Cytogenotoxic effects of 3-epicaryoptin in Allium cepa L. root apical meristem cells

Diterpenoid 3-epicaryoptin (C₂₆H₃₆O₉) is abundant in the leaves of Clerodendrum inerme, a traditionally used medicinal plant, and has insect antifeedant activities. Here, we aim to explore the cytogenotoxic effects of compound 3-epicaryoptin in Allium cepa root apical meristem cells. 3-epicaryoptin (concentrations of 100, 150, and 200 µg mL^-1) and the standard compound colchicine (200 µg mL^-1) were applied to A. cepa roots for 2, 4, and 4 + 16 h (4-h treatment followed by 16-h recovery). Cytogenotoxicity was analyzed by studying the root growth retardation (RGR), mitotic index (MI), and chromosomal aberrations. The result showed statistically significant (p < 0.01), concentration-dependent RGR effects of 3-epicaryoptin treatment compared with the negative control. A study of cell frequency in different phases of cell division observed a significant (p < 0.001) increase in the metaphase cell percentage (66.2 ± 0.58%, 150 µg mL^-1), which subsequently caused an increase in the frequency of MI (12.29 ± 0.34%, 150 µg mL^-1) at 4 h of 3-epicaryoptin treatment and that was comparable with the colchicine action. The cytological study revealed that the 3-epicaryoptin treatment could induce different types of chromosomal abnormalities, such as colchicine-like metaphase, vagrant chromosomes, sticky chromosomes, anaphase bridge, lagging chromosomes, multipolar anaphase-telophase, and an increased frequency of micronuclei and polyploid cells. These findings indicate that 3-epicaryoptin is cytogenotoxic, and thus, C. inerme should be used with caution in traditional medicine.