Two new triterpenoid estersaponins and biological activities of Pittosporum tobira 'Variegata' (Thunb.) W. T. Aiton leaves.

Two new triterpenoid estersaponins (1, 2) were isolated from the leaves of Pittosporum tobira 'Variegata' (Thunb.) W. T. Aiton, along with one known saponin (3) and one known flavonoid glycoside (4). Their structures were established by different spectroscopic methods including 1D and 2D NMR, UV, as well as ESI-MS analysis. The investigated 80% aqueous methanol extract showed significant dose dependent inhibition of acetic acid induced abdominal writhing in mice. The n-butanol fraction exerted moderate antimicrobial activity against Staphylococcus aureus and Escherichia coli. In addition, it showed in vitro antioxidant activity with IC50 value (7.3 μg/ml) lower than that of the positive control ascorbic acid (11.2 μg/ml), using DPPH free radical scavenging activity method. Evaluation of its in vitro cytotoxicity showed strong activity against breast carcinoma (MCF-7), hepatocellular carcinoma (HepG2), and colon carcinoma (HCT) cell lines.