Isolation and identification of chromone and pyrone constituents from Aloe and their anti-inflammatory activities

Aloe has long been used in food products, beverages and cosmetics, and as a traditional medicine to treat various diseases in many countries. In the present study, a new chromone, aloe resin E (1), and a new pyrone, aloenin C (11), together with thirteen known compounds were isolated from aqueous dissolved Aloe exudates and their structures were identified by spectroscopic analysis. Nuclear factor kappa B (NF-κB) inhibitory activity of the isolated compounds was evaluated using an NF-κB luciferase assay in HepG2 cells. Among them, 7-hydroxy-5-(hydroxymethyl)-2-methylchromone (4), 5-((S)-2′-oxo-4′-hydroxypentyl)-2-hydroxymethylchromone (9), and aloenin aglycone (13) showed significant inhibitory effects against TNFα-induced NF-κB transcriptional activity in a dose-dependent manner with IC50 values ranging from 14.92 to 18.70 µM. Furthermore, the transcriptional inhibition of compounds 4, 9, and 13 was confirmed by a decrease in the expression of inducible nitric oxide synthase (iNOS) and intercellular adhesion molecule-1 (ICAM-1) genes in HepG2 cells.