Four persons were indicted yesterday for stealing confidential information about planned corporate mergers and acquisitions from two major New York investment banking firms, Morgan Stanley & Co. and Kuhn Loeb & Co.

A fifth member of the alleged conspiracy pleaded guilty on Nov. 13 to related charges, according to the U.S. Attorney's Office in Manhattan where the 27-count criminal indictment was returned.

The indictment, charging violations of the federal mail fraud and conspiracy laws, alleges that the five persons bought stock in companies that were targets for takeover by other companies. The two investment banking houses handled the financing of the mergers and acquisitions.

According to the indictment, the five acquired stock in some 17 companies when they were secret takeover targets and before the investing public was aware of the fact. Typically, the stock in a company being taken over rises sharply when the news gets out.

The five reportedly made about $600,000 in profits between 1974 and early 1978 when the alleged offenses took place.

The indictment names E. Jacques Courtois Jr., James Mitchell Newman (also known as Barnett), Franklin Carniol and Constantine Spyropoulos (a/k/a Patrick). The fifth alleged conspirator, Adrian Antoniu, pleaded guilty to a prosecutor's charge that he schemed to profit on confidential information.

Newman, 37, now lives in New York City; Carniol, 35, in Brussels; and Spryopoulos, 34, in Athens.

Courtois and Antoniu, who were recruited by Morgan Stanley in 1972 after graduating from Harvard Business School, were specifically charged with violating their fiduciary duty to the two firms.

Courtois rose to vice president in the mergers and acquisitions department before leaving the firm in 1979. Courtois, who is 33, now lives in Bogota, Columbia, according to the indictment.

Antoniu was an associate at Morgan Stanley until 1975 when he joined the mergers and acquisitions department of Kuhn Loeb (now Lehman Brothers Kuhn Loeb). The indictment says that Antoniu left that firm in 1978 and that he now lives in Italy.

"Our feeling is we've been violated and we're damned upset about it," said a high official at Morgan Stanley who asked that his name not be used. "But there's nothing we could have done to stop it. They stole confidential information against our own policies and procedures, if the allegations are correct."

According to the indictment, Courtois and Antoniu covertly disclosed to the three other defendents confidential information regarding impending mergers and acquisition being structured and negotiated by their two firms.

Substantial amounts of stock in the targeted companies was purchashed through secret bank accounts in Bermuda, the Bahamas, Luxembourg and Switzerland.