Phenolic profile, antioxidant, free-radical scavenging and angiogenic activity of "sibuyas tagalog" (Allium ascalonicum, Linn.)

Date

4-2004

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Evelyn B. Rodriguez

Abstract

REYES, CHARIS TONGSON. College of Arts and Sciences, University of the Philippines Los Banos. April 2004. Phenolic Profile, Antioxidant, Free-Radical Scavenging and Angiogenic Activity of `Sibuyas Tagalog' (Allium ascalonicum , Linn.).

ADVISER Dr. Evelyn B. Rodriguez, Institute of Chemistry

Phenolic compounds were extracted from fresh samples of `sibuyas Tagalog' (Allium ascalonicum, Linn.) using methanol-acetone-water (7:7:6) solution. The composition of the phenolic extract was determined by descending two-dimensional paper chromatography using n-butanol-acetic acid-water (6:1:2) for the first dimension and 15% acetic acid for the second. The phenolic profile showed 9 components which were classified into compound types through their chromatographic mobilities, color under ordinary and UV light and color of their charge-transfer complexes with ammonia. The major components were eluted from paper and were identified as the flavonols quercetin and kaempferol through their visible spectra and comparison with standards and literature data. The total phenolic content was determined by the Folin-Ciocalteu reagent using catechin as standard; the extract contained 336 mg catechin/kg sample.

The antioxidant activity of different concentrations of the extract (200, 600, 1000, 2000 ppm) was evaluated on the autooxidation of corn oil. The antioxidant activity was measured by the determination of the peroxide value and thiobarbituric acid (TBA) assay. A parallel study on antioxidant activity of butylated hydroxy toluene (BHT), the most commonly used antioxidant, was conducted for comparison. From the measurement of peroxide value of corn oil, it was shown that the antioxidant activity: at 30 days the corn oil containing 2000 ppm extract had a peroxide value of 3.380 mg peroxide/kg oil while the control had a peroxide value of 10.400 mg peroxide/kg oil. Corn oil containing 200 ppm BHT gave a peroxide value of 3.820 mg peroxide/kg oil under the same conditions. Consistent with the results on lipid hydroperoxide inhibition, the extract with the highest concentration (2000 ppm) effected the highest inhibition of malonaldehyde production in the TBA assay. At 25 days of incubation of 2000 ppm extract gave a TBA number of 0.993 mg malonaldehyde/kg oil, while for the control and 200 ppm BHT, the TBA numbers were 1.131 and 1.124 mg malonaldehyde/kg oil, respectively.

The free-radical scavenging activity of the extract was measured by its kinetic behavior towards 2,2-dipheny1-1-picrylhydrazyl (DPPH'). The antiradical efficiency (AE) of the extract and quercetin were 0.081 x 10'3 and 0.21 x 1 0-3, respectively. The values are classified as low free-radical scavenging activity and are consistent with those reported in the literature for phenolic compounds.

Angiogenic activity of the extract was studied using the duck embryo assay. Different concentrations of the extract (600, 1200, 4000 ppm) were introduced into 14-day old duck embryo. Results after four days of incubation showed that both the number and size of blood vessels of embryos treated with the extract were significantly reduced compared to the control. Extreme angiostatic effect caused the death of the embryo in the presence of concentrated extract. The results demonstrated that the phenolic extract was a potent anngiogenesis inhibitor at all concentrations. In a parallel study, it was observed that quercertin was as potent angiogenesis inhibitor as the extract.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2004 C4 R49

Document Type

Thesis

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