Dietary phenolic phytochemicals of "Gabi" (Colocasia esculenta, Linn.) leaves: profile, antioxidant and angiogenic activities

Date

4-2005

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Evelyn B. Rodriguez

Abstract

RETIRO, YAZMINE ANDANG. College of Arts and Sciences, University of the Philippines Los Banos. April 2005. Dietary Phenolic Compounds of "Gabi" (Colocasia esculenta, Linn.) Leaves: Profile, Antioxidant and Angiogenic Activities

ADVISER: Dr. Evelyn B. Rodriguez, Ph.D.

Phenolic compounds from fresh leaves of "gabi" (Colocasia esculenta, Linn.) were isolated in three ways: extraction with 7:7:6 methanol-acetone-water (MAW); extraction with 60% methanol, followed by hydrolysis with IN HCI; and saponification of the MAW extract with 4N NaOH. The profiles of the phenolic extracts were determined employing a descending two-dimensional paper chromatography technique. The phenolic components were identified or classified into compound types based on their retardation factor in paper chromatography and color manifested under visible and UV light, boils in the presence and absence of ammonia. The major components were eluted from paper with 70% methanol and rechromatographed with standards and subjected to UV spectral analysis. Quercetin-3-0-glucoside was the major component of the MAW extract, while those of the acid- and base-hydrolyzed extracts were quercetin and caffeic acid, respectively.

The total phenolic contents of the extracts were determined using the FolinCiocalteau reagent and gallic acid and catechin as standards. The MAW extract contained 1131 mg GAE/kg fresh sample and 2026 mg CE/kg fresh sample. The acid-hydrolyzed extract had 784 mg GAE/kg fresh sample and 1269 mg CE/kg fresh sample, while, the base-hydrolyzed extract had the lowest total phenolic content (597 mg GAE/kg fresh sample and 896 mg CE/kg fresh sample).

The antioxidant activity of different concentrations of the MAW extract was evaluated by measuring the inhibition of 'MARS formation in lecithin liposome oxidation and calf thymus DNA oxidation. At 20 ppm the extract inhibited 47.4% of TEARS formation in lipid peroxidation; under the same conditions BHT effected 71.1% inhibition, while quercetin and caffeic acid caused 68.4% and 39.5% inhibition, respectively. In the DNA oxidation, :he 8 ppm extract exhibited the highest activity (47.3%), followed by quercetin (45.9%), caffeic acid (43.2%) and BHT (41.1%).

The free radical scavenging of the extract, at different concentrations (50, 100, 200, 300 ppm) was measured using the DPPH radical. The highest radical scavenging activity of the extract was exhibited at 300 ppm (63.6%); under the same conditions, both quercetin and caffeic acid had 98.6% activity, white BHT had only 25.17%.

The MAW extract was also evaluated for its angiogenic using the duck embryo assay. Different concentrations (400, 800, 1200 ppm in PBS) of the extract and of the reference compound caffeic acid, were introduced into 14-day old duck embryo after five days of incubation, evident suppression of blood vessel formation was seen in the extract-treated embryo, at 800 to 1200 ppm. The caffeic acid-treated embryo had evident suppression only at 1200 ppm.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2005 C4 R48

Document Type

Thesis

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