A new geranylated coumarin, (E)-4-(1-hydroxypropyl)-5,7-dihydroxy-6-(3,7-dimethyl-2,6-octadienyl)-8-(3-methyl-1-oxobutyl)coumarin (named surangin D), was isolated from the bark of Mammea siamensis collected in Vietnam, along with four known coumarins, surangins B and C, and theraphins B and C, and