In Vitro Anti-Cancer Analyses of Selected Apocynaceae Family Species From Sri Lanka

Background: According to the World Health Organization around 65% of the world's population rely on traditional medicines derived from plants for their primary healthcare needs. Plants have been used as medicines for many number of years. Sri Lanka has a rich traditional medicine history of around 3000 years and has an ample amount of plants being a tropical island. Sri Lanka has around 1430 medicinal plant species and number of these species have been used for cancer therapy by traditional medicine practitioners in the country. The cancer incidence in Sri Lanka is rising due to population aging, various life style factors such as westernized diets, smoking and lack of physical activity. Thus preventive measures such as various kinds of anticancer foods should be introduced. Aim: Tabernaemontana divaricata (TD) and Plumeria rubra (PR) which belong to the Apocynaceae family of plants and they are commonly found in Sri Lanka and they were tested to determine their anticancer activity. Methods: Leaves and stems of the plants were collected from Colombo district Sri Lanka. Ethical approval was obtained from the Department of Forest, Sri Lanka. Finely dried leaves and stems were subjected to ethanol extractions. MTT, clonogenic, cell cycle, apoptosis, gamma H2AX, cell migration, reactive oxygen species (ROS), environmental scanning electron microscopy (ESEM) were used to determine anticancer activity. Results: HER2+ SKBR3 cell line showed the best sensitivity to both plants among a panel of breast cancer cell lines. TD-GI 50 leaf extract: 6.89 µg/mL ± 1.72; stem extract: 12.49 µg/mL ± 4.04) and PR-GI50 leaf extract 17.45 µg/mL ± 2.05; stem extract was not active. Clonogenic assays showed low colony formation for all active extracts in SKBR3 cells ( P ≤ 0.001). All extracts caused G1 arrests in cell cycle analysis compared with SKBR3 control ( P ≤ 0.0001). Minor amounts of apoptotic populations were observed with extracts compared with SKBR3 control ( P ≤ 0.01). Further, both leaf extracts caused minor amounts of DNA double strand breaks by gamma H2AX analysis in SKBR3 cells ( P ≤ 0.05). All extracts showed low SKBR3 cell migration ( P ≤ 0.0001). Both leaf extract were able to generate high levels of ROS in SKBR3 cells ( P ≤ 0.001). ESEM demonstrated morphologic differences in TD leaf extract treated SKBR3 cells. Conclusion: These results are promising and shows anticancer activity. Chemical compounds are being isolated from these plants. Sri Lanka is yet to develop anticancer drugs from its natural products, and these plants can be a stepping stone in the quest of finding novel therapies for cancer from Sri Lanka. Further, these results can be used to develop cancer preventive food supplements as well since the number of cancer cases are rising in the country.