Influences of leaf pruning on the content of the secondary phenolic metabolites barbaloin, aloeresin and aloenin, in the leaves of Aloe arborescens

The content of three secondary phenolic metabolites (SPMs) barbaloin, aloeresin and aloenin, in Aloe arborescens is the highest in leaf two. The lower the leaf on the branch, the lower is the content of SPMs. The content of SPMs also differs in the various parts of each leaf. The highest amounts are found along the margins of the upper third of the leaf and the lowest at the centre of the leaf base. After pruning a leaf, the SPMs content in the regrown part of that leaf is higher than in another plant with unpruned leaves. Repeated leaf pruning can gradually increase the SPMs content of the dry exudate of regrown parts from 12-86%. The higher the pruned leaf is on the branch, the greater the increase in the content of SPMs in the regrown parts of the leaf. Such leaf pruning also increases the content of SPMs in the leaf located opposite the pruned leaf, but a greater increase occurs in the new young leaf at the top of the branch. Pruning leaf two gradually increases the content of SPMs in the lower leaves. The higher the leaf, the greater the increase.