Effect of temperature on the antioxidant activities of selected vegetables measured by free radical scavenging, superoxide scavenging and inhibition of lipid peroxidation assays

Date

4-2004

Degree

Bachelor of Science in Biology

Major Course

Major in Cell Biology

College

College of Arts and Sciences (CAS)

Adviser/Committee Chair

Ivan Marcelo A. Duka

Abstract

The free radical scavenging (FRS) activity, superoxide scavenging (SOS) activity and inhibition of lipid peroxidation (ILP) of the water and methanol extracts of drumstick tree (Moringa okiftra), sweet potato (Ipomoea haulms), Chinese ccdrus (Cedrela sinensis), rosemary (Rosmarinus officinalis), and penghu senna (Cassia sophora L var penghuana) leaves subjected to —20°C. 25°C (control), 50°C and 100°C temperature gradients at the Asian Vegetable Research and Development Center were evaluated. For water extracts/methanol extracts, Chinese cedrus leaves (157/546 TEμmole/g) exhibited the highest FRS activity while sweet potato leaves (12/26 TEμmole/g) was the least. For SOS (water extracts), Rosemary (41 ARP) showed the highest value while sweet potato leaves (9 ARP) showed the lowest. For SOS (methanol extracts), Chinese cedrus (111 ARP) exhibited the highest value while rosemary (33 ARP) showed the lowest. Chinese cedrus leaves (491 TEμmolc/g) showed the highest ILP while drumstick tree leaves (45 TEμnole/g) was the least. It was found that generally, methanol extracts have higher antioxidant activity than the water extracts. This result suggests the presence of antioxidant compounds like phenolics and carotenoids that were responsible for the antioxidant activity. For the effect of low temperature, in general, there was a variation in (FRS, SOS and ILP) with an average of 27.2% reduction. In some cases, however, there was a slight 8% increase as compared to the control (25°C). In general, three trends were observed for all antioxidant assays and for both water and methanol extracts. First, there is a significant (p<0.05) increase in the activity (FRS, SOS and ILP) for both treatments in 50°C and 100°C. Second, there is a significant decrease in the activity (FRS, SOS, and ILP) for both treatments in 50° and 100°C. Third, there is significant decrease in activity in the 50°C-treatment while a significant increase in the 100°C treatment (FRS, SOS and ILP). However, these observations or trends are not consistent for any one vegetable studied. Thus. there are evidences to support the possibility of an increase in the antioxidant activity in heat-treated vegetables. This suggests that upon heat treatment, thermal degradation of a plant components release free antioxidants. Alternatively some vegetables have decreased antioxidant activities due to degradation of antioxidants.

Language

English

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

Thesis

Document Type

Thesis

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