Compounds with anti-neuroinflammatory activity from aerides falcata

In this study, a plant from the Orchidaceae family, Aerides falcata, was investigated for its chemical constituents and anti-neuroinflammatory activity. A total of ten compounds were isolated and characterized. The isolated compounds included a new compound which was named aerifalcatin and nine known compounds: n-eicosyl-trans-ferulate, denthyrsinin, 2,4-dimethoxy-3,7-dihydroxyphenanthrene, 2,7-dihydroxy-3,4,6-trimethoxyphenanthrene, 3,7-dihydroxy-2,4,6-trimethoxyphenanthrene, agrostonin, syringaresinol, trans-n-feruloyltyramine, and trans-n-coumaroyltyramine. All the isolated compounds were evaluated for their anti-neuroinflammatory activity, except for trans-n-coumaroyltyramine, which was excluded due to its insufficient amount. In vitro testing was conducted on LPS-induced BV2 microglia cells to evaluate their potential anti-neuroinflammatory activity using NO inhibition model. Minocycline, a neuroinflammatory modulator, was used as a positive control. Four compounds demonstrated significant deference to inhibit NO production compared to positive control minocycline (IC50 value of 3.41 ± 0.30 µM): aerifalcatin (IC50 value of 0.87 ± 0.45 µM), 2,7-dihydroxy-3,4,6-trimethoxyphenanthrene (IC50 value of 2.47 ± 0.73 µM), agrostonin (IC50 value of 2.55 ± 0.32 µM), and syringaresinol (IC50 value of 1.40 ± 0.17 µM). An ELISA experiment was performed to determine the levels of cytokines (TNF-α and IL-6) for the most potent compounds. The results demonstrated a significant reduction in their expression in activated microglia in a dose-dependent manner, indicating their potential as anti-neuroinflammatory agents.