Chemical constituents of the flowers of Azadirachta indica

Studies on the chemical constituents of the flowers of Azadirachta indica have led to the isolation of two new flavanones, flowerine (=5-hydroxy-7,4'-dimethoxy-8-(3-methylbut-2-enyl)flavan-4-one; 1) and flowerone (=5,7,8,4'-tetrahydroxy-3'-(3-methylbut-3-enyl)flavan-4-one; 2), and two new triterpenoids, O-methylazadironolide (=7alpha-(acetoxy)-23xi-methoxy-21,23-epoxy-24,25,26,27-tetranorapotirucalia-1,14,20(22)-trien-3,21-dione; 3) and diepoxyazadirol (=(20S,23S,24R)-7-alpha-(acetoxy)-25-hydroxy-21,24:23,24-diepoxyapotirucalla-1,14-dien-3-one; 4) along with the known triterpenoid trichilenone acetate (=7alpha-(acetoxy)-14,5:21,23-diepoxy-24,25,26,27-tetranorapotirucalla-1,20,22-trien-3-one; 5), two known flavanones, nimbaflavone (=5,7-dihydroxy-4'-methoxy-8,3'-bis(3-methylbut-2-enyl)-flavan-4-one; 6) and 3'-prenylnaringenin (=5,7,4'-trihydroxy-3'-(3-methylbut-2-enyl) flavan-4-one; 7), and 4-(2-hydroxyethyl)phenol (8). Their structures have been elucidated through spectral studies, including 2D-NMR experiments, and chemical transformation. Compounds 5, 7 and 8 are heretofore unreported from any part of tree, while 6 has been isolated earlier from leaves.