Anti-biofilm, nitric oxide inhibition and wound healing potential of purpurin-18 phytyl ester isolated from Clinacanthus nutans leaves.

Aims: Clinacanthus nutans (C. nutans) has demonstrated anti-inflammatory activity, however, the active compound generating this activity remains unknown. The aim of this study was to identify the bioactive compound in C. nutans responsible for its anti-inflammatory, in-vitro wound healing, and anti-biofilm activities.

Main Methods: A pure compound was isolated from the chloroform extract (CE) of C. nutans leaves by chromatographic techniques and bioassay-guided fractionation. This compound's structure was determined by spectroscopic analyses (FTIR/NMR/HRES-MS). Biological activities were evaluated using cytotoxicity, nitric oxide (NO), wound scratch, anti-microbial activity, and anti-biofilm assays; and the compound's bactericidal depth into the biofilm was visualized by confocal laser scanning microscopy.

Key Findings: CE and its pure isolated compound, purpurin-18 phytyl ester (P18PE), significantly inhibited lipopolysaccharide (LPS)-induced NO production in RAW 264.7 cells at concentrations of 100 μg/ml and 10-100 μg/ml, respectively. These concentrations significantly induced wound closure by human gingival fibroblasts. CE (100-1000μg/ml) and P18PE (1-500 μg/ml) did not inhibit Streptococcus (S.) mutans growth. However, these concentrations significantly reduced S. mutans biofilm formation below 50% at 250 μg/ml for CE, and 25 μg/ml for P18PE (p<0.05).

Significance: C. nutans contains a bioactive compound, P18PE, which exhibits anti-inflammatory, in-vitro wound healing, and anti-biofilm activities.