A new phenylpropane-pimarane heterodimer and a new ent-kaurene diterpene from the husks of Oryza sativa

Abstract A new phenylpropane-pimarane heterodimer, 2-[( E )-3-(4-hydroxy-3-methoxyphenyl) allylidene] momilactone A ( 1 ), and a new ent -kaurene diterpene, ent -3α,16α-dihydroxy-kauran-19-oic acid ( 2 ), were isolated from the rice husks of Oryza sative L., along with a known ent -kaurene diterpenoid ent -7-oxo-kaur-15-en-19-oic acid ( 3 ). Their structures were determined by spectroscopic means, including nuclear magnetic resonance (NMR) and mass spectrometry (MS) techniques. Compound 3 was isolated as a natural product for the first time. These compounds were tested for their in vitro antifungal activity against rice pathogenic fungi Magnaporthe grisea and Rhizoctonia solani . Compounds 1 and 3 were found to show anti-fungal activity against M. grisea and R. solani with MIC values ranging from 6.25 to 25 μg/mL. No inhibitory activity was detected for compound 2 in this bioassay.