Nitric oxide inhibition and procollagen type I peptide synthesis activities of a phenolic amide identified from the stem of Lycium chinense miller

The bioactivities of boxthron fruits, a source of oriental medicine, are well known, whereas phytochemical studies of the boxthorn stem are rare. In this study, the stem extract of boxthorn (Lycium chinense Miller) and its subfractions were evaluated for their effects on nitric oxide (NO) inhibition and procollagen type I peptide (PIP) synthesis. A phenolic amide isolated from the stem extract was also assayed for these effects. The compound, N-transferuloyltyramine, was identified by¹H,¹³C, and 2D-nuclear magnetic resonance analyses. In NO inhibition, the chloroform fraction (CF) exhibited the strongest inhibitory activity (MIC₅₀ = 24.69 μg/ml) among the subfractions of the ethanol extract (EE). N-transferuloyltyramine isolated from the CF showed strong NO inhibitory activity, presenting with an MIC₅₀ of 31.36 μg/ml. The EE, CF, and N-trans-feruloyltyramine shown to have NO inhibition activity were assayed for the activity of PIP synthesis. The EE and CF showed relatively high PIP values of 38.8% and 24.21% at 100 μg/ml, respectively. The PIP value for 20 μg/ml N-trans-feruloyltyramine showed a 36% increase compared with the non-treated control, whereas that treated with 20 μg/ml ascorbic acid as a positive control showed a 13% increase. The results suggest that the proper stem extract of boxthorn stem could be efficiently used to produce good cosmetic effects.