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RESEARCH PRODUCT

Two new diterpenoids from kencur (Kaempferia galanga): Structure elucidation and chemosystematic significance

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Abstract Aromatic ginger or kencur (Kaempferia galanga L.) rhizomes are ground as a spice or pickled for consumption in south-east Asian cuisines; although widely used, until recently it has been less studied chemically than white and red ginger. Hydro-distillate extracts have identified several compounds that exhibit anticancer activity against select tumor cell lines in vitro, and most recently chemical analyses have focused on rhizome metabolites present in organic extracts. Here we report on two new diterpenoids including Δ8(14),15 polyhydroxlated isopimardienes, 1α-hydroperoxy-2α,6,7-trihydroxy-isopimara-6(7),8(14),15-triene (kaemgalangol E; 1) and 1α,7β-hydroxy-isopimara-8(14),15-diene (kaemgalangol F; 2), along with the known compound, marginaol A (3) from a CH2Cl2/MeOH extract of the rhizome. Structural elucidation was based on spectroscopic analysis including HRMS, FTIR, as well as 1D and 2D NMR. A proposed biosynthetic pathway for compounds 1–3 is presented and chemo-systematic analysis indicates that K. galanga has the enzymatic machinery to synthesize an array of Δ8(14),15 isopimardienes as well as methoxylated cinnamates.