The 30-share index, which commenced the day higher by 78 points, fell back by 28.32 points to trade at 18,209.99 points at 1300 hrs as metal, oil and gas and banking stocks declined.
The broad-based National Stock Exchange index Nifty eased by 6.60 points to 5,479.55 points, after rising to 5,510.40 in early trade.
Selling pressure sparked on reports that food inflation rose marginally to 10.86 per cent for the week ended 21st August, after the previous two-week decline.