Two new glycoalkaloids, erianosides A (1) and B (2) along with five known compounds (3-7) were isolated from the leaves of Solanum erianthum. Their structures were elucidated from analyses of spectroscopic data and all isolates were tested for in vitro cytotoxic activity against human breast cancer cell lines (BT-549, MDA-MB-231, T74D, and MCF-7). Solasonine (5) and solamargine (6) were active against the aforementioned four cancer cell lines with IC50 values of 27.26-35.89 and 5.84-10.13 mu M, respectively. Erianoside A (1) (T74D: IC50, 56.39 mu M) and solasodine (3) (BT-549 and MDA-MB-231: IC50, 59.15 and 75.63 mu M, respectively) had moderate cytotoxic effects towards some cell lines in the panel.