IN MY REVIEW OF ACTIONS THAT WERE TAKEN; I CAN'T SEE ANYTHING THAT WE COULD HAVE DONE TO AVOID THE SIT; WITH THE EXCEPTION OF NOT FLYING ON A DAY WHEN THE CONVECTIVE ACTIVITY WAS HIGH.