In vitro Antioxidant Activities and Polyphenol Contents of Seven Commercially Available Fruits

Abstract

Background: Fruits are considered one of the richest sources of natural antioxidants. Their consumption has been linked to the prevention of oxidative stress-induced diseases.

Objective: In this study, in vitro antioxidant activities of blueberry, jackfruit, blackberry, black raspberry, red raspberry, strawberry, and California table grape extracts were evaluated.

Materials and methods: Antioxidant activities were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant potential (FRAP), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), nitric oxide (NO), superoxide anion (O₂^-) scavenging assays, and ferric reducing power.

Results: Black raspberry extract had the highest phenolic (965.6 ± 2.9 mg gallic acid equivalents [GAE]/g), flavonoid (186.4 ± 1.7 mg quercetin equivalents/g), and proanthocyanidin (2677 ± 71.1 mg GAE/g) contents. All fruit extracts exhibited increasing radical scavenging activities with increased concentrations. At 100 μg/ml, red raspberry extract showed the highest ferric reducing power (A₇₀₀ =0.3 ± 0.0052) and FRAP activity (A₅₉₃ =11.43 mM Fe²⁺/g). Black raspberry extract (100 μg/ml) exhibited the highest DPPH activity (A₅₁₇ =89.03 ± 0.0471). Jackfruit extract (100 μg/ml) had the highest ABTS (A₇₃₄ =35.6 ± 0.613), NO (A₅₄₀ =81.7 ± 0.2), and O₂^- radical scavenging (A₂₃₀ =55.5 ± 0.2) activities. Positive correlations were observed between IC₅₀ values for different radical scavenging activities and different polyphenolics. Red raspberry extract had the highest Pearson's coefficient values (0.952-1) between total phenolics, flavonoids, and proanthocyanidins and DPPH and superoxide radical scavenging activities.

Conclusions: The antioxidant rich fruits in this study are good source of functional food and nutraceuticals that have the potential to improve human health.

Summary: All fruit extracts exhibited increasing radical scavenging activities with increased concentrationsBlack raspberry extract is enriched in total phenols, flavonoids, and proanthocyanidins and showed the highest 2,2-diphenyl-1-picrylhydrazyl scavenging activity and red raspberry extract showed the highest ferric reducing power and ferric reducing antioxidant potential activityJackfruit extract exhibited the highest 2,2'azino-bis (3-ethylbenzothiazoline-6-sulfonicacid) diammonium salt, nitric oxide, O₂- scavenging activitiesPositive correlations were observed between IC50 values for different radical scavenging activities and different polyphenolics. Abbreviations Used: Abs: Absorbance, ABTS: 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, BHT: Butylated hydroxytoluene, DPPH: 2,2-diphenyl-1-picrylhydrazyl, DW: Dry weight, FRAP: Ferric reducing antioxidant potential, FW: Fresh weight, GAE: Gallic acid equivalents, NADH: β-nicotinamide adenine dinucleotide hydrate, NFL: The National Food Laboratories, NO: Nitric oxide, ONPG: ortho-nitrophenyl-β-galactoside, PBS: Phosphate buffered saline, PMS: Phenazine methosulfate, QE: Quercetin equivalents, ROS: Reactive oxygen species, SD: Standard deviation, SOD: Superoxide dismutase, TCA: Trichloroacetic acid, TPTZ: 2,4,6-tris(2-pyridyl)-s-triazine, Trolox: (±)-6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid.

Keywords: Antioxidant activity; IC50; flavonoids; phenols; proanthocyanidins; radical scavenging.

Figure 1

Ferric reducing power of fruit extracts. Butylated hydroxyl toluene was used as a standard. Results represent means ± standard deviation of three experiments. Bars for each plant extract with no superscript letters are significantly different from each other at P ≤ 0.01. Bars for each plant extract with * are significantly different from each other at P ≤ 0.05 (Tukey's test)

Figure 2

Ferric reducing antioxidant potential of fruit extracts. Results represent means ± standard deviation of three experiments. Bars with no superscript letters are significantly different from each other at P ≤ 0.01 (Tukey's test). Bars with same superscript letters are not significantly different

Camelia Maier