Comparative study of the antioxidant and reactive oxygen species scavenging properties in the extracts of the fruits of Terminalia chebula, Terminalia belerica and Emblica officinalis

Abstract

Background: Cellular damage caused by reactive oxygen species (ROS) has been implicated in several diseases, and hence natural antioxidants have significant importance in human health. The present study was carried out to evaluate the in vitro antioxidant and reactive oxygen species scavenging activities of Terminalia chebula, Terminalia belerica and Emblica officinalis fruit extracts.

Methods: The 70% methanol extracts were studied for in vitro total antioxidant activity along with phenolic and flavonoid contents and reducing power. Scavenging ability of the extracts for radicals like DPPH, hydroxyl, superoxide, nitric oxide, hydrogen peroxide, peroxynitrite, singlet oxygen, hypochlorous acid were also performed to determine the potential of the extracts.

Results: The ability of the extracts of the fruits in exhibiting their antioxative properties follow the order T. chebula >E. officinalis >T. belerica. The same order is followed in their flavonoid content, whereas in case of phenolic content it becomes E. officinalis >T. belerica >T. chebula. In the studies of free radicals' scavenging, where the activities of the plant extracts were inversely proportional to their IC50 values, T. chebula and E. officinalis were found to be taking leading role with the orders of T. chebula >E. officinalis >T. belerica for superoxide and nitric oxide, and E. officinalis >T. belerica >T. chebula for DPPH and peroxynitrite radicals. Miscellaneous results were observed in the scavenging of other radicals by the plant extracts, viz., T. chebula >T. belerica >E. officinalis for hydroxyl, T. belerica >T. chebula >E. officinalis for singlet oxygen and T. belerica >E. officinalis >T. chebula for hypochlorous acid. In a whole, the studied fruit extracts showed quite good efficacy in their antioxidant and radical scavenging abilities, compared to the standards.

Conclusions: The evidences as can be concluded from the study of the 70% methanol extract of the fruits of Terminalia chebula, Terminalia belerica and Emblica officinalis, imposes the fact that they might be useful as potent sources of natural antioxidant.

Figure 1

Total antioxidant activity. Total antioxidant activity of plant extract and trolox. Effect of (a) T. chebula, T. belerica and E. officinalis extracts and (b) reference compound trolox on ABTS radical cation decolorization assay. The percentage of inhibition was plotted against concentration of sample. All data are expressed as mean ± S.D. (n = 6).

Figure 2

DPPH scavenging activity. Effect of the T. chebula, T. belerica and E. officinalis extracts and standard ascorbic acid on DPPH radical scavenging study. The data is expressed as % scavenging of DPPH radicals. The results are mean ± S.D. of six parallel measurements. ***p < 0.001 vs 0 μg/ml.

Figure 3

Hydroxyl radical scavenging assay. Hydroxyl radical scavenging activity of the T. chebula, T. belerica and E. officinalis extracts and the reference compound mannitol. The data represent the percentage of inhibition of deoxyribose degradation. The results are mean ± S.D. of six parallel measurements. ***p < 0.001 vs 0 μg/ml.

Figure 4

Superoxide radical scavenging assay. Scavenging effect of T. chebula, T. belerica and E. officinalis plant extracts and standard quercetin on superoxide radical. The data represents the percentage of superoxide radical inhibition. All data are expressed as mean ± S.D. (n = 6). ***p < 0.001 vs 0 μg/ml.

Figure 5

Nitric oxide radical scavenging assay. The nitric oxide radical scavenging activity of T. chebula, T. belerica and E. officinalis extracts and standard curcumin. The data represents the % of nitric oxide inhibition. Each value represents mean ± S.D. (n = 6). ***p < 0.001 vs 0 μg/ml.

Figure 6

Peroxynitrite anion scavenging assay. The peroxynitrite anion scavenging activity of T. chebula, T. belerica and E. officinalis plant extracts and standard gallic acid. Each value represents mean ± S.D. (n = 6). *p < 0.05, **p < 0.01 and ***p < 0.001 vs 0 μg/ml.

Figure 7

Singlet oxygen scavenging assay. Effect of T. chebula, T. belerica and E. officinalis plant extracts and standard lipoic acid on the scavenging of singlet oxygen. The results are mean ± S.D. of six parallel measurements. **p < 0.01 and ***p < 0.001 vs 0 μg/ml.

Figure 8

HOCl scavenging assay. Hypochlorous acid scavenging activity of T. chebula, T. belerica and E. officinalis plant extracts and standard ascorbic acid. All data are expressed as mean ± S.D. (n = 6). **p < 0.01 and ***p < 0.001 vs 0 μg/ml.

Figure 9

Reducing power assay. The reductive ability of T. chebula, T. belerica and E. officinalis extracts and standard Ascorbic acid. The absorbance (A₇₀₀) was plotted against concentration of sample. Each value represents mean ± S.D. (n = 6). *** p < 0.001 vs 0 mg/ml.

Figure 10

Correlation of antioxidant activity with phenolic and flavonoid contents. The relationship between (a) total phenolic content or (b) total flavonoid content in individual fruit and their antioxidant capacity. The correlation analyses were described as linear correlation coefficient (R). The differences were considered statistically significant if p < 0.05.