Rapid Communication Rhizophorin B: A novel beyerane diterpenoid from the Indian mangrove plant Rhizophora mucronatat

Rhizophora mucronata Lam (family: Rhizophoraceae) is one of the two mangrove plants of the Rhizophora genus that occur along the tidal shores and creeks of India including the Andaman and Nicobar Islands• Besides being a source of tannins , R. mucronata is known to be powerful astringent and is used in the treat ment of haemmorrhage, haematuria and anginaz. The bark of R. mucronata is also used as a cure for diabetesz. A variety of steroid and triterpenoid derivatives have been reported from the leaves3.4 and bark of thi s plant. In our continuing interest on the chemical constituents of the Indian mangrove plants' we have examined the roots of R. mucronata collected from the Mangalore coast of India and reported recentl y the isolation of a novel seco labdane diterpenoid rhizophorin-A from the eth yl acetate extract . Further, elution of the residue from the EtOAc extract over a column of a silica gel with hexane:EtOAc (7 :3) furnished another interes tin g beyerane diterpenoid , designated rhizophorin-B . Structural elucidation of rhizophorin-B using all spectral data and some chemical reactions is presented here.