Snapping a four-day gaining streak,the BSE benchmark Sensex declined by 51 points in early trade today as funds and retail investors booked profits after recent rally amid a mixed trend in the Asian region.The 30-share barometer declined by 51.21 points, to 19,355.64, led by the weakness in bank, auto and capital goods stocks. The index had gained almost 676 points in the previous four sessions.Similarly, the wide-based National Stock Exchange index Nifty, fell by 23.55 points, or 0.40 per cent, to 5,892.75.Brokers said profit-booking by funds and retail investors at existing higher levels amid a mixed trend in the Asian region mainly influenced the sentiment.