Isolation of a new cytotoxic compound, 3-((Z)-heptadec-14-enyl) benzene - 1-ol from Rhus natalensis root extract

•The new compound, 3-((Z)-heptadec-14-enyl) benzene -1-ol was isolated from root extract of R. natalensis.•The ethyl acetate extract of R. natalensis revealed toxicity on HeLa cancer cells with an IC50 17.17 ± 3.45 μg/mL.•Ethyl acetate extract of R. natalensis, significantly induced apoptosis and caused arrest of cell cycle progression.•Ethyl acetate extract of roots of R. natalensis revealed a concentration dependent increase of antioxidant activity.•Ethyl acetate roots extract of R. natalensis was more toxic to brine shrimp larvae (LC50 = 7.25 μg/mL) compared to a known anticancer drug cyclophosphamide (LC50 = 16.12 μg/mL). R. natalensis.Bernh ex C.Krauss (Anacardiaceae) is used by Traditional Health Practitioners (THPs) in Same district, north eastern Tanzania, for treatment of cancer and other diseases. The current study was done to determine its cytotoxic activity. Dried root powder was extracted by cold maceration with a 1:1 mixture of methanol and dichloromethane. Sequential VLC fractions (Petroleum ether, ethyl acetate, and methanol) of the extract were made and tested for toxicity against brine shrimp (Artemia salina) larvae. The ethyl acetate fraction, which exhibited the highest toxicity against brine shrimp larvae, was used for bioassay-guided isolation and to test for cytotoxic activity against HeLa cervical cancer cells and antioxidant activity. The ethyl acetate extract was the most toxic against the brine shrimp larvae with LC50 7.2 μg/mL at (95 % CI of 4.993/10.033), while the methanol fraction gave an LC50 346.8 μg/mL. The ethyl acetate extracts exhibited antioxidant activity in both the DPPH and FRAP with EC50 = 83.05 ± 0.06 μg/mL and (58.75 ± 0.091 μmol Fe2+ /g dry weight respectively. It also revealed cytotoxic activity against HeLa cervical cancer cells with IC50 of 17.2 ± 3.4 μg/mL. A new compound, 3-((Z)-heptadec-14-enyl) benzene -1-ol, isolated from the ethyl acetate extract exhibited a weak cytotoxic activity of 35.24 ± 3.5 μg/mL on HeLa cells. Cell cycle analysis showed that the ethyl acetate extract inhibited mitosis and induced apoptosis as evidenced by activation of caspase 3 and membrane phosphatidylserine translocation. The present results provide initial evidence that the root extract of R.natalensis contains compounds with both cytotoxic and antioxidant activity. Further studies are needed to determine activity on other cancer cell lines and to further elucidate the mechanism of cytotoxic activity.