Sesquiterpenes from Neurolaena lobata and Their Antiproliferative and Anti-inflammatory Activities

Five new sesquiterpenes, neurolobatin A (1), neurolobatin B (2), 5β-hydroxy-8β-isovaleroyloxy-9α-hydroxycalyculatolide (3), 3-epi-desacetylisovaleroylheliangine (4), and 3β-acetoxy-8β-isovaleroyloxyreynosin (5), were isolated from the aerial parts of Neurolaena lobata. The structures were established by means of a combined spectroscopic data analysis, including ESIMS, APCI-MS, and 1D- and 2D-NMR techniques. Neurolobatin A (1) and B (2) are unusual isomeric seco-germacranolide sesquiterpenes with a bicyclic acetal moiety, compounds 3 and 4 are unsaturated epoxy-germacranolide esters, and compound 5 is the first eudesmanolide isolated from the genus Neurolaena. The isolated compounds (1–5) were shown to have noteworthy antiproliferative activities against human tumor cell lines (A2780, A431, HeLa, and MCF7). The anti-inflammatory effects of 1–5, evaluated in vitro using LPS- and TNF-α-induced IL-8 expression inhibitory assays, revealed that all these compounds strongly down-regulated the LPS-induced production of IL-8 protein, with neurolobatin B (2) and 3-epi-desacetylisovaleroylheliangine (4) being the most effective.