Anti-inflammatory in vitro activities of eleven selected caffeic acid derivatives based on a combination of pro-/anti-inflammatory cytokine secretions and principal component analysis - A comprehensive evaluation.

Eleven compounds including caffeic acid (CA), 4 kinds of caffeoylquinic acid (CQA) and 6 kinds of dicaffeoylquinic acid (DCQA), were selected to evaluate the anti-inflammatory effectiveness using mouse primary peritoneal macrophages in the absence or presence of lipopolysaccharide (LPS). The optimal non-cytotoxic doses of each individual compound were determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Pro-inflammatory (TNF-α, IL-1β, IL-6) and anti-inflammatory (IL-10) cytokines secreted by treated macrophages were analyzed using the enzyme-linked immunosorbent assay. Cytokine secretion profiles of each individual test sample at optimal non-cytotoxic doses were further analyzed using Principal Component Analysis (PCA). The results showed that CA and all selected CQAs exhibited lower cytotoxicity (IC: >50 μmol/l). Both CA and 5-CQA were found to have the most significant contributions for inhibiting pro-inflammatory cytokines, but increasing anti-inflammatory cytokine secretions, evidencing that CA at 10 μmol/l and 5-CQA at 25 μmol/l can be qualified as potent anti-inflammatory agents for treating inflammation-related diseases.