Phytochemical analysis and free radical scavenging activity of medicinal plants Gnidia glauca and Dioscorea bulbifera.

Gnidia glauca and Dioscorea bulbifera are traditional medicinal plants that can be considered as sources of natural antioxidants. Herein we report the phytochemical analysis and free radical scavenging activity of their sequential extracts. Phenolic and flavonoid content were determined. Scavenging activity was checked against pulse radiolysis generated ABTS(•+) and OH radical, in addition to DPPH, superoxide and hydroxyl radicals by biochemical methods followed by principal component analysis. G. glauca leaf extracts were rich in phenolic and flavonoid content. Ethyl acetate extract of D. bulbifera bulbs and methanol extract of G. glauca stem exhibited excellent scavenging of pulse radiolysis generated ABTS(•+) radical with a second order rate constant of 2.33 × 10(6) and 1.72 × 10(6), respectively. Similarly, methanol extract of G. glauca flower and ethyl acetate extract of D. bulbifera bulb with second order rate constants of 4.48 × 10(6) and 4.46 × 10(6) were found to be potent scavengers of pulse radiolysis generated OH radical. G. glauca leaf and stem showed excellent reducing activity and free radical scavenging activity. HPTLC fingerprinting, carried out in mobile phase, chloroform: toluene: ethanol (4: 4: 1, v/v) showed presence of florescent compound at 366 nm as well as UV active compound at 254 nm. GC-TOF-MS analysis revealed the predominance of diphenyl sulfone as major compound in G. glauca. Significant levels of n-hexadecanoic acid and octadecanoic acid were also present. Diosgenin (C₂₇H₄₂O₃) and diosgenin (3á,25R) acetate were present as major phytoconstituents in the extracts of D. bulbifera. G. glauca and D. bulbifera contain significant amounts of phytochemicals with antioxidative properties that can be exploited as a potential source for herbal remedy for oxidative stress induced diseases. These results rationalize further investigation in the potential discovery of new natural bioactive principles from these two important medicinal plants

Superoxide anion scavenging activity of plant extracts.

<p>AA = Ascorbic acid; the data is indicated as the mean ± SEM; [<i>n = </i>3]. Data with asterisk (*) shows significant difference (<i>P</i><0.05), two-tailed student t-test.</p

Superoxide radical scavenging activity of plant extracts.

<p>AA = Ascorbic acid; the data is indicated as the mean ± SEM; [<i>n = </i>3]. Data with asterisk (*) shows significant difference (<i>P</i><0.05), two-tailed student t-test.</p

HPTLC fingerprint of extracts of <i>G. glauca</i> flower.

<p>(1) Petroleum ether extract, (2) Ethyl acetate extract, (3) Methanol extract, (4) Ethanol extract (70% v/v) at (A) 254 nm, (B) 366 nm and (C) 600 nm. Standards used are quercetin (Q), myricetin (M) and catechin (C) in lane 5.</p

Pulse radiolysis generated OH radical scavenging by plant extracts.

<p>Pulse radiolysis generated OH radical scavenging by plant extracts.</p

Principal component analysis of antioxidant activity represented by scatter plot.

<p>GGF - <i>G. glauca</i> flower; GGL - <i>G. glauca</i> leaf; GGS – <i>G. glauca</i> stem; DBB – <i>D. bulbifera</i> bulbs; PE: Petroleum ether extract; EA: Ethyl acetate extract; MeOH: Methanol extract; EtOH: Ethanol extract (70%).</p

Total flavonoid content of plant extracts.

<p>The data is indicated as the mean ± SEM; [<i>n = </i>3]. Data with asterisk (*) shows significant difference (<i>P</i><0.05), two-tailed student t-test.</p

Total phenolic content of plant extracts.

<p>The data is indicated as the mean ± SEM; [<i>n = </i>3]. Data with asterisk (*) shows significant difference (<i>P</i><0.05), two-tailed student t-test.</p

Ferric reducing antioxidant power of plant extracts.

<p>Ferric reducing antioxidant power of plant extracts.</p

DPPH radical scavenging activity by plant extracts.

<p>AA = Ascorbic acid; the data is indicated as the mean ± SEM; [<i>n = </i>3]. Data with different asterisks (*) shows significant difference (<i>P</i><0.05), two-tailed student t-test.</p