New biphenyl derivatives from the leaves of Nicotiana tabacum and their cytotoxic activity

•Three new (1–3) biphenyls were isolated from Nicotiana tabacum.•Four known (4–7) biphenyls were also obtained from the title plant.•1–7 were tested for their cytotoxicity.•1–7 showed moderate or weak activities with IC50 values ranging from 2.8 to 9.4μM.