Isolation and Identification of Bioactive Fatty Acid Amides From Piper longum Fruits

Four pairs of previously undescribed fatty acid amide enantiomers [(+)-1/(-)-1 - (+)-4/(-)-4] bearing a trans-epoxide, and 12 known compounds (5-14) were isolated from the fruits of Piper longum L. Their structures were elucidated using spectroscopic methods, including HRMS and NMR, and by comparing with literatures. The absolute configuration of the novel compounds was determined through electronic circular dichroism (ECD) calculations. The bioactivity of all isolated compounds was evaluated, revealing that compounds (+)-4 and (+)-7 exhibited significant anti-inflammatory activity, with IC₅₀ values of 10.62 ± 0.80 and 8.93 ± 0.59 μM, respectively (IC₅₀ value of the positive control, andrographolide, was 5.85 ± 0.26 μM). In the cytotoxicity assay, compound 10 demonstrated a potent cytotoxic effect against HT-29 cells with an IC₅₀ value of 6.43 ± 0.36 μM; compounds 6, (+)-7, and 9 displayed moderate cytotoxic activity against HT-29 cells with IC₅₀ values between 10 and 20 μM (IC₅₀ value of the positive control, doxorubicin, was 0.22 ± 0.02 μM). These findings suggested that fatty acid amides from P. longum possess promising anti-inflammatory and cytotoxic properties.