Effects of gamma irradiation on antioxidant potential and chemical composition of Ginkgo biloba L.: a comparative study of 1 and 10 kGy doses
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abstract
Ginkgo biloba L. is a very old tree widely used in pharmaceutical industry to combat some diseases;
in particular, is has been experimentally used as a natural therapeutic agent in the treatment of
Alzheimer's disease [1,2]. Irradiation is a methodology accredited for dry ingredients, being
increasingly recognized, and represents almost 50% of the world market for post-harvest preserved
foods (~186 000 ton). Furthermore, irradiation might also represent a suitable solution for medicinal
plants postharvest treatment in order to guarantee their decontamination [3,4,5]. In this study, the
effects of gamma irradiation (1 and 10 kGy) in the antioxidant properties and chemical composition
of G. biloba were evaluated. Radical scavenging activity, reducing power and inhibition of lipid
peroxidation in brain homogenates were used to evaluate antioxidant potential. Macronutrients
(protein, fat, carbohydrates and ash) were determined following official procedures of analysis;
hydrophilic (sugars and organic acids) and lipophilic (fatty acids and tocopherols) compounds were
determined by chromatographic techniques coupled to different detectors. In general, the methanolic
extract gave higher antioxidant activity (lower EC50 values) than the corresponding infusions. For
both infusion and methanolic extract, gamma irradiation at both doses increased 2,2-diphenyl-1-
pycrilhydrazil (DPPH) scavenging activity, reducing power, β-carotene bleaching and lipid
peroxidation inhibition of Ginkgo samples. In chemical composition this process preserved
macronutrients (ash, fat and energy were not changed), fatty acids, γ- and δ-tocopherols, fructose,
trehalose, quinic and shikimic acids. In particular, 1 kGy protected α-tocopherol, oxalic and malic
acids contents, while 10 kGy decreased proteins, α-tocopherol, glucose, sucrose, oxalic and malic
acids level. Overall, irradiation at 10 kGy potentiated more the antioxidant activity of methanolic
extract and infusion obtained from leaves and 1 kGy would be the recommended dose to maintain
nutritional profile of G. biloba, protecting specific molecules.
The authors are grateful to PRODER nº 53514, AROMAP, for financial support of the work and E. Pereira
grant, to Mrs. Clarinda Paixão, from Américo Duarte Paixão Lda, for samples providing and to FCT for
financial support to CIMO (PEst-OE/AGR/UI0690/2011) and L. Barros (Compromisso para a Ciência 2008).
