Sesquiterpenes from the fruits of Piper longum L. and their anti-inflammatory activity

The fruits of Piper longum are called long pepper, which are well-known culinary spice as well as traditional medicine. In present work, thirteen sesquiterpenes including four undescribed compounds were isolated from P. longum fruits. Compound 1 was a rare methylated bisabolane-type sesquiterpene. Compounds (−)-3 and (+)-3 were a pair of enantiomers of an uncommon humulane which were separated by chiral HPLC. The absolute configurations of compounds 1–3 were confirmed through the means of spectroscopic data analyses, ¹³C NMR calculations employing DP4+ probability analyses, and ECD calculations. Compounds 2 and 11 presented moderated inhibitory effect on the NO release in LPS-induced RAW264.7 cells with IC₅₀ values of 30.65 ± 0.90 and 38.48 ± 2.42 μM, respectively. Above results enriched the chemical information of P. longum fruits, and meanwhile provided scientific evidences for the anti-inflammatory function of P. longum fruits.