Angular dihydropyranocoumarins from the flowers of Peucedanum japonicum and their aldo-keto reductase inhibitory activities

Twenty-one angular dihydropyranocoumarins and a linear furanocoumarin, including four previously undescribed compounds (1–4), were isolated from the flowers of Peucedanum japonicum (Umbelliferae). The structures of 1–4, along with their absolute stereochemistry, were determined to be (3′S,4′S)-3′-O-propanoyl-4′-O-(3‴-methyl-2‴-butenoyl)khellactone (1), (3′S,4′S)-3′-O-propanoyl-4′-O-(2‴-methyl-2‴Z-butenoyl)khellactone (2), (3′S,4′S)-3′-O-propanoyl-4′-O-(2‴-methylbutanoyl)khellactone (3), and (3′S,4′S)-3′-O-(2″-methylpropanoyl)-4′-O-(3‴-methyl-2‴-butenoyl)khellactone (4) using one- and two-dimensional nuclear magnetic resonance, high-resolution electrospray ionization mass spectroscopy, and electronic circular dichroism spectroscopy. In addition, the absolute configuration of the three angular dihydropyranocoumarins (5–7) was determined for the first time in this study. Among the previously reported compounds isolated in this study, 8 and 9 were isolated for the first time from the genus Peucedanum, whereas 10 and 11 were previously unreported and had not been isolated from P. japonicum to date. Furthermore, all isolated compounds were evaluated for their aldo–keto reductase 1C1 inhibitory activities on A549 human non-small-cell lung cancer cells. Compounds 10 and 12 exhibited substantial AKR1C1 inhibitory activities with IC50 values of 35.8 ± 0.9 and 44.2 ± 1.5 μM, respectively. Four previously undescribed angular dihydropyranocoumarins (1–4), along with eighteen known compounds were identified from the flowers of Peucedanum japonicum. Bioactivity assay revealed that two isolates (10 and 12) showed aldo-keto reductase1C1 inhibitory activity. [Display omitted] •Four previously undescribed angular dihydropyranocoumarins were isolated from Peucedanum japonicum.•The absolute configurations of three angular dihydropyranocoumarins were determined.•Four known angular dihydropyranocoumarins were isolated from P. japonicum for the first time.•Compounds 10 and 12 inhibited aldo-keto reductase 1C1 activity for anti-cancer effects.