Five diterpenoids (agallochins A-E) from the mangrove plant Excoecaria agallocha Linn

Chemical examination of the hexane extract of the roots of Excoecaria agallocha Linn collected from the Godavari estuary resulted in the isolation of altogether eleven diterpenoids of which five (1-5) are new. The structures of the new diterpenoids have been elucidated by a study of their physical and spectral (UV, IR, 1H, 13C, DEPT, 1H-1H COSY, NOESY, HMQC, HMBC and MASS) data as 3-oxo-ent-13epi-8(13)-epoxy-15-chloro-14-hydroxylabdane (1), ent-15-chloro-13,14-dihydroxylabd-8(9)-en-3-one (2), ent-15-chloro-labd-8(9)ene-3alpha,13,14-triol (3), ent-11beta-hydroxy-8(14),15-isopimaradien-3-one (4), 8,13-epoxy-3-nor-2,3-seco-14-epilabden-2,4-olide (5). The six known diterpenoids have been characterised respectively as ent-3-oxo-13-epi-manoyl oxide (6), ent-3beta-hydroxy-13-epi-manoyl oxide (7), (13R,14S)-ent-8alpha,13;14,15-diepoxy-13-epi-labdan-3-one (8), ent-16-hydroxy-3-oxo-13-epimanoyl oxide (9), ent-15-hydroxylabda-8(17),13E-dien-3-one (10), labda-8(17),13E-diene-3beta,15-diol (11) by a comparative study of their spectral data with the literature values.