Abstract
BackgroundThe medicinal orchid Dendrobium moniliforme contains water-soluble polysaccharides, phenanthrenes, bibenzyl derivatives, and polyphenol compounds. This study explored the antioxidant and cytotoxic activities of D. moniliforme extracts and detected their bioactive compounds.MethodsPlant material was collected from the Daman of Makawanpur district in central Nepal. Plant extracts were prepared from stems using hexane, chloroform, acetone, ethanol and methanol. The total polyphenol content (TPC) in each extract was determined using Folin-Ciocalteu’s reagent and the total flavonoid content (TFC) in each extract was determined using the aluminium chloride method. The in vitro antioxidant and cytotoxic activities of each extract were determined using DPPH (2,2-diphenyl-1-picrylhydrazyl) and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assays respectively. Gas chromatography and mass spectrometry (GC-MS) analysis was used to detect bioactive compounds.ResultsTPC content was highest (116.65 μg GAE/mg of extract) in D. moniliforme chloroform extract (DMC) and TFC content was highest (116.67 μg QE/mg of extract) in D. moniliforme acetone extract (DMA). D. moniliforme hexane extract (DMH) extract showed the highest percentage of DPPH radical scavenging activity (94.48%), followed closely by D. moniliforme ethanol extract (DME) (94.45%), DMA (93.71%) and DMC (94.35%) at 800 μg/ml concentration. The antioxidant capacities of DMC, DMA, DMH and DME, which were measured in IC50 values, were much lower 42.39 μg/ml, 49.56 μg/ml, 52.68 μg/ml, and 58.77 μg/ml respectively than the IC50 of D. moniliforme methanol extract (DMM) (223.15 μg/ml). DMM at the concentration of 800 μg/ml most inhibited the growth of HeLa cells (78.68%) and DME at the same concentration most inhibited the growth of U251 cells (51.95%). The cytotoxic capacity (IC50) of DMM against HeLa cells was 155.80 μg/ml of extract and that of DME against the U251 cells was 772.50 μg/ml of extract. A number of bioactive compounds were detected in both DME and DMM.ConclusionThe fact that plant extract of D. moniliforme has a number of bioactive compounds which showed antioxidant and cytotoxic activities suggests the potential pharmacological importance of this plant.
Highlights
The medicinal orchid Dendrobium moniliforme contains water-soluble polysaccharides, phenanthrenes, bibenzyl derivatives, and polyphenol compounds
Plant extracts have significant amounts of total polyphenol and flavonoid contents Total polyphenol contents (TPCs) in the extracts were calculated using the linear equation for standard gallic acid (y = 0.0154 x – 0.3285; R2 = 0.989; p = 0.005) and total flavonoid contents (TFCs) was calculated using the linear equation for standard quercetin hydrate (y = 0.0242 x – 0.1845; R2 = 0.976; p = 0.012)
The TFC of D. moniliforme acetone extract (DMA) (116.67 μg quercetin equivalent (QE)/mg of extract) was much higher than it was in other extracts, though the TFC of D. moniliforme ethanol extract (DME) was high (Fig. 1)
Summary
The medicinal orchid Dendrobium moniliforme contains water-soluble polysaccharides, phenanthrenes, bibenzyl derivatives, and polyphenol compounds. One species of Dendrobium, Dendrobium moniliforme (synonym D. candidum), is a valuable medicinal orchid found across southeast and south Asia [1, 6, 7] It contains water-soluble polysaccharides [8, 9], phenanthrenes, bibenzyl derivatives, and polyphenolic compounds [10,11,12,13,14,15]. Bibenzyl derivatives isolated from D. moniliforme were examined for their antioxidant capacity using DPPH free-radical scavenging assay [11, 13, 14], a popular tool because of its simplicity and high sensitivity. A compound’s antioxidant effect is proportional to the disappearance of DPPH radicals in test samples [19]
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