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, having insect antifeedant activities. Here, we aim to explore the cytogenotoxic effects of compound 3-epicaryoptin in Allium cepa root apical meristem cells. A. cepa roots were treated with 3-epicaryoptin (100, 150 & 200 g mL-1 concentration) and the standard compound colchicine (200 g mL-1 concentration) for 2, 4, 4+16 h (4 h treatment followed by 16 h recovery). Cytogenotoxicity was analysed by studying the root growth retardation (RGR), mitotic index (MI), and cellular aberrations. The result showed statistically significant (p<0.01), concentration-dependent RGR effects of 3-epicaryoptin treatment compared with the negative control. 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 g mL-1) and which subsequently caused an increase in the frequency of MI (12.29{+/-}0.34 %, 150 g mL-1) at 4h 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, 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.