Isolation, X-ray crystal structure and DFT calculations for 9β,13β-epoxy-7-abietene from the essential oil of Tetradenia riparia

•Column chromatography fractionation of the essential oil of Tetradenia riparia.•Isolation of the abietane diterpenoid 9β,13β-epoxy-7-abietene as reddish crystals.•First report on the crystalline structure of 9β,13β-epoxy-7-abietene.•DFT calculations support the proposed stereochemistry for 9β,13β-epoxy-7-abietene. In the pursuit of new botanical natural products with potential for the development of natural nematicides, the essential oil of Tetradenia riparia was chemically characterized by GC–MS and subjected to nematicidal activity tests. Two compounds identified as major components by GC–MS analysis could not be determined by comparing their mass spectra with library data. Fractionation of the oil by column chromatography allowed isolation of the compounds, identified as 9β,13β-epoxy-7-abietene and 6,7-dehydroroyleanone. Both compounds were obtained as suitable crystals for single-crystal X-ray diffraction analysis. This work facilitated the pioneering report of the crystal structure of the diterpenoid abietane 9β,13β-epoxy-7-abietene, previously reported as an amorphous solid. DFT calculations performed at the B3LYP-D3/Def2-SVP level provided insight into the relative stability and proposed stereochemistry of 9β,13β-epoxy-7-abietene. Finally, the essential oil did not exhibit significant activity in inhibiting egg hatching or causing mortality of the phytopathogenic nematode Meloidogyne incognita. [Display omitted]