| Summary: | 碩士 === 南華大學 === 自然生物科技學系自然療癒碩士班 === 103 === Background and Purpose: Vernonia amygdalina (VA), known as bitter leaf, is a valuable medicinal plant. Besides its use as a vegetable, the plant is also used in the treatment of malaria, diabetes, diarrhea, venereal diseases, hepatitis, gastrointestinal problems, skin diseases and wounds. The aim of this study is to investigate the antioxidative properties of V. amygdalina and how it could be used to reduce oxidative damage in the body.
Methods: V. Amygdalina leaves and stems were extracted using three different solvents: water, ethanol and ethyl acetate. The following antioxidative activity assays were conducted: α,α-diphenyl- β-picrylhydrazyl (DPPH) radical scavenging ability, Fe2+ chelating ability, relative reducing power, and superoxide anion scavenging ability. The different extracts were evaluated for angiotensin I-converting enzyme inhibitory (ACEi) activities and active ingredient contents, which included flavonoids, total phenolics, anthocyanins and amino acids.
The results:
1. The aqueous extracts from VA leaves and stems had the highest content (24.9 and 27.2 %, respectively).
2. The antioxidant activities for the VA extracts obtained were as follows: the ethanolic extract (stem higher than leaf, EC50 values were 0.52 and 0.78 mg/mL, respectively) had the highest DPPH radical scavenging ability compared to the ethyl acetate and water extracts. The ethanolic extract had the highest Fe2+ chelating ability (leaf higher than stem, EC50 values were 0.77 and 0.90 mg/mL, respectively), and the ethyl acetate extract from the leaves had the lowest antioxidant capacity. The highest reducing power was detected in the ethanolic extract. Results showed that stems had better ability than leaves in all extractions, with the ethyl acetate extract of stems showing the best superoxide anion scavenging ability (EC50 value was 0.94 mg/mL).
3. The active ingredient content of VA extracts obtained was as follows: the aqueous extracts from VA leaves and stems contained high level of anthocyanins, with the highest concentration found in the leaf extracts (1.51 μmole/g). The aqueous extract had the highest total phenolics content (687.31 μg/mg) (leaf higher than stem), followed by the ethanol and ethyl acetate extracts (111.15 and 49.62 μg/mg, respectively). Similar flavonoid content was detected in the ethanol and ethyl acetate extracts (the highest concentration (29.26 μg/mg) was detected in the ethyl acetate extract of stems), and the lowest content was found in the aqueous extract. The highest amount of amino acids was detected in the aqueous extract of leaves and stems, while the ethyl acetate extract had the least content.
4. ACE-inhibitory activity of the aqueous extract from the leaves and stems had strong inhibitory activity (0.19 and 0.82 mg/mL, respectively) and the ethanol stem extract had the lowest activity.
Conclusion: The ethanolic extract had the highest antioxidant activity, including DPPH, ferrous ion chelating and reducing power. In addition, both the leaves and stems extracts were found to have good antioxidative capacities. The aqueous extract of VA leaves contained the highest levels of anthocyanins and total phenolics. Flavonoid contents in the ethanolic and ethyl acetate extracts were almost the same. A variety of amino acids was present in the aqueous extract, and its concentration was higher than the other extracts. Aqueous extracts were found to have strong ACEi activities. In summary, leaf and stem extracts of VA showed antioxidant activities. In all the solvents that were used to extract VA, the aqueous and ethanolic extracts were found to have the highest antioxidant activities and active components.
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