Proximate analysis of Laurencia sp., partial characterization and evaluation of the antioxidant properties of its methanolic extract

Date

10-2013

Degree

Bachelor of Science in Chemistry

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Hidelisa P. Hernandez

Restrictions

Restricted: Not available to the general public. Access is available only after consultation with author/thesis adviser and only to those bound by the confidentiality agreement.

Abstract

Proximate analysis showed that fresh Laurencia sp. is composed of 86.86% moisture, 0.8111% crude fat, 0.9155% crude fiber, 0.5164% crude protein and 4.120% ash. Mineral analysis of Laurencia sp., on the other hand, resulted in 50.55 ± 4.24 mg P/100 g and 1903 ± 20 mg Na/100 g. Surface extraction of Laurencia sp. with hexanes yielded an extract which was 0.0003% of the sample. Thin layer chromatography (TLC) of the surface extract using hexanes produced two spots, SE 01 (Rf = 0.11) and SE 02 (Rf = 0.49). 2.7:0.3 (v/v) hexanes/ethyl acetate yielded two spots, SE 03 (Rf = 0.15) and SE 04 (Rf = 0.59). Using 1.8:1.2 (v/v) hexanes/ethyl acetate, eluted all the spots to the solvent front. 1H NMR data of the surface extract showed that the compounds have hydrogens on aromatic rings, alpha-H in alcohols and carbonyls, alkyl groups, allylic groups, vinylic groups, ethers and esters. Whole plant extraction with methanol produced 0.0058% extract, fresh weight basis. The methanolic extract was subjected to column chromatography using hexanes and hexanes/ethyl acetate solvent systems. TLC was used for the identification of spots contained in each eluted fraction. GC-MS analysis of LP 01, which was eluted with hexanes, gave the possible identification of three compounds (Z)-2-decenal, 10-undecenal and 2,4-decadienal. Fraction eluted with hexanes/ethyl acetate (9:1) produced three spots, LP 02, LP 03 and LP 04. 1H NMR analysis of LP 02 and LP 03 both showed that the compounds have hydrogens coming from alpha-H in alcohols and carbonyls, alkyl groups, allylic groups, alkynyl groups, ethers and esters. However, LP 03 shows additional signals showing protons coming from vinylic groups, aldehydes and aromatic compounds. GC-MS analysis of LP 04 gave the possible identification of hexadecanoic acid and 6-octadecenoic acid as its main components. The methanolic extract showed lower concentration-dependent activity against DPPH radical and H2O2 compared to ascorbic acid, the same with iron chelating activity compared with EDTA. . On the other hand, the methanolic extract has comparable activity at 1250 to 5000 ppm with ascorbic acid on hydroxyl radical scavenging assay.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 993.5 2013 C42 /C78

Document Type

Thesis

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