Abstract

Common buckwheat (Fagopyrum esculentum Moench) and tartary buckwheat (Fagopyrum tataricum L. Gaertn) were used as materials to study plant self-defensive strategies against oxidative stress and pathogen infection during seed germination. Sprout development induced hull structure split, membrane degradation and tissue injury, accompanied with production of a large amount of reactive oxygen species (ROS) such as superoxide (O₂^-)_, hydroxyl radical (·OH), alkoxyl radical (R·) and hydrogen peroxide (H₂O₂). Therefore, buckwheat sprouts had to face both oxidative stress and environment pathogen aggression during the course of malting. To analyze the antioxidant capacity of ROS by buckwheat seeds, the activity of four kinds of antioxidant enzyme was studied, including superoxide dismutase, catalase, peroxidase and ascorbate peroxidase. Scavenging effects of 2, 2-diphenyl-1-picrylhydrazyl free radicals were also investigated. Both gram-positive bacteria (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli, Salmonella typhimurium and Bacillus subtilis) were applied to detect antibacterial activity of the germinated seeds against microorganism pathogen infection. Ethanolic extracts of flavonoids from germinated seeds revealed an obvious anti-tumor activity against human lung carcinoma cell line by MTT  assay. Our research in this paper indicated that through long term evolution, buckwheat had already developed advanced strategies to repair inner injury and to resist the outer environmental risks during seed germination. The enriched production of flavonoids in the germinating stage might quite possibly be applied in clinical field to deal with lung cancer.

Key words: Common buckwheat, tartary buckwheat, germinated sprout, antioxidant activity, antibacterial activity, antitumor activity, lung cancer.

Abbreviation

ROS, Reactive oxygen species; SOD, superoxide dismutase; CAT,catalase; POD, peroxidase; ASP, ascorbate peroxidase; 2, DPPH•, 2-diphenyl-1-picrylhydrazyl; BWAEs, buckwheat antioxidant enzymes; BWFEs, buckwheat flavonoid extracts.