General unknown screening, antioxidant and anti-inflammatory potential of Dendrobium macrostachyum Lindl

D. macrostachyum is an epiphytic orchid abundant in Southern India and is reported for pain relief in folklore.

The objective of the present study was to determine in vitro free radical scavenging and anti-inflammatory activity of D. macrostachyum and to perform LCMS based metabolic profiling of the plant.

Sequential stem and leaf extracts were assessed for its antioxidant and anti-inflammatory activity by in vitro methods.

The antioxidant activity determined by assays based on the decolourization of the radical monocation of DPPH, ABTS and reducing power. Total amount of phenolics for quantitative analysis of antioxidative components was estimated. In vitro anti-inflammatory activity was evaluated using protein denaturation assay, membrane stabilization assay and proteinase inhibitory activity. Methanolic extract of plant was subjected to LCMS.

The stem ethanolic extracts exhibited significant IC50 value of 10.21, 31.54 and 142.97 μg/ml respectively for DPPH, ABTS radical scavenging and reducing power activity. The ethanol and water extract was highly effective as albumin denaturation inhibitors (IC50 = 114.13 and 135.818 μg/ml respectively) and proteinase inhibitors (IC50 = 72.49 and 129.681 μg/ml respectively). Membrane stabilization was also noticeably inhibited by the stem ethanolic extract among other extracts (IC50 = 89.33 μg/ml) but comparatively lower to aspirin standard (IC50 = 83.926 μg/ml). The highest total phenol content was exhibited by ethanolic stem and leaf extracts respectively at 20 and 16 mg of gallic acid equivalents of dry extract. On LCMS analysis 20 constituents were identified and it included chemotaxonomic marker for Dendrobium species.

The results showed a relatively high concentration of phenolics, high scavenger activity and high anti-inflammatory activity of the stem extract compared to the leaf extract. The results indicate that the plant can be a potential source of bioactive compounds.