New natural furfural derivatives from the leaves and stems of Pogostemon cablin

A new furfural derivative, pogoscafuran A (1), a new natural product, HMF levulinate (2), together with four known compounds (3-6) were isolated from an extract of the leaves and stems of Pogostemon cablin (Blanco) Benth. Their structures were elucidated on the basis of extensive spectroscopic analyses and single-crystal X-ray crystallography. Compound 1 was the first example of natural furfural derivative with a unique C5-C1' linkage between a molecule of furfural and 3-methyl-2-cyclopentenone moiety. The plausible biogenetic pathway for the new compound 1 was proposed. All these isolated compounds were tested for their inhibitory effects on the nitric oxide (NO) production induced by lipopolysaccharide in RAW264.7 cells, and only compound 1 exhibited weak inhibitory activity.