Ann Loeb Bronfman, 78, who descended from two family fortunes, married into another and became a philanthropist devoted to wide-ranging causes, died April 5 at Sibley Memorial Hospital in Washington. She had complications from emphysema.

Descended from pillars of Wall Street investment banking, Mrs. Bronfman attended exclusive boarding schools and enjoyed a privileged upbringing of elite supper dances.

She was married for two decades to Edgar M. Bronfman Sr., who became head of his family’s billion-dollar Seagram distillery company. The Bronfmans divorced in 1973.

In a period when some of America’s wealthiest families found their children targets of often-violent kidnappings, the Bronfmans’ eldest son, Samuel, was abducted from a family estate in suburban New York on Aug. 9, 1975.

In a brief phone call placed to his father, the 21-year-old Samuel Bronfman said he had been taken against his will and blindfolded.

He was held for more than a week before his father paid a $2.3 million ransom — arbitrarily reduced from the initial request of $4.6 million. In a predawn raid, the FBI and New York City police rescued Samuel Bronfman from a Brooklyn apartment, where he was found with his hands bound and his eyes and mouth covered with adhesive tape.

The captors — a former limousine operator and former fireman — were acquitted of kidnapping but convicted of extortion charges and spent several years in prison. The ransom money was recovered.

In contrast to her hard-driving and mercurial ex-husband, Mrs. Bronfman led a quiet life of charitable endeavors.

Living in Washington since 1985, she gave to causes including the arts, education and victims of domestic abuse. The D.C. Jewish Community Center named its gallery in her honor.

Among other organizations and institutions, she gave to International Planned Parenthood, the Visiting Nurse Association of New York and the New York Public Library.

Ann Margaret Loeb was born Sept. 19, 1932, in New York City. Her father, John Langeloth Loeb Sr., was a Wall Street investment banker whose company was a predecessor of Shearson Lehman/American Express.

Her mother, the former Frances Lehman, was a scion of the Lehman Brothers banking firm. Her parents were major benefactors of Harvard University and other colleges.

In 1950, Ann Loeb graduated from the private Rosemary Hall girls’ school in Connecticut. She attended Bennington College in Vermont before marrying Bronfman in 1953.

The union fostered many business ventures, with the Bronfmans using the Loeb, Rhoades & Co. investment firm to buy swaths of land and diversify its holdings into the entertainment and petroleum industries.

In addition to her home in the District, where she displayed many family art treasures and heirlooms, Mrs. Bronfman enjoyed remodeling her Victorian house on Mackinac Island, Mich.

Survivors include five children, Samuel Bronfman of Atherton, Calif., Edgar Bronfman Jr. of Manhattan, who is chairman of the Warner Music Group, Holly Bronfman Lev of Charlottesville, Matthew Bronfman of Westchester County, N.Y., and Adam Bronfman of Park City, Utah; a sister; two brothers, including her twin; 25 grandchildren; and two great-grandchildren.