Determination of endogenous formaldehyde in plants (fruits) bound to L-arginine and its relation to the folate cycle, photosynthesis and apoptosis.

A very powerful nucleophilic reagent, hydralazine(1-hydrazino-phtalazine) proved to be suitable for determination of the endogenous formaldehyde level in biological samples. It was found that in different plants (vegetables, fruits, especially in red beet, cauliflower, kohlrabi, grapes) is a large amount of releasable endogenous formaldehyde (0.5-1.0 mM) bound to L-arginine mainly in the form of N(G)-trihydroxymethyl-L-arginine (TriHMA). N(G)-hydroxymethyl-L-arginines (HMA) were proved to transfer their hydroxymethyl groups to tetrahydrofolic acid producing N5,N10-methylene-tetrahydrofolate, the coenzyme of thymidylate synthase. HMA was found to inhibit the cell proliferation of HT-29 cell culture (human colon adenocarcinoma ATCC HT-B 38) causing apoptosis. Photosynthetic experiments produced confirmatory evidences that 14CH2O could be formed in photosynthesis already after 10 seconds of 14CO2 fixation in the seedlings of Zea mays L. (single cross) and the 14CH2O was immediately trapped by L-arginine mainly as TriHMA.