Antimitotic effect, G2/M accumulation, chromosomal and ultrastructure changes in meristematic cells of Allium cepa L. root tips treated with the extract from Rhodiola rosea roots

Rhodiola rosea is a Russian and Chinese medicinal plant used in medical practice as a stimulating, adaptogenic and antiarrhythmic agent. Many investigations have pointed to the anticancer and antimutagenic role of R. rosea. In spite of these therapeutic effects of R. rosea extract, little is known about the mechanism of its anticancer action, because few cytological investigations have been conducted on the mitotic activity, cellular cycle, structure, ultrastructure, and cytophysiology of both animal and plant cells treated with the extract. Our studies have shown that extract from R. rosea roots (containing rosavine and cinnamyl alcohol) cause the inhibition of a mitotic activity; however, cells resume their divisions after the postincubation period. During incubation in the extract, accumulation of G2/M cells was observed. Chromosomes in prophase and metaphase were shorter and thicker but the extract did not cause chromosomal aberrations or the formation of micronuclei. Ultrastructure changes after 24 h of incubation were connected with an increase in the electron density of ground cytoplasm, decrease in the number of mitocbondria but with an increase of their surface. As early as after 6h postincubation, the number of mitochondria doubled but their surface declined by over two times. After 24 h of incubation, the surface of plastids increased over twice in spite of their unchanged number. In postincubation (6h), their number doubled and the surface declined dramatically. The ultrastructure of the mitochondria was changed by the disappearance of cristae and a lowered electron density of the matrix, suggesting that one of the mechanisms could be connected with changes in mitochondrial function.