The Bombay Stock Exchange benchmark Sensex today lost over 68 points in opening trade as funds and retail investors preferred to book profits amid weak Asian markets.The 30-share index, Sensex, declined by 68.60 points to 17,111 points. The wide-based National Stock Exchange index Nifty also slipped below the 5,100-points level and was quoted 19 points down at 5,084.