BENGALURU, Aug 25 (Reuters) - Indian shares reversed course to close lower on Thursday, dragged down by tech and the expiry of monthly derivative contracts, while investors waited for clues on future rate hikes in the U.S. from a key central bank event.

The NSE Nifty 50 index was 0.47% lower at 17,522.45, after rising as much as 0.7% in the session.

The S&P BSE Sensex fell 0.53% to 59,774.72.

"Amid heightened volatility, investors pruned their long positions on the F&O expiry day due to the uncertain global economic scenario," said Shrikant Chouhan, head of equity research for retail at Kotak Securities, adding that concerns over Fed's speech weighed.

Global shares rose as investors stay focused on comments from Federal Reserve Chair Jerome Powell on Friday.

In India, Adani Ports and Special Economic Zone was the top loser on the Nifty 50 after it fell 2.4%.

The Nifty IT index was down 0.87% with IT major Infosys Ltd the top loser, shedding 1.3%.

Consumer stocks also fell, as heavyweights ITC Hindustan Unilever dropped 0.5% each.

Mid-cap stocks have been an active participant in the Indian market recently, with the Nifty Mid-cap 100 index rising 4.4% this month. The index closed 0.06% lower on Thursday.

Bucking the trend, the Nifty PSU Bank index was up 2.7% to its highest in over four months.

(Reporting by Tanvi Mehta in Bengaluru; Editing by Dhanya Ann Thoppil)