Studies on the biosynthesis of sym-homospermidine in sandal (Santalum album L.)

The biosynthesis of the newly isolated polyamine, sym-homospermidine (NH2–[CH2]4–NH–[CH2]4 –NH2), was studied by using radioactive amino acids. Arginine was the most effective precursor, being about 10 times as active as ornithine. Unlabelled agmatine and putrescine markedly inhibited the incorporation of [14C]arginine into homospermidine. Similarly the incorporation of ornithine was inhibited by unlabelled arginine and putrescine. γ-Aminobutyraldehyde, the oxidation product of putrescine, was considered to be one of the intermediates in the biosynthesis of homospermidine. The biosynthesis may involve a Schiff-base formation of putrescine with γ-aminobutyraldehyde and subsequent reduction. A limited synthesis of spermidine also takes place under these conditions.