PROFIT-TAKING took the froth off sentiment yesterday as cautious investors dominated. Hang Seng Index futures in August fell 150 points to 9,535 while in September it fell 160 points to 9,530. The cash market fell 109 points to 9,585. Turnover was a moderate 12,701 contracts. Persistent selling saw both markets slide all day. Index option trading was also moderate, at 2,204 contracts. Jardine Fleming said: ''Spread trades continued to be popular in the options market.'' Overseas investors sold September 9,800-10,600 two-by-one and 9,600-10,600 call spreads, said the brokerage. ''Local bears expecting a larger correction on the market bought August 9,000 puts,'' said JF. Implied volatility in the front month was flat, at around 28 per cent. At-the-money implied volatility in call and puts in September was 30 per cent and 31 per cent respectively. In December they were the same and in March they were 32 per cent and 31 per cent respectively. The Hang Seng Index 100-day historic volatility level was at 34 per cent. Failure to break through 9,770 was seen by some technical analysts as negative for those hoping for more gains in trading in the near term.