II. MARCO TEÓRICO
4. Detentación o tenencia
5.2. Un intento de solución del conflicto en la norma procesal de Tercería de
The leaves both fresh and processed were macerated and extracted with 80% methanol [16] by shaking vigorously for 30 minutes using a cyclo rotator. The sample suspensions were centrifuged at 10000 rpm at 5oC for 20 minutes and the supernatants filtered through wattman filter paper and the extract used for estimation of hydrophilic ORAC, FRAP and TP. To estimate the ORAC value of the lipid soluble fractions, the residue was agitated with acetone, shaken vigorously for half an hour, centrifuged (10000 rpm at 5oC for 20 minutes) and the supernatant used for estimation.
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RESULTS AND DISCUSSION
Total Antioxidant Capacity of fresh leaves
The TAC values by ORAC assay was higher than FRAP assay for all the samples. There was a significant correlation (P<0.01) between the two methods. But the ranking of foods in the order of highest antioxidant capacity was observed to be different in the two methods. For example, fenugreek leaves ranked fourth in ORAC assay whereas it was eighth in FRAP assay. ORAC and FRAP assays have two different principles, the former based on quenching peroxide radical and the later based on the reducing capacity of the compounds and hence variations can be expected. The TAC of fresh leaves(Table I and Table II) ranged from 5248.98 µmol TE/100g to 496.72 µmol TE/100g by ORAC assay and 4419.4 µmol TE/100g to 374.97 µmol TE/100g by FRAP assay. In both assays curry leaves had the highest antioxidant capacity and spinach had the least. The amaranth varieties ranked second and had higher TAC values than drumstick, coriander, mint and fenugreek leaves. Curry leaves have also been reported to have comparatively the highest antioxidant capacity by other antioxidant assays [17].
TAC of Dried and Steamed leaves
The dried samples had significantly higher TAC values by both ORAC and FRAP assay than fresh and steamed leaves (Table I and Table II) except for spinach leaves. Steamed spinach leaves did not have a higher value than fresh leaves but dried spinach leaves had. Cooking with excess water, boiling and blanching reduces the antioxidant capacity while sautéing and steaming at atmospheric and high pressures increases the antioxidant capacity [18].
Among steamed leaves Mint and Amaranth leaves had the highest antioxidant capacity followed by curry leaves. The TAC values (ORAC) of steamed Mint leaves was seven times more than fresh leaves.
Among dried samples(Table I and Table II), dried Curry leaves had the highest antioxidant capacity in both ORAC and FRAP assay, 22471.46 µmol TE/100g and 14448.9 µmol TE/100g respectively. The dried leaves had very high TAC values, the TAC value of dried Solanum leaves being 18 times more than fresh leaves.
TOTAL PHENOLS
Among fresh leaves, Curry leaves had the highest phenolic content of 703.42 mg GAE/100g and Mint leaves had the least total phenols of 154.01 mg GAE/100g (Table III). Curry leaves have been studied to be rich in phenolics. The major phenolic constituents in curry leaves include myricetin-3-galactoside, quercetin-3-rutinoside, quercetin-3-glucoside, kaempferol-3-O- caffeoylate, isorhamnetin-3-O-glucoside and 5-caffeoyl quinic acids[19].
Steaming substantially increased the phenolic content of all the leaves except in curry leaves and spinach. The phenolic content of steamed curry leaves was 1.5mg less than fresh leaves. The phenolic content of steamed spinach leaves was marginally higher, by 8.29mg, than fresh leaves. Steamed mint leaves had the highest phenolic content of 785.4 mg GAE/100g.
Dried fenugreek leaves had a lower phenolic content then fresh leaves while all the other samples had higher values than fresh leaves. A study on the effect of sun drying on the antioxidant and phenolic contents has also revealed a significant increase in the total phenol content (6.45-223.08 percent gain), reducing property (16.00-362.50 percent gain) and free
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radical scavenging ability (126.00-5757.00 percent gain) of the green leafy vegetables but a significant decrease in vitamin C content[20].
Effect of processing on the TAC and TP content
The effect of drying and steaming on the TAC and TP content was analysed after correcting for gain or loss in moisture after steaming and drying. Table IV depicts the effect of steaming and drying on TAC by FRAP analysis. A very high increase in TAC values was observed after steaming in all the leaves except Spinach leaves in which the TAC decreased by 9.9µmols TE. The TAC values of Mint leaves increased from 922.57 µmol TE/100g to 7238.03 µmol TE/100g, while the TAC of Amaranthus varieties increased on an average by 4182.3 µmol TE/100g. On the contrary, drying resulted in a high loss of TAC in all the leaves. The loss varied from 65 percent in spinach leaves to 92 percent in curry leaves. Steaming increased the TAC of leaves at a higher percentage than FRAP analysis.
Steaming and drying decreased the TP values of curry leaves by 68.95mg GAE/100g and 645.03 mg GAE/100g respectively.
Contribution of Total Phenols to Total Antioxidant Capacity
The phenol constituent of the green leafy vegetables contributes more to the antioxidant properties of vegetables than ascorbic acid [21]. A wide variation was observed among the leaf varieties in the contribution of phenols to total antioxidant capacity.
The highest contribution was observed in fresh leaves where the percentage contribution ranged from 38.7 in Drumstick leaves to 13.2 in Mint leaves by ORAC assay and 55.3 percent in drumstick leaves to 13.5 percent in coriander leaves by FRAP assay(Figure II).
Both steaming and drying decreased the contribution of phenols to TAC, indicating a loss during processing. The margin of decrease varied considerable among the leaves. The percentage contribution of phenols decreased from 17.3 percent to 7 percent after steaming and 6.2 percent after drying in Amaranthus G. leaves, whereas the phenolic contribution decreased from 38.7 percent to 33.1 percent after steaming and to 5.6 percent after drying in drumstick leaves by ORAC assay. Similar variations were observed in FRAP assay as well.
CONCLUSION
Green leafy vegetables are rich source of antioxidants. All the varieties of green leaves selected showed a high level of antioxidant capacity by both ORAC and FRAP assays and are rich in phenols. Steaming and drying have a profound influence on the antioxidant content of the leaves. All leaves showed a significant increase in antioxidant capacity and total phenols after steaming and drying with a few exceptions like spinach and curry leaves. The total phenolics in leaves also showed a significant increase after steaming and drying, but for curry leaves whose phenolic content decreased after steaming. There are wide variations in the contribution of phenols to TAC in fresh leaves and in the contribution of phenols to TAC after drying and steaming indicating a change in the antioxidant profile after processing. Evaluating the effect of the chosen processing methods steaming would be the ideal method for processing green leafy vegetables.
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