No abstract

No abstract

No abstract

No abstract

The radical-scavenging activity of vegetables was measured using the 1,1-diphenyl-2-picrylhydrazyl-HPLC method, and the effect of cooking on this activity was determined. The content of ascorbic acid having radical-scavenging activity was highest in burdock among the 18 fresh vegetables tested. In some vegetables, the activity increased in spite of the loss of ascorbic acid content after boiling, while in other vegetables, the activity had decreased after boiling. This decrease may be due to release of the activity from cooked tissue into the cooking water during boiling. Both activity and ascorbic acid content of the vegetables cooked in a microwave were generally higher than in those cooked by boiling.

No abstract

A hydroperoxide (HPO) lyase which catalyzes the specific cleavage of 13-L-hydroperoxy-cts-9,irans-11-octadecadienoic acid (13-L-c,£-HPO) to form n-hexanal was found in the homogenates of the soybeans such as Glycine max var. Suzuyutaka (normal type) and lipoxygenase (L) deficient mutant seeds (L-l null, L-2 null, L-3 null). A carbonyl compound which was formed from 13-L-c,í-HPO and 13-dl-c,£-HPO by the enzyme was n-hexanal. The enzyme was specific to the L isomer of 13-c,í-HPO. 9-D-i,c-HPO was not available for the enzyme reaction. Km and Vmax values of the enzyme for 13-L-c,£-HP0 were apparently similar among all the seeds. Apparent Vzmax value of the homogenate from L-2 null seed for linoleic acid was considerably lower (1/3-1/4) than those in the other seeds. It is concluded that a rate-determining step of n-hexanal formation from linoleic acid in L-2 null seed is a step of 13-L-c,£-HP0 formation by lipoxygenase. cross between P.I. 408251 (L-l null type) and Suzuyutaka. L-2 deficient mutant was a line from the cross between P.I.

The influence of polyphenol oxidase and ascorbate oxidase on radical-scavenging activity and contents of total phenol, chlorogenic acid, and ascorbic acid in vegetables during the cooking process were investigated. In the case of burdock and lettuce, which have a high activity of polyphenol oxidase, the radical-scavenging activity and the content of total phenol and chlorogenic acid decreased drastically within 1 min. In the case of broccoli, however, only a small decrease of radical-scavenging activity was observed, and total phenol and chlorogenic acid decreased almost not at all. The decrease of the activity in broccoli depended on the oxidation of ascorbic acid by ascorbate oxidase. None of these compounds decreased after the enzymes had been inactivated by heating.