A novel biphenyl ether, 4,4'-diallyl-2,3'-dihydroxybiphenyl ether, 3,5'-diallyl-2'-hydroxy-4-methoxy-biphenyl and 5,5'-diallyl-2,2'-dihydroxybiphenyl (magnolol) were isolated from the leaves of Magnolia virginiana and characterized by spectral and chemical means. All three compounds and their methoxy analogues were very toxic to brine shrimp and mosquito larvae and showed strong anti-fungal and anti-bacterial activities.