RADIATION AND PHYTOCHEMICAL PRODUCTION. By Maria Alexandra Moreno

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1 RADIATION AND PHYTOCHEMICAL PRODUCTION By Maria Alexandra Moreno College Station, April 2002

2 BACK GROUND Flavonoids are natural constituents in plant foods and important components in human diet Studies have started to investigate the relationship between diet and cancer It has been found that polyphenol flavonoids exhibit a wide range of biological, pharmacological and chemo protective proprieties Flavonoids act as a free scavengers preventing oxidation and cancer initiation.

3 Irradiation and Phitochemical Production Quercetin,one of the most abundant flavonoids,can act increasing the inactivation and excretion of carcinogens or by reducing oxidative damage of DNA target cells Irradiation has been applied for extending the post-harvest life of fruits and vegetables Previous studies reported that gamma irradiation influences the flavonoid content in fruits and the polyphenolic compounds in mushrooms.

4 FLAVONOIDS Polyphenolic compounds Common flavon nucleus Composed of benzene rings Ubiquitous in plants (flavonols, flavanones, flavanols and flavans) Quercetine present in tea, coffee,cocoa,cereal, grains and a variety of fruits and vegetables.

5 FLAVONOIDS Anthocyanins are other group of flavonoids which are responsible to pigmentation in some fruits and vegetables. Their biosynthesis are other flavonoids and phenolic acids that are also antioxidants. The average intake of flavonoids is about 1g, of this about 170 mg are counted for flavones and flavonols.

6 Antioxidant Activity of Flavonoids Flavonoids show cancer chemo preventive effects because their antioxidant propriety. They act as a scavengers of the oxygen free radicals resulting of the lipid peroxidation and oxidized DNA base,whose reactions are important in the pathogenesis of cancer, and can cause damage at this molecules. The position and the number of hydroxyl groups in flavonoids are responsible of their antioxidative activity.

7 Effect of Irradiation on Flavonoids The effectiveness of irradiation in the preservation of fruits and vegetables differs according to the specie. Some of the changes are associated with the alteration in some enzymatic activities. The formation of flavonoids requires light stimulus, which induces the enzymes responsible of flavonoid biosynthesis,and provides the various substrates for the rapid production of flavonol glucosides. Irradiation emits its effect at some metabolic prior to flavonoid synthesis.

8 Biosynthesis of Flavonoids The phenylalanine ammonia lyase (PAL) catalyzes the phenoylalanine to 4-coumaroyl4 coumaroyl-coa and then it is converting to flavonol end products.

9 Effect of gamma irradiation in fruits and vegetables PRODUCT DOSE (kgy) SOURCE OTHER CONDITIONS ONIONS(red,yellow,pink,and white) Cobalt-60 Storage at C/24 hr HPLC Analysis (determination flavonoids). CITRUS CLEMENTINA 0.3 Cobalt-60 Dose rate = 6 kgyh-¹ Storage at 3-4 C/49 days HPLC analysis. GRAPE POMACE Cobalt-60 Dose rate = 4.5 kgyh-¹ Storage at 4 C/17 days One sample with metabisulfite ph differential method (concentration of anthocyanin)

10 Effect of Gamma Irradiation In diced onions the aglycon content and quercetin content increase in all genotypes,except in white,at both doses. The higher increase was at 0.8 kgy.. Diced onions Dose Aglycone Quercetin Total Red onions Pink onions Yellow onions White onions 0.00 ND ND 0.80 ND ND 0.14 Effect of gamma irradiation on aglycone and total quercetin (mg/kg fresh wt)

11 Effect of Gamma Irradiation There is a higher increase in aglycon content than quercetin content after radiation. Figure 4. Aglycone Content in Irradiated Diced Onions Doses (Kgy) Aglycone( mg/kg fresh wt) Red Pink Yellow White

12 Effect of Gamma Irradiation Figure 5. Total Quercetin Content in Irradiated Diced Onions Doses (Kgy) Total Quercetin (mg/kg fresh wt) Red Pink Yellow White

13 Effect of Gamma Irradiation In whole onions bulbs all genotypes showed an increase in quercetin content at both doses,but the higher increase was at 0.8 kgy. Aglycon content increase slightly after radiation. Whole onions Bulbs Dose Aglycone Quercetin Total Red onions Pink onions Yellow onions White onions 0.00 ND ND Effect of gamma irradiation on aglyconcontent and total quercetin(mg/kg fresh wt)

14 Effect of Gamma Irradiation All genotypes showed an increase in quercetin content at both doses,but the higher increase was at 0.8 kgy. Figure 6.Aglycone Content in Irradiated Whole Onions Bulbs Doses (Kgy) Aglycone( mg/kg fresh wt) Red Pink Yellow White

15 Effect of Gamma Irradiation Figure 7. Total Quercetin Content in Irradiated Whole Onions Bulbs Doses (Kgy) Total Quercetin (mg/kg fresh wt) Red Pink Yellow White

16 Effect of Gamma Irradiation In the case,of Citrus clementina,the results showed an increase in the total phenolic compounds, with a maximum content of 21 days of storage. The PAL activity was significantly higher in irradiated samples compares with control samples.

17 Effect of Gamma Irradiation In the case of grape pomace,, irradiation increased the anthocyanin content, and the best concentration was obtained at 6 kgy dose, and adding sulfite.

18 CONCLUSION Gamma irradiation both low (0.8,1.2, and 3.0 kgy) ) and high doses (6 kgy) ) in combination with lower temperature, improves the flavonoids content in fruits and vegetables by the induction of chemical changes stimulated by the PAL activity in the biosynthesis of this compounds. This increase can be beneficial considering the chemopreventive effects of these flavonoids implicated as dietary antioxidants in foods, and also important for extending the storage time.